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The Washington Study of endodontic success and fail- ure suggests percolation of periradicular exudate into the incompletely filled canal as the greatest cause of endodontic failure. Nearly 60% of the failures in the study were apparently caused by incomplete oblitera- tion of the radicular space (see chapter 13). Dow and Ingle demonstrated in vitro the possibility of apical percolation using a radioactive isotope. 1 After filling the root canals of extracted teeth, they placed the teeth in radioactive iodine ( 131 I). In teeth with a fluid-tight seal of the apical foramen and a well-oblit- erated canal space, there was no penetration of the radioactive iodine (Figure 11-1, A). In the poorly filled canals—filled so by design—a deep penetration into the canal by 131 I was apparent in the radioautographs (Figure 11-1, B). On the basis of this study, one might hypothesize that the penetration of radioactive iodine into a poorly filled root canal in vitro is analogous to fluid percolation into the canal of in situ pulpless teeth with incomplete canal obliteration (Figure 11-2). Apical percolation may be considered a logical hypothesis. However, the role of the end products of microleakage in the production of periradicular inflammation is open to speculation. It would seem safe to assume that the noxious products leaking from the apical foramen act as an inflammatory irri- tant. The unanswered question concerns the produc- tion of irritants in the canal. It is presently speculat- ed that the transudate constantly leaking into the unfilled or partially filled canal arises indirectly from the blood serum and consists of a number of water-soluble proteins, enzymes, and salts. It is fur- ther speculated that the serum is trapped in the cul-de-sac of the poorly filled canal, away from the influences of the bloodstream, and undergoes degra- dation there. Later, when the degraded serum slowly diffuses out to the periradicular tissue, it acts as a physiochemical irritant to produce the periradicular inflammation of apical periodontitis. Such a sequence of events might well explain the paradox of the periradicular lesion associated with a noninfected pulpless tooth. Periradicular inflamma- Chapter 11 OBTURATION OF THE RADICULAR SPACE John I. Ingle, Carl W. Newton, John D. West, James L. Gutmann, Gerald N. Glickman, Barry H. Korzon, and Howard Martin Figure 11-1 A, Failure of radioactive iodine ( 131 I) to penetrate into well-filled canal. Only periradicular cementum that was not coated with sticky wax has absorbed isotope. B, Massive reaction to penetration of radioactive iodine ( 131 I) into poorly filled canal. Violent response at periapex is comparable to in vivo response to toxic canal products. Reproduced with permission from Dow PR and Ingle JI. 1 A B

Transcript of Ch11: OBTURATION OF THE RADICULAR SPACE

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The Washington Study of endodontic success and fail-ure suggests percolation of periradicular exudate intothe incompletely filled canal as the greatest cause ofendodontic failure. Nearly 60% of the failures in thestudy were apparently caused by incomplete oblitera-tion of the radicular space (see chapter 13).

Dow and Ingle demonstrated in vitro the possibilityof apical percolation using a radioactive isotope.1 Afterfilling the root canals of extracted teeth, they placed theteeth in radioactive iodine (131I). In teeth with afluid-tight seal of the apical foramen and a well-oblit-erated canal space, there was no penetration of theradioactive iodine (Figure 11-1, A). In the poorly filledcanals—filled so by design—a deep penetration intothe canal by 131I was apparent in the radioautographs(Figure 11-1, B).

On the basis of this study, one might hypothesizethat the penetration of radioactive iodine into apoorly filled root canal in vitro is analogous to fluidpercolation into the canal of in situ pulpless teethwith incomplete canal obliteration (Figure 11-2).Apical percolation may be considered a logicalhypothesis. However, the role of the end products ofmicroleakage in the production of periradicularinflammation is open to speculation. It would seemsafe to assume that the noxious products leakingfrom the apical foramen act as an inflammatory irri-tant. The unanswered question concerns the produc-tion of irritants in the canal. It is presently speculat-ed that the transudate constantly leaking into theunfilled or partially filled canal arises indirectly fromthe blood serum and consists of a number ofwater-soluble proteins, enzymes, and salts. It is fur-ther speculated that the serum is trapped in thecul-de-sac of the poorly filled canal, away from theinfluences of the bloodstream, and undergoes degra-dation there. Later, when the degraded serum slowlydiffuses out to the periradicular tissue, it acts as a

physiochemical irritant to produce the periradicularinflammation of apical periodontitis.

Such a sequence of events might well explain theparadox of the periradicular lesion associated with anoninfected pulpless tooth. Periradicular inflamma-

Chapter 11

OBTURATION OF THE RADICULAR SPACE

John I. Ingle, Carl W. Newton, John D. West, James L. Gutmann,

Gerald N. Glickman, Barry H. Korzon, and Howard Martin

Figure 11-1 A, Failure of radioactive iodine (131I) to penetrateinto well-filled canal. Only periradicular cementum that was notcoated with sticky wax has absorbed isotope. B, Massive reaction topenetration of radioactive iodine (131I) into poorly filled canal.Violent response at periapex is comparable to in vivo response totoxic canal products. Reproduced with permission from Dow PRand Ingle JI.1

A B

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tion is presumed to persist under the influence of anynoxious substance. Bacteria certainly play a major rolein the production of toxic products in the root canal.However, in the absence of bacteria, degraded serumper se may well assume the role of the primary tissueirritant. The persistence of periradicular inflammation,in the absence of bacterial infection, might thus beattributed to the continuing apical percolation ofserum and its breakdown products.

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Add a bacterial factor to this picture and the situa-tion worsens. It is embarrassing to note that Prinz stat-ed this thought nearly 90 years ago. Speaking before theSt. Louis Dental Society on September 2, 1912, Dr.Prinz stated, “If the canal is not filled perfectly, serumwill seep into it from the apical tissues. The serum fur-nishes nutrient material for the microorganisms pres-ent in the tubulii of a primarily infected root canal.’’2

As the Scandinavians have repeatedly pointed out, bac-teria are the primary source of persistent periradicularinflammation and endodontic failure.

OBJECTIVES

From this discussion, it is apparent that the preliminaryobjectives of operative endodontics are total débride-ment of the pulpal space, development of a fluid-tightseal1* at the apical foramen, and total obliteration ofthe root canal. By the same token, one must not over-look the importance of a coronal seal. Microleakagearound coronal restorations, down through the rootcanal filling, and out the apical foramen into the peri-radicular tissues is also a potential source of bacterialinfestation.

Many studies on the preparation3 and obturation4–6

of root canals, however, indicate that most fillings do notcompletely fill the root canal system. The permeability ofthe dentin-filling interface has been demonstrated by

Figure 11-2 Lateral section of endodontic failure. Gutta-perchapoint (arrow) in no way obliterates foramen. Unfilled canal spacecontains necrotic and/or bacterial debris, a severe irritant.

*The commonly used term “hermetic seal” is not accurate.“Hermetic” is defined as “airtight by fusion or sealing.” Air is not theproblem at the periapex—fluid is the problem. “Impermeable” is amore accurate term. Ramsey, WD. Hermetic sealing of root canals.JOE 1982;198:100.

Figure 11-3 Ideal termination of canal preparation and obturation. A, Apical constriction at cementodentinal junction marks end of rootcanal. From this point to anatomic apex (0.5 to 0.7 mm), tissue is periodontal. B, Photomicrograph of periapex. Small arrows at cemento-dentinal junction. Large arrow (bottom) at denticle inclusion. A reproduced with permission from Goerig AC. In: Besner E, et al, editors.Practical endodontics. St. Louis: CV Mosby; 1993. p. 46. B reproduced with permission from Brynolf I. Odontol Revy 1967;18 Suppl. 11.

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dye,7–14 radioisotope,1,15–19 electrochemical,20–22 fluoro-metric,23,24 and scanning electron microscopic examina-tion.25,26 This is only a partial listing of the vast numberof microleakage studies that have been done asendodontic research continues to seek improved sealingefficiency of new materials and techniques.

EXTENSION OF THE ROOT CANAL FILLING

The anatomic limits of the pulp space are thedentinocemental junction apically, and the pulp cham-ber coronally. Debate persists, however, as to the idealapical limit of the root canal filling.

Canals filled to the apical dentinocemental junctionare filled to the anatomic limit of the canal. Beyond thispoint, the periodontal structures begin (Figure 11-3).Under the rubric “Why Root Canals Should Be Filled tothe Dentinocemental Junction,” three early endodonticadvocates prescribed this limitation over 70 yearsago.27–29 Two of them, Orban and Skillen, wereworld-renowned dental scientists.

The dentinocemental junction is an average of about0.5 to 0.7 mm from the external surface of the apicalforamen, as clearly demonstrated by Kuttler,30 and isthe major factor in limiting filling material to the canal

(Figure 11-4). A clarification in terminology is in order.Two terms, overfilling and overextension, are oftenused interchangeably. This is not correct. Overfillingdenotes “total obturation of the root canal space withexcess material extruding beyond the apical fora-men.”31 Note the emphasis on “total obturation.”Overextension, on the other hand, may also denoteextrusion of filling material beyond the apical foramenbut with the caveat that the canal has not been ade-quately filled and the apex has not been sealed.31 It hasbeen said facetiously that “overfilling happens to you,whereas overextension happens to the other guy.”

With these definitions in mind, let it be said that anumber of dentists disagree with the contention thatthe terminus of the filling should be at the dentinoce-mental junction. They prefer instead to fill to the radi-ographic external surface of the root or just beyond.They seek to develop a small “puff” of overfilling(Figure 11-5).

Filling to the radiographic end of the root is actuallyoverfilling, for, as Figure 11-3 shows, the apical flare ofthe foramen is filled with periodontal tissue. Purposelyoverfilling to produce a periradicular “puff” is advocat-ed primarily by the proponents of the diffusion tech-nique or the softened gutta-percha technique.Ostensibly, the “puff” or “button” is designed to com-pensate for shrinkage of the filling by pulling downtightly against the apex. Although no proof exists thatthis is true, the advocates of softened gutta-percha fill-ings interpret the apical “puff” as an indicator that thegutta-percha has been densely packed into the apical

Obturation of the Radicular Space 573

Figure 11-4 Instrumentation and root canal filling beyond apicallimitation. Minor inflammatory and foreign body reaction has devel-oped in response to irritant. (Courtesy of Dr. Seiichi Matsumiya.)

Figure 11-5 Periradicular “puff” (arrows) at four portals of exit,maxillary premolar, provides assurance that canals are filled.

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preparation and that all of the aberrations, as well as thelateral and accessory canals of the root canal system,have been cleansed and filled. No accounting is given ofpostoperative discomfort. In any case, overfilled canalstend to cause more postoperative discomfort than dothose filled to the dentinocemental junction.

Many authors believe that filling just short of theradiographic apex is greatly preferred to overfilling.Filling short of the apex following pulpectomy is espe-cially recommended by Nygaard-Østby,32 Blayney,33

and most recently Strindberg.34 Horsted andNygaard-Østby reported on pulpectomies of 20 vitalhuman teeth, stating that the space between thegutta-percha-Kloropercha fillings and the tissue surfacewas filled by new connective tissue within a fewmonths.35 They claimed the same results with clinicallyhealthy and chronically inflamed pulps (Figure 11-6).The University of Washington study also found no fail-ures among those well-obliterated cases in which thefilling terminated slightly short of the apex, whereas3.85% of the failures were caused by overfilling.

Despite all of this, a high degree of success is stillachieved if overfilling occurs. Fortunately, most of theroot canal sealers currently used, as well as the

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solid-core filling materials, are eventually tolerated bythe periradicular tissues once the cements have set. Thetissue reaction that does occur can be a fibrous wallingoff of the foreign body (Figure 11-7). On the otherhand, fewer stormy postoperative reactions can beexpected if canal instrumentation and filling are limit-ed by the narrowest waist of the apical foramen.

WHEN TO OBTURATE THE CANAL

The root canal is ready to be filled when the canal iscleaned and shaped to an optimum size and dryness.Many feel that the smear layer lining the canal wallsshould also be removed. The tooth should be comfort-able. Dry canals may be obtained with absorbent pointsexcept in cases of apical periodontitis or apical cyst, inwhich “weeping” into the canal persists.

The exception to the aforementioned criteria is thecase in which mild discomfort persists. Experience hasshown that filling the root canal in such cases usuallyalleviates the symptoms. However, filling a root canalknown to be infected is risky. Ingle and Zeldow havedescribed the increase in postoperative discomfortfrom filling infected root canals.36 They also haveshown that the degree of success in a group of infectedcases was 11.2% less than that in an a priori group ofcases with negative bacteriologic cultures.37 More

Figure 11-6 Partial pulpectomy adequately obliterated to point ofamputation. Even though root canal filling is short of apex, perfecthealing has developed, as evidenced by normal pulp and periradic-ular tissue. (Courtesy of Dr. Seiichi Matsumiya.)

Figure 11-7 Tissue reaction to foreign body such as gutta-percha.(Courtesy of Dr. S.N. Bhaskar and US Army Institute of Pathology.)

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recently, Sjögren and his associates in Sweden foundthat, after 5 years, 94% of those cases exhibiting nega-tive cultures at the time they were filled were com-pletely successful. In marked contrast, only 68% of thecases filled with positive cultures were successful after5 years, a 26% difference in success rate.38

MATERIALS USED IN OBTURATION

The materials used to fill root canals have been legion,running the gamut from gold to feathers. Grossmangrouped acceptable filling materials into plastics,solids, cements, and pastes.39 He also delineated 10requirements for an ideal root canal filling materialthat apply equally to metals, plastics, and cements:

1. It should be easily introduced into a root canal.2. It should seal the canal laterally as well as apically.3. It should not shrink after being inserted.4. It should be impervious to moisture.5. It should be bacteriostatic or at least not encourage

bacterial growth.6. It should be radiopaque.7. It should not stain tooth structure.8. It should not irritate periradicular tissue.9. It should be sterile or easily and quickly sterilized

immediately before insertion.10. It should be removed easily from the root canal if

necessary.

Both gutta-percha and silver points meet theserequirements. If the gutta-percha point has a fault, itlies in its inherent plasticity, for it requires special han-dling to position it. The major fault with the silverpoint is its lack of plasticity—its inability to be com-pacted. Both must be cemented into place, however, tobe effective.

Solid-Core Materials

Gutta-percha is by far the most universally usedsolid-core root canal filling material and may be classi-fied as a plastic. To date, modern plastics have been dis-appointing as solid-core endodontic filling materials.However, new plastics are on the horizon. Silver amal-gam, used in the retrosurgical technique wherein thecanal is filled from the apex, must also be considered a“plastic” filling material.

Gutta-percha

Because modern petrochemical plastics have proved sodisappointing for canal obturation, a new interest hasdeveloped in old-fashioned gutta-percha. First shownas a curiosity in the mid-seventeenth century,

gutta-percha escaped notice as a practical product fornearly 200 years. The first successful use of the curiousmaterial seems to have been as insulation for underseacables. This was in 1848, and patents followed for itsuse in the manufacture of corks, cement thread, surgi-cal instruments, garments, pipes, and sheathing forships. Some boats were made entirely of gutta-percha.Gutta-percha golf balls were introduced by the latterpart of the nineteenth century; until 1920, golf ballswere called “gutties.’’ Gutta-percha has been known todentistry for over 100 years.40

Actually, true gutta-percha may not be the productpresently supplied to the dental profession.Manufacturers privately admit they have long used bal-ata, which is the dried juice of the Brazilian treesManilkara bidentata, of the sapodilla family. Gutta-per-cha also comes from the sapodilla family, but fromMalaysian trees, genera Payena or Palaquium.Chemically and physically, balata and gutta-perchaappear to be essentially identical; investigators in thisfield may have been given balata to test and told it wasgutta-percha. In any event, the point appears to bemoot, and either product is here called “gutta-percha.”

Chemically pure gutta-percha (or balata) exists intwo distinctly different crystalline forms (alpha andbeta) that can be converted into each other. The alphaform comes directly from the tree. Most commercialgutta-percha, however, is the beta crystalline form.40

There are few differences in physical properties betweenthe two forms, merely a difference in the crystalline lat-tice depending on the annealing and/or drawing processused when manufacturing the final product.41

Traditionally, the beta form of gutta-percha wasused to manufacture endodontic gutta-percha pointsto achieve an improved stability and hardness andreduce stickiness. However, through special processingand/or modifications to the formulation of the gutta-percha compound, more alpha-like forms of gutta-per-cha have been introduced, resulting in changes in themelting point, viscosity, and tackiness of the gutta-per-cha point. Gutta-percha with low viscosity will flowwith less pressure or stress,42 while an increase in tack-iness will help create a more homogeneous filling.Various manufacturers have introduced products totake advantage of these properties (eg, Thermafil,Densfil, Microseal).

The effect of heating on the volumetric change ofgutta-percha is most important to dentistry. Gutta-per-cha expands slightly on heating, a desirable trait for anendodontic filling material.43 This physical propertymanifests itself as an increased volume of material thatmay be compacted into a root canal cavity. Volumetric

Obturation of the Radicular Space 575

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studies show that it is possible to “overfill” a root canalpreparation when heat and vertical condensation areapplied because the volume of the gutta-percha fillingis greater than the space it occupies.44

Although the material is thought to be compressedwith force that would reduce its volume, studies haveshown that it is actually compacted, not compressed,45

and increased volumetric changes are due to heating.Unfortunately, warmed gutta-percha also shrinks as

it returns to body temperature. Schilder et al. thereforerecommend “that vertical pressure be applied in allwarm gutta-percha techniques to compensate for vol-ume changes that occur as cooling takes place.”46

Camps et al. found that, even though warm gutta-per-cha is easily compacted, the plugger must be intro-duced apically since permanent deformation is under-gone only after a 50% reduction in volume.47 This con-trasts with the use of cold gutta-percha in which animportant pressure must be applied to obtain perma-nent deformation, but the spreaders do not have to beintroduced apically since a 6% deformation is alreadypermanent. Although techniques of gutta-perchaplacement involving heating in the root canal causedreversible physical changes, no apparent changes inchemical composition take place.48

Studies of pure gutta-percha are actually rathermeaningless because endodontic gutta-percha containsonly a fraction of gutta-percha per se. A study atNorthwestern University49 of the chemistry ofgutta-percha filling points supplied by five manufactur-ers found only about 20% of the chemical compositionto be gutta-percha, whereas the 60 to 75% of the com-position is zinc oxide filler (Table 11-1). The remainingconstituents are wax or resin to make the point more pli-able and/or compactible and metal salts to lendradiopacity. On an organic versus inorganic basis,gutta-percha points are only 23.1% organic (gutta-per-

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cha and wax) and 76.4% inorganic fillers (zinc oxide andbarium sulfate).49 High zinc oxide levels were found toincrease brittleness in the points and decrease tensilestrength. These percentages of composition essentiallyhave been confirmed by a French group. However, theyfound that it is the high content of gutta-percha in thepoints that results in their brittleness.50

Gutta-percha points also become brittle as they age,probably through oxidation.51 Storage under artificiallight also speeds their rate of deterioration.52 On theother hand, they can be rejuvenated somewhat by alter-nate heating and cooling.53

Evidence of slight antibacterial activity from gutta-percha points exists54; however, it is too weak to be aneffective microbiocide. As the destruction of bacteria iskey to endodontic success, a new formulation of gutta-percha that contains iodoform, Medicated Gutta-Percha (MGP) (Medidenta, Woodside, N.Y.), has beendeveloped by Martin and Martin.55 Within the filledroot canal, the iodine/iodoform depot in the MGP coneis a biologically active source for inhibiting microbialgrowth. The iodoform is centrally located within thegutta-percha and takes about 24 hours to leach to thesurface. “The iodoform remains inert until it comes incontact with tissue fluids that activate the free iodine.”55

A canal filled with MGP gutta-percha could serve as aprotection against bacterial contamination from coro-nal microleakage reaching the apical tissue. The use ofheat during obturation does not affect either the releaseof the iodoform or its chemical composition.

Gutta-percha cones have also been introduced thatcontain a high percentage of calcium hydroxide(40–60%) (Roeko) to permit simple placement of themedicament within the canal space between appoint-ments. Once the calcium hydroxide has leached out, thepoint is no longer useful as a filling material and mustbe removed. Holland et al. have reported on the use of

Table 11-1 Mean (x- ) and Standard Deviation (SD) of Percentage Weights from Chemical Assay of theGutta-percha Endodontic Filling Materials

Gutta-percha Wax and/or Resin Metal Sulfates Zinc Oxide

Brand x- ± SD x- ± SD x- ± SD x- ± SD

Premier 18.9 ± 0.1 4.1 ± 0.2 14.5 ± 0.4 61.5 ± 0.5Mynol 19.9 ± 0.1 3.9 ± 0.2 16.2 ± 1.8 59.1 ± 2.0Indian Head 21.8 ± 0.2 1.0 ± 0.2 17.3 ± 0.3* 59.6 ± 0.1Dent-O-Lux 19.9 ± 0.2 2.8 ± 0.2 1.5 ± 0.3* 75.3 ± 0.5Tempryte 20.6 ± 1.4 2.9 ± 0.2 3.4 ± 2.1* 73.4 ± 2.0

*Colored residue found with metal sulfate.Reproduced with permission from Friedman CE, Sandrik JL, Heuer MA, Rapp GW. JOE 1977;8:305.

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an experimental calcium hydroxide containing gutta-percha cone that can be used for root canal filling.Their results indicated that these points produced animprovement in the apical sealing quality of the rootcanal filling.56

Beyond these biocide qualities, gutta-percha alsoexhibits a degree of tissue irritation, the latter probablyrelated to the high content of zinc oxide, which isknown to be an irritant.57 Wolfson and Seltzer foundearly on a severe tissue reaction to all eight brands ofgutta-percha points injected into rat skin.58

Configuration

Gutta-percha points (or cones) are supplied in twoshapes. The traditional form is cone shaped to con-form to the perceived shape of the root canal. Todaythese cones are preferred by dentists who use the warmgutta-percha/vertical compaction technique of filling.Also, because the original spreaders used in the lateralcompaction technique were shaped to match thesecone shapes and sizes, traditional cones have long beenused as the accessory cones in the lateral compactiontechnique.

The other shape of gutta-percha points is standard-ized to the same size and shape as the standardized(ISO) endodontic instruments. These points are avail-able in the standardized .02 taper as well as in increasedtaper sizes (.04, .06, etc) to correspond to the newertapered instrument sizes. Color coding the numberedpoints to match ISO instrument color has become rou-tine and it is now rare to find the standardized pointswithout these convenient markings (N. Lenz, personalcommunication). Although gutta-percha points aresupposed to be standardized according to instrumentsize, a startling lack of uniformity has been found,59 aswell as an alarming degree of deformation of the pointsin their apical third60 (Figure 11-8).

Before being used for root canal filling, gutta-perchapoints should be free of pathogenic microorganisms.Siqueira et al. studied four commonly used disinfec-tants and found that only 5.25% sodium hypochloritewas effective in eliminating Bacillus subtilis spores fromgutta-percha cones after 1 minute of contact.Glutaraldehyde, chlorhexidine, and ethyl alcohol didnot decontaminate the gutta-percha points even after10 minutes of contact.61

Silver

Silver points are the most widely used solid-core metal-lic filling material, although points of gold, iridioplat-inum, and tantalum are also available. Silver pointsmay be indicated in mature teeth with small or

well-calcified round tapered canals: maxillary first pre-molars with two or three canals, or the buccal roots ofmature maxillary molars and mesial roots of mandibu-lar molars if they are straight. In youngsters, even thesecanals are too large and too ovoid for single silver pointuse. Silver points are also not indicated for filling ante-rior teeth, single canal premolars, or large single canalsin molars.

Silver points often fail when used outside these situ-ations (Figure 11-9). These failures in judgment havegiven silver points a bad name. Seltzer and colleagueshave dramatically shown that failed silver points arealways black and corroded when removed from thecanal.62 Goldberg has further noted that corrosion maybe observed microscopically in cases previously judgedto be successful by clinical and radiographic criteria.63

Kehoe reported a case of localized argyia of the buccalgingiva, a dark-blue pigmented “tattoo” surrounded bya gray halo (Figure 11-9, C), related to severe corrosionof a failing silver point64 (Figure 11-9, D).

Gutierrez and his associates in Chile found thatcanal irrigants corrode silver points.65 Brady and delRio reported that sulfur and chlorides were detected by

Obturation of the Radicular Space 577

Figure 11-8 A, Five different brands of standardized gutta-perchapoints showing irregularities in apical one third of tip. B, Three dif-ferent brands of standardized gutta-percha points of same sizeshowing irregularities that produce variations in tip caliber.Reproduced with permission from Goldberg F et al.60

B

A

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microanalysis of failed corroded points.66 Possibly thecorrosion begins from within the canal, an aftermath ofapical microleakage.

From such studies and a good deal of clinical evi-dence, the assumption has developed that silver pointsalways corrode. This need not be true if the roundtapered point truly fits the round tapered cavity, sealingthe foramen as a cork seals a bottle (Figure 11-10). The

578 Endodontics

only cement depended on is a “flashing” between thesilver and the dentin wall. Silver has more rigidity thangutta-percha and hence can be pushed into tightly fit-ting canals and around curves where it is difficult toforce gutta-percha. In an effort to avoid the problemsinherent in silver points, yet make use of their versatil-ity, Messing suggested that points be made of titani-um.67 After 3 years, Messing, using titanium, reported

Figure 11-9 Root canal filling failure after 20 years. A, Silver point incorrectly used in mandibular premolar. Pain and swelling were firstindications of periradicular inflammation. B, Electron photomicrograph (×300 original magnification) of corroded silver point removedfrom canal seen in A. Moisture and decomposed cement were found in canal as well. C, Dark blue-pigmented lesion (argyria) surroundedby gray halo caused by leakage from silver point corrosion. D, Corroded silver point removed from lingual canal in C 10 years after inser-tion. (Electron photomicrograph, B, courtesy of Samuel Seltzer). C and D reproduced with permission from Kehoe JC.64

A

B

C

D

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three failures caused by excessive canal curvature and“tear-drop” (“zip”) perforations with leakage, casescontraindicated for either titanium or silver.67

Sealers

In addition to the basic requirements for a solid fillingmaterial, Grossman listed 11 requirements and charac-teristics of a good root canal sealer68:

1. It should be tacky when mixed to provide goodadhesion between it and the canal wall when set.

2. It should make a hermetic [sic] seal.3. It should be radiopaque so that it can be visualized

in the radiograph.4. The particles of powder should be very fine so that

they can mix easily with the liquid.5. It should not shrink upon setting.6. It should not stain tooth structure.7. It should be bacteriostatic or at least not encourage

bacterial growth.8. It should set slowly.9. It should be insoluble in tissue fluids.

10. It should be tissue tolerant, that is, nonirritating toperiradicular tissue.

11. It should be soluble in a common solvent if it is nec-essary to remove the root canal filling.

One might add the following to Grossman’s 11 basicrequirements:

12. It should not provoke an immune response in peri-radicular tissue.69–72

13. It should be neither mutagenic nor carcino-genic.73,74

Unfortunately, zinc oxide–eugenol (ZOE) paste andZOE paste modified with paraformaldehyde have beenfound to alter dog pulp tissue, making it antigenetical-ly active.75 Epoxy resin sealer (AH-26), on the otherhand, “does not produce any systemic antibody forma-tion or delayed hypersensitivity reaction.”72

As far as mutagenicity and carcinogenicity are con-cerned, Harnden73 reported that eugenol and itsmetabolites, although suspect, were uniformly negativein a bacterial mutagenicity test; hence the probabilitythat eugenol is a carcinogen is relatively low.

Formaldehyde, formalin, and paraformaldehyde, onthe other hand, are highly suspect. The US ConsumerProduct Safety Commission has issued warningsabout the hazards of formaldehyde75 following a studyon the subject by the National Academy of Sciences.76

In regard to some of the other 11 requirements orig-inally elucidated by Grossman,68 it can be said that onlypolycarboxylates and glass ionomers satisfy require-ment No. 1, good adhesion to dentin.77 Newer adhe-sives are being tested at this time, however, and someappear promising.

Obturation of the Radicular Space 579

Figure 11-10 Silver point removed from palatal canal of successfully treated molar, 7 years after treatment. No corrosive deposits are appar-ent. A, ×60 original magnification; B, ×600 original magnification. Reproduced with permission from Seltzer S et al.62

A B

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As far as requirement No. 2, the hermetic sic seal, isconcerned, the literature is replete with evaluations ofsealing effectiveness, many of them contradictory, andvirtually all questionable as to their validity.78–80 This isdiscussed later in the chapter.

Radiopacity, requirement No. 3, is provided by saltsof heavy metals and a halogen: lead, silver, barium, bis-muth, or iodine. Beyer-Olsen and Orstavik measuredthe radiopacity of 409 root canal sealers and concludedthat it would be difficult to compare radiographicallythe quality of root filling when such a variance exists inradiopacifiers.81

Requirement No. 4, dealing with particle size, wasalso investigated by Orstavik, who found sealer filmthicknesses, after mixing, ranging from 49 to 180 µm.82

There was no apparent correlation, however, betweenparticle size and film thickness. He did point out theproblems encountered with a thick film and propersealing of the primary gutta-percha point. He foundthat some “sealers may prevent reinsertion of agutta-percha point to its correct prefitted position.”82

Requirement No. 5, “It should not shrink upon set-ting,” is notoriously violated if a canal is filled withgutta-percha dissolved in chloroform. Whatever thevolume of the chloroform in the mixture, that will bethe percentage of shrinkage as the chloroform gradual-ly evaporates.83 Moreover, all of the sealers shrinkslightly on setting, and gutta-percha also shrinks whenreturning from a warmed or plasticized state. At theUniversity of Connecticut Kazemi et al. found thatZOE sealers begin shrinking “within hours after mix-ing” but that AH-26…first expanded and showed noshrinkage for 30 days.” They concluded that “significantdimensional change and continued volume loss canoccur in some endodontic sealers.”84

The admonition that sealers and filling materials“should not stain tooth structure,” Grossman’s require-ment No. 6, is evidently being violated by a number ofsealers. Van der Burgt from Holland and her associatesreported that “Grossman’s cement, zinc oxide–eugenol,Endomethasone, and N2 induced a moderateorange-red stain” to the crowns of upper premolarteeth.85 She further found that “Diaket and Tubli-Sealcaused a mild pink discoloration,” whereas “AH-26gave a distinct color shift toward grey.” On the otherhand, “Riebler’s paste caused a severe dark red stain.”Diaket caused the least discoloration.86 As far as thestaining ability of other materials is concerned, Van derBurgt found that Cavit produced “a light to moderateyellowish/green stain,” that “gutta-percha caused a mildpinkish tooth discoloration,” that “AH-26 Silver-Freeand Duo Percha induced a distinct color shift towards

580 Endodontics

grey” and that crowns filled with IRM and Dycalbecame somewhat darker. “No discolorations wererecorded for teeth filled with Durelon, Fuji glassionomer, Fletcher’s cement, or zinc phosphatecement.”87 Sealers that contain silver as a radiopacifier,such as Kerr’s Root Canal Sealer (Rickert’s Formula) orthe original AH-26, are notorious as tooth stainers. Allin all, it seems wise to avoid leaving any sealers or stain-ing cements in the tooth crown.

Grossman himself investigated the significance ofhis requirement No. 7, bacteriostatic effect of sealers.88

After testing 11 root canal cements, he concluded thatthey all “exerted antimicrobial activity to a varyingdegree,” those containing paraformaldehyde to agreater degree initially. With time, however, this latteractivity diminished, so that after 7 to 10 days theformaldehyde cements were no more bactericidal thanthe other cements.

A British group studying the antibacterial activityof four restorative materials reached much the sameconclusion regarding ZOE and glass ionomercements.89 Another study found that 10 sealers inhib-ited growth of Streptococcus sanguis and Streptococcusmutans.90 A Temple University study found thatGrossman’s Sealer had the greatest overall antibacter-ial activity, but that AH-26 was the most active againstBacteroides endodontalis, an anaerobe.91 Heling andChandler, at Hebrew University, also found AH26,within dentinal tubules, to have the strongest antimi-crobial effect over three other well-known sealers.92

The Dundee University group, working with anaer-obes, found, in descending order of antimicrobialactivity, Roth Sealer (Grossman’s) to be the best, fol-lowed by Ketac-Endo, Tubliseal, Apexit, andSealapex.93 Mickel and Wright also found Roth Sealerto be more bactericidal than the calcium hydroxidesealers and attributed the effect to the concentrationof eugenol.94 From Germany, Schafer and Bossmanreported on the efficacy of a new liquid antimicrobial,camphorated chloroxylenol (ED 84), as a good “tem-porary root canal dressing for a duration of 2 days.”For a longer term dressing, they recommended calci-um hydroxide.95

Grossman stated in requirement No. 9 that sealersshould not be soluble in tissue fluids. Smith96 andMcComb and Smith97 found a wide variance in sealersolubility after 7 days in distilled water, ranging from4% for Kerr’s Pulp Canal Sealer to much less than 1%for Diaket (Figure 11-11). Peters found after 2 yearsthat virtually all of the sealer was dissolved out of testteeth filled by lateral or vertical compaction.98

Therefore most sealers are soluble to some extent.

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The very important requirement No. 10, tissue tol-erance, will be dealt with at length later in the chapter.Suffice it to say at this time that the paraformalde-hyde-containing sealers appear to be the most toxic andirritating to tissue. A case in point is reported fromIsrael: necrosis of the soft tissue and sequestration ofcrestal alveolar bone from the leakage of paraformalde-hyde paste from a gingival-level perforation.99

Cements, Plastics, and Pastes

The cements, which have wide American acceptance,are primarily ZOE cements, the polyketones, andepoxy. The pastes currently in worldwide vogue arechlorapercha and eucapercha, as well as the iodoformpastes, which include both the rapidly absorbable andthe slowly absorbable types. Despite their disadvan-tages, pastes are applicable in certain cases. The plasticsshow promise, as do the calcium phosphate products.At present the methods most frequently used in fillingroot canals involve the use of solid-core points, that areinserted in conjunction with cementing materials.Gutta-percha and silver per se are not considered ade-quate filling material unless they are cemented in placein the canal. The sealers are to form a fluid-tight seal at

the apex by filling the minor interstices between thesolid material and the wall of the canal, and also by fill-ing patent accessory canals and multiple foramina.Dye-immersion studies have shown the necessity ofcementation, without which dye penetrates back intothe canal after compaction; this occurs with all knownsolid-core root canal–filling techniques.

Cements

Zinc Oxide–Eugenol. An early ZOE cement,developed by Rickert (Kerr Pulp Canal Sealer; KerrDental; Orange, Calif.), has been the standard of theprofession for years. It admirably met the requirementsset down by Grossman except for severe staining. Thesilver, added for radiopacity, causes discoloration of theteeth, thus creating an undesirable public image forendodontics. Removing all cement from the crowns ofteeth would prevent these unfortunate incidents.100

Pulp Canal Sealer (PCS) has more recently emergedas the favorite sealer of the warm gutta-percha, verticalcondensation adherents. However, one of its disadvan-tages was the rapid setting time in high heat/humidityregions of the world. To solve this problem, Kerrreconfigured the formula into Pulp Canal Sealer EWT(Extended Working Time) (Sybron Endo/Kerr;Orange, Calif.) that now has a “6 hour working time.”The regular-set cement is also still available. Recentapical microleakage studies have shown the regularPulp Canal Sealer (PCS) to be “significantly betterthan Roth 801 and AH26 at 24 weeks.”101Additionalresearch, comparing sealing ability between regularPulp Canal Sealer and the new EWT sealer, found nosignificant difference between the two.102

In 1958 Grossman recommended a nonstainingZOE cement as a substitute for Rickert’s formula.103

Now available as Roth’s Sealer, it has become the stan-dard by which other cements are measured because itreasonably meets most of Grossman’s requirements forcement. The formula is as follows68:

PowderZinc oxide, reagent 42 parts Staybelite resin 27 parts Bismuth subcarbonate 15 parts Barium sulfate 15 parts Sodium borate, anhydrous 1 partLiquidEugenol

This cement is available commercially as Roth’s 801(Roth’s Pharmacy, USA) or U/P Root Canal Sealer(Sultan, USA).

Obturation of the Radicular Space 581

Figure 11-11 Solubility of root canal cements. Zincoxide–eugenol cements were most soluble, and polyketones andpolycarboxylates were least soluble. Reproduced with permissionfrom McComb D and Smith D.97

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All ZOE cements have an extended working time butset faster in the tooth than on the slab because ofincreased body temperature and humidity. If theeugenol used in the preceding nonstaining cementbecomes oxidized and brown, the cement sets too rap-idly for ease of handling. If too much sodium boratehas been added, the setting time is overextended.

The main virtues of such a cement are its plasticityand slow setting time in the absence of moisture, togeth-er with good sealing potential because of the small volu-metric change on setting. Zinc eugenate has the disad-vantage, however, of being decomposed by waterthrough a continuous loss of the eugenol. This makesZOE a weak, unstable material and precludes its use inbulk, such as for retrofillings placed apically through asurgical approach.96 Other zinc oxide–type cements inuse are Tubliseal (Sybron Endo/Kerr; Orange, Calif.),Wach’s Cement (Roth’s Pharmacy, Chicago Ill.), andNogenol (G-C America; Alsip, Ill. and Japan).

As Kerr’s PCS fell into some disfavor because ofstaining, the company developed a nonstaining sealer,TubliSeal. Marketed as a two-paste system, it is quickand easy to mix. It differs from Richert’s cement inthat its zinc oxide–base paste also contains barium sul-fate as a radiopacifier as well as mineral oil, cornstarch,and lecithin. The catalyst is made up of a polypaleresin, eugenol, and thymol iodide. If the advantage ofTubliSeal is its ease of preparation, its disadvantage hasbeen its rapid set, especially in the presence of mois-ture. The company has reformulated the sealer toextend working time, and it is now available asSealapex Regular or Sealapex EWT (ExtendedWorking Time).

Wach’s Cement. Meanwhile, in the Chicago area,Wach’s cement became popular. A much more compli-cated formula, its powder base consists of zinc oxide,with bismuth subnitrate and bismuth subiodide asradiopacifiers, as well as magnesium oxide and calciumphosphate. The liquid consists of oil of clove along witheucalyptol, Canada balsam, and beechwood creosote.

The advantage of Wach’s is a smooth consistencywithout a heavy body. The Canada balsam makes thesealer tacky. A disadvantage is the odor of the liquid—like that of an old-time dental office.

At one time, medicated variations of ZOE cementswere very popular and, to some extent, remain so today.N2 and its American counterpart, RC2B, are the bestexamples, along with Spad and Endomethasone inEurope. There is no evidence that these products sealcanals better than or as well as other sealers. However,there is evidence that they dissolve in fluid and thusbreak the seal.

582 Endodontics

The one common denominator of these medicatedsealers is formaldehyde in one form or another. Sinceformalin is such a tissue-destructive chemical, it is nowonder that every cytotoxic test lists these sealers as thenumber one irritant.

It is the claim of their advocates that these sealersconstantly release antimicrobial formalin. This appearsto be true, but it is this dissolution that breaks the sealand leads to their destructive behavior (see “TissueTolerance of Root Canal Sealers, Cements, and Pastes”).

Nogenol was developed to overcome the irritatingquality of eugenol.103 The product is an outgrowth of anoneugenol periodontal pack. The base is zinc oxide,with barium sulfate as the radiopacifier along with avegetable oil. Set is accelerated by hydrogenated rosin,methyl abietate, lauric acid, chlorothymol, and salicylicacid. Removing eugenol from Nogenol evidently doesexert the sought-after effect of reducing toxicity.

It seems quite obvious that “…all these root canalcements differ widely in setting times, plasticity andphysical properties. None of the materials show her-metic [sic] sealing in the literal sense.”96

Calcium Hydroxide Sealers. In the second editionof Endodontics (1976), Luebke and Ingle first forecast anew paradigm for endodontics: a broader use of calci-um hydroxide in medicating and sealing the root canal.This is coming to pass, particularly with the introduc-tion of the calcium hydroxide sealers.

CRCS (Calciobiotic Root Canal Sealer, Coltene/Whaledent/Hygenic; Mahwah, N.J.) is essentially aZOE/eucalyptol sealer to which calcium hydroxide hasbeen added for its so-called osteogenic effect. CRCS takes3 days to set fully in either dry or humid environments. Italso shows very little water sorption.104 This means it isquite stable, which improves its sealant qualities, butbrings into question its ability to actually stimulatecementum and/or bone formation. If the calciumhydroxide is not released from the cement, it cannot exertan osteogenic effect, and thus its intended role is negated.

SealApex (Sybron Endo/Kerr; Orange, Calif.) is also acalcium hydroxide–containing sealer delivered as paste topaste in collapsible tubes. Its base is again zinc oxide, withcalcium hydroxide as well as butyl benzene, sulfonamide,and zinc stearate. The catalyst tube contains barium sul-fate and titanium dioxide as radiopacifiers as well as aproprietary resin, isobutyl salicylate, and aerocil R972. In100% humidity, it takes up to 3 weeks to reach a final set.In a dry atmosphere, it never sets. It is also the only seal-er that expands while setting.105 As with CRCS, the ques-tion remains: Is SealApex soluble in tissue fluids to releasethe calcium hydroxide for its osteogenic effect? And if so,does this dissolution lead to an inadequate seal?

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At Creighton University it was established that, in alimited surface area, such as in a minimal apical open-ing, “a negligible amount of dissolution occurred.”106

At Baylor University, however, Gutmann and Favafound in vivo that extruded SealApex disappeared fromthe periapex in 4 months.107 This dissolution did notappear to delay healing. However, the authors suspect-ed sealer dissolution may continue within the canalsystem as well, thus eventually breaking the apical seal.

If water sorption is an indicator of possible dissolu-tion, SealApex showed a weight gain of 1.6% over 21 daysin water. In contrast, CRCS gained less than 0.4%.104 Thefluid sorption characteristics of SealApex may be due toits porosity, which allows marked ingress of water.

LIFE (Sybron Endo/Kerr; Orange, Calif.), a calci-um hydroxide liner and pulp-capping material simi-lar in formulation to SealApex, has also been suggest-ed as a sealer.108

From Liechtenstein comes an experimental calciumhydroxide sealer called Apexit (Vivadent; Schaan,Liechtenstein). Australians found that it sealed betterthan SealApex and ImbiSeal.109

Japanese researchers have introduced a calciumhydroxide sealer that also contains 40% iodoform. It isnamed Vitapex (NEO Dental, Japan), and its othercomponent appears to be silicone oil.110 Iodoform, aknown bactericide, is released from the sealer to sup-press any lingering bacteria in the canal or periapex.One week following deposits in rats, Vitapex, containing45Ca-labeled calcium hydroxide, was found throughoutthe skeletal system. This attests to the dissolution anduptake of the iodoform material. No evidence is givenabout the sealing or osteogenic capabilities ofVitapex.110 NEO Dental has also produced anotherZOE-type sealer that contains not only iodoform butcalcium hydroxide as well. It is called Dentalis and isdistributed in North America by DiaDent, Canada. Itsets rapidly (5 to 7 minutes) and is very tacky.

Martin has also introduced a US Food and DrugAdministration (FDA)-approved ZOE sealer, MCS,Medicated Canal Sealer (Medidenta, Woodside, N.Y.),that contains iodoform, to go along with MGP gutta-percha points that also contain 10% iodoforml.55 Testingof MCS in vitro showed that it developed a bacterialzone of inhibition twice the size of regular ZOE sealer.

Researchers in Germany have also developed anexperimental calcium hydroxide sealer that was report-ed on favorably by Pitt-Ford and Rowe.111

Plastics and Resins

Other sealers that enjoy favor worldwide are basedmore on resin chemistry than on essential oil catalysts.

Diaket (3M/Espe; Minneapolis, Minn.), an early onefirst reported in 1951, is a resin-reinforced chelateformed between zinc oxide and a small amount of plas-tic dissolved in the liquid B-diketone. A very tackymaterial, it contracts slightly while setting, which issubsequently negated by uptake of water. In a recentdye-penetration study, the sealing ability of Diaket wassimilar to Apexit but significantly better than Ketac-Endo112 (3M/Espe; Minneapolis, Minn.).

AH-26 (Dentsply/Maillefer, Tulsa, Okla), an epoxyresin, on the other hand, is very different. It is a glue,and its base is biphenol A-epoxy. The catalyst is hexa-methylene–tetramine. It also contains 60% bismuthoxide for radiographic contrast. As AH-26 sets, tracesof formaldehyde are temporarily released, which ini-tially makes it antibacterial. AH-26 is not sensitive tomoisture and will even set under water. It will not set,however, if hydrogen peroxide is present. It sets slowly,in 24 to 36 hours. The Swiss manufacturers of AH-26recommend that mixed AH-26 be warmed on a glassslab over an alcohol flame, which renders it less vis-cous. AH-26 is also sold worldwide as ThermaSeal(Dentsply/Tulsa; Tulsa, Okla.).

Recognizing the advantages of AH-26 (highradiopacity, low solubility, slight shrinkage, and tissuecompatibility), as well as some of its disadvantages(formaldehyde release, extended setting time [24hours], and staining), the producers of AH26 set out todevelop an improved product they renamed AH PLUS(Dentsply International). They retained the epoxy resin“glue” of AH26 but added new amines to maintain thenatural color of the tooth. AH Plus comes in apaste–paste system, has a working time of 4 hours anda setting time of 8 hours, half the film thickness andhalf the solubility of regular AH26, and may beremoved from the canal if necessary. In a comparativetoxicity study, AH Plus was found to be less toxic thanregular AH-26.113 AH Plus is also sold worldwide asThermaSeal Plus (Dentsply/Tulsa; Tulsa, Okla.).

Glass ionomer cements have also been developed forendodontics. One of these is presently marketed asKetac-Endo (3M/Espe; Minneapolis, Minn.). Saitoappears to have been an early proponent of endodonticglass ionomers. He suggested using Fuji Type I lutingcement to fill the entire canal.114 Pitt-Ford in England rec-ommended endodontic glass ionomers as early as 1976.115

However, he found the setting time too rapid. Stewart wascombining Ketac-Bond and Ketac-Fil before these glassionomers were specifically formulated for endodontics.He was pleased with the result in six cases.116

At Temple University, eight different formulations ofKetac cement were researched for ease of manipulation,

Obturation of the Radicular Space 583

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radiopacity, adaptation of the dentin–sealer interface,and flow.117 Ray and Seltzer chose the sealer with thebest physical qualities: the best bond to dentin, the fewestvoids, the lowest surface tension, and the best flow. Amethod of triturating and injecting the cement into thecanal was also developed. Ketac-Endo was the outcome.

In a follow-up study, the Temple group evaluated theefficacy of Ketac-Endo as a sealer in obturating 254teeth in vivo. At the end of 6 months, they reported asuccess and failure rate comparable to that of otherstudies using other sealers.118

Their greatest concern was the problem of removal inthe event of re-treatment since there is no known solventfor glass ionomers. A Toronto/Israel group reported,however, that Ketac-Endo sealer “can be effectivelyremoved by hand instruments and chloroform solventfollowed by one minute with an ultrasonic No. 25 file.”119

More recently, leakage studies compared Ketac-Endowith AH26120,121 and Roth’s 801E and AH26.122 USNavy researchers found “Ketac-Endo allowed greater dyepenetration than Roth’s 801E and AH26.”122 On theother hand, the Amsterdam group found AH26 “leakedmore than Ketac-Endo.” They related the difference tofilm thickness: 39 microns for AH26 and 22 microns forKetac-Endo.120 In addition, the new AH product, AHPlus, has half the film thickness of regular AH26.Conversely, a Turkish group found “no statistical differ-ences” in leakage between Ketac-Endo and AH26.121

As far as toxicity is concerned, two Greek studiesfound “Ketac-Endo to be a very biocompatible materi-al.” The first study compared Ketac-Endo to Endion,which they found to be “highly toxic,”123 and the sec-ond study found only mild inflammation with Ketac-Endo, whereas TubliSeal (Sybron Endo/Kerr; Orange,Calif.) caused necrosis and inflammation as long as 4months later.124 A study from Mexico, however, foundthat Ketac Silver, the precursor to Ketac-Endo,“induces irreversible pulpal damage.”125

Experimental Sealers

In the never-ending search for the perfect root canalsealers, new fields have been invaded, including resinchemistry, which is proving so successful in restorativedentistry, and calcium phosphate cements, which are areturn to nature.

Early on, at Tufts University, a group experimentedwith a Bis GMA unfilled resin as a sealer.126 The newmaterial was found to be biocompatible but impossibleto remove.

Low-viscosity resins such as pit and fissure sealantshave also been tried as sealers but “would not seemsuitable as root canal filling materials.”127 Close adap-

584 Endodontics

tation depends on smear-layer removal, which is diffi-cult to achieve in the apical third of the canal.

At Loma Linda University, isopropyl cyanoacrylatewas found to be more adequate in sealing canals thanwere three other commercial sealers.128 However, fur-ther research was discontinued because of a lack ofacceptance by the FDA (M. Torabinejad, personalcommunication, August 1997).

A polyamide varnish, Barrier (Interdent, Inc; CulverCity, Calif.), has also been tried as a sealer but wasfound to be not as effective as ZOE.129

At the University of Minnesota, the efficacy of fourdifferent dentin bonding agents used as root canal seal-ers was tested.“No leakage was measurable in 75% of thecanals sealed with Scotchbond (3-M Corporation; SouthEl Monte, Calif.), in 70% of canals sealed with Restodent(Lee Pharmaceuticals; St. Paul, Minn.), in 60% of canalssealed with DentinAdhesit (Ivoclar; Schaan,Leichtenstein), and in only 30% of canals sealed withGLUMA130 (Bayer Dental; Laver Kusan, Germany). Thesame researchers reported the “dramatic improvementin the quality of sealing root canals using dentin bond-ing agents.”131

It seems quite probable that dentin bonding agentswill play a major role in sealant endodontics. Theirability to halt microleakage is a superb requisite forfuture investigation. The Minnesota study130 returnedto single-cone gutta-percha filling with the adhesives,the cone inserted undoubtedly to spread the adhesivelaterally and to occupy space to reduce shrinkage. Onemight even visualize a rebirth of the silver point com-bined with one of the adhesives such as Amalgambond(Parkell Co., Farmingdale, N.Y.), which adheres todentin as well as to metals.

From Zagreb, Croatia, a group used two differentcompaction methods, vertical and lateral, to condensecomposite resin with a bonding agent as a total fillingmaterial. They first developed an apical plug with bond-ing agent Clearfil (Morita Co.; Irvine, Calif. and Japan)and then photopolymerized layer on layer of compositeresin with an argon laser as they compacted the compos-ite with pluggers. They found fewer voids in their finalfilling than with lateral condensation132 (Figure 11-12).

From Siena, Italy, another group used dentin bondingagents, along with AH26 sealer and gutta-percha lateral-ly condensed, to obturate canals for leakage tests. Theyfound less leakage in those cases in which the bondingagents were used along with AH26 versus AH26 alone.133

Problems

Some obvious obstacles must be overcome, however,before these bonding agents become commercial

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endodontic sealants. First is preparation of the dentinto remove all of the smear layer. As Rawlinson pointedout, it is very difficult to remove all of the smear fromthe apical third canal, even if sodium hypochlorite andcitric acid are used with ultrasonic débridement.127

A second obstacle is radiopacity. Radiopaquing metalsalts must be added to the adhesive, and this is sure toupset the delicate chemical balance that leads to poly-merization.134 All of the bonding agents are very tech-nique sensitive, and many do not polymerize in thepresence of moisture or hydrogen peroxide.135 Thethird problem is placement: Which delivery system willbest ensure a total, porosity-free placement?136 A finalobstacle is removal in the event of failure. These resinspolymerize very hard, all the more reason to place agutta-percha core allowing future entry down the canal.

Calcium Phosphate Obturation

The possibility that one could mix two dry powderswith water, inject the mixture into a root canal, andhave it set up as hard as enamel within 5 minutes isexciting, to say the least. And yet just such a possibilitymay be emerging.

Developed and patented at the American DentalAssociation (ADA) Paffenbarger Research Center at theNational Institute of Standards and Technology by Drs.W. E. Brown and L. C. Chow and their associates, calci-um phosphate cements might well be the future idealroot canal sealer, long sought but never achieved.137,138

In mixing two variations of calcium phosphate withwater, Brown and Chow demonstrated that hydroxyap-atite would form.The pros and cons of calcium phos-phate (hydroxyapatite) obturation is discussed in

greater detail at the end of this chapter (see “A NewEndodontic Paradigm”).

Sealer Efficacy

Hovland and Dumsha probably summarized it best:“Although all root canal sealers leak to some extent—there is probably a critical level of leakage that is unac-ceptable for healing, and therefore results in endodon-tic failure. This leakage may occur at the interface of thedentine and sealer, at the interface of the solid core andsealer, through the sealer itself, or by dissolution of thesealer.”139 And one might add, “microleakage from thecrown down alongside even a well-compacted root fill-ing.” The authors went on to find that Sealapex was nodifferent after 30 days than TubliSeal or Grossman’sSealer when it comes to leakage.139

No question, there is a variance in the impermeabil-ity of the many sealers on the market. The literature isreplete with test after test, most done without prejudicebut some done to promote a product. Microleakageresearch can be “rigged” to prove a point. “Should I useradioisotopes, or should I use India ink with its largeparticle size? Should I use methylene blue or should Iuse bacteria larger than the tubuli? Should I allow thesealer to set on the bench top or in 100% humidity?Should I test immediately, at 24 hours, 1 week, 1month? Should the tests be done under normal atmos-pheric pressure or under vacuum? Should I centrifugethe test pieces? Should I remove the smear layer?” All ofthese factors have been shown to affect sealabilityresults materially, to favor one product over another.

In choosing a sealer, factors other than adhesionmust be considered: setting time, ease of manipulation,

Obturation of the Radicular Space 585

Figure 11-12 A, Apical bonding plug of Clearfil. Margin between bonding plug and composite filling can be seen clearly. B, Bundles of theresin tags remaining at the composite replica after the dentin was dissolved in vitro. Reproduced with permission from Anic I et al.132

A B

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antimicrobial effect, particle size, radiopacity, proclivi-ty to staining, dissolvability, chemical contaminants(hydrogen peroxide, sodium hypochlorite), cytotoxici-ty, cementogenesis, and osteogenesis.

Therefore, rather than quoting from the endless listof reports, each one suppressing or refuting another, aresumé will be presented and a long list of referencesprovided for perusal by the interested student.

Resumé of Adhesion. All presently available seal-ers leak; they are not impermeable. That is the firstcaveat. The second is that some leak more than others,mostly through dissolution. The greater the sealer/peri-radicular tissue interface, that is, apical perforations orblunderbuss open apices, the faster dissolution takesplace. It goes without saying that readily dissolvingsealers are not indicated in these cases.

Zinc Oxide, Calcium Hydroxide-Type Sealers. Ina 2-year solubility study, Peters found that ZOE sealerwas completely dissolved away.98 This fact alone shouldcause one to question the advisability of totally fillingthe canal with ZOE cement.

One might think that first lining the canal with var-nishes such as Barrier129 or Copalite140 might improvethe seal, but neither does.

On the basis of leakage studies alone one would behard pressed to favor one of the ZOE or zinc oxide-cal-cium hydroxide sealers over the others. Kerr’s PulpCanal Sealer (Rickert’s), Nonstaining Root Canal Sealer(Grossman’s), Wach’s Sealer, TubliSeal, Nogenol, CRCS,SealApex, Vitapex, Apexit, or even Dycal or Life, allappear to “be a wash” when numerous studies areexamined.104,112,120–122,132,133,141–147 A study compar-ing the newer Kerr Pulp Canal Sealer EWT (ExtendedWorking Time) versus the original Pulp Canal Sealerfound no significant difference in microleakage.102

Moreover, recent studies comparing Pulp Canal Sealer(PCS) with Roth 801 and AH26 found PCS a “signifi-cantly better” sealant.101

The reports are not as favorable, however, for theparaformaldehyde-containing sealers N2, RC2B, Spad,and Endomethasone. Sargenti has asserted that oblitera-tion, along with disinfection, is important for success.148

On the other hand, he has stated that it is “not mandato-ry to have a compact root canal filling.”149 He also claimsthat N2 is not resorbed from the canal but is slowlyabsorbed from the periradicular tissues, an action he calls“semi-resorbable.”149 At another time and place, he mod-ifies the statement by saying that N2 is “practically non-resorbable from the canal.”148 Yates and Hembree foundN2 to be the least effective sealer when compared withTubliSeal or Diaket after 1 year.143 Block and Langelandreported 50 failed cases treated with N2 or RC2B.150

586 Endodontics

More recent studies relating to zinc oxide-base sealers(and those previously referenced) have found essentiallythe same results for ZOE and calcium hydroxide sealersolubility,96,98,105,106,110 leakage,104,108,109,127,139,141,153–159

and bacterial inhibition.88,91,151,160,161

Despite their deficiencies, ZOE cements and theirvariations continue to be the most popular root canalsealers worldwide. But they are just that, sealers, andany attempt to depend on them wholly or in great partmaterially reduces long-term success. That is the prin-cipal reason why silver points failed—too little solidcore and too much cement in an ovoid canal (seeFigure 11-9, A).

If the apical orifice can be blocked principally bysolid-core material, success is immeasurably improvedover the long term, if not for a lifetime.162 On the otherhand, in every study in which obturation without seal-ers is attempted, the leakage results are enormouslygreater. Sealers are necessary! Researchers agree, how-ever, that thorough cleaning and shaping of the canalspace are the key to perfect obturation.

Plastic and Resin-Type Sealers. It seems reason-able to assume that plastics, resins, and glues should bemore adhesive to dentin and less resorbable than themineral oxide cements. But they have not proved to bedramatically so. In one study, AH-26 was found com-parable to ZOE sealer but better than six others.141

In another study, AH-26 and Diaket were “foundsatisfactory as sealers” along with all the ZOE prod-ucts.142 Another study found Diaket less effective thanTubliSeal but better than N2.143

In a recent Australian study, however, AH-26 wasfound to have better sealing capabilities than were threeother cements: Apexit, Sealapex, and TubliSeal.108,109 InNew Zealand, however, Sealapex outperformed AH-26up to the twelfth week, but there was no significant dif-ference after that time.158

As far as the new glass ionomer cement, Ketac-Endo,is concerned, Ray and Seltzer found it superior toGrossman’s Sealer,117 but others found it difficult toremove in re-treatment.118 More recently, Dutchresearchers found Ketac superior in sealing to AH26.120

On the other hand, US Navy researchers found Roth’s801E and AH26 superior to Ketac Endo.122 Moreover,one Turkish group found Apexit and Diaket superior toKetac,112 but a second Turkish group found no differ-ence.121 It would appear the “jury is still out” on thesealing ability of Ketac Endo.

The early leakage reports on the adhesives usedexperimentally as root canal sealers are most encourag-ing. A 1987 report, when adhesives were in their infan-cy, placed Scotchbond first, with “no leakage measura-

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ble in 75% of the canals” and GLUMA last, with 30%showing no leakage.130,131 Adhesives today are in theirthird and fourth generations, far superior to the initialresins. Also, there are adhesives such as C & BMetabond (Parkell Co., USA) or All Bond (BiscoProducts, USA) that actually polymerize best in a moistenvironment. Canals obturated for leakage studies withlaterally condensed gutta-percha sealed with a combi-nation of dentin bonding agents plus AH26 versusAH26 alone were to be found to be superior.133

A thoroughly modern approach of sealing the apicalforamen with a resin bond called Clearfil (Morita Co.;Irvine, Calif.), followed by obturation with a compositeresin condensed laterally as it was being photopoly-merized in the canal with an argon laser, layer by layer,shows promise for the future (see Figure 11-12).132

With any use of dentin adhesives and/or compos-ite resin, it is imperative that the smear layer beremoved so that the hybrid layer may form againstthe dentin and the adhesive is able to flow into thedentinal tubuli (see Figure 11-12, B). Once again, thedifficulty of removing the smear layer in the apicalregion must be emphasized.127

Experimental Calcium Phosphate Sealers (CPC).Already, the early reports on Japanese apatite sealersfind them comparable to Sealapex but better sealantsthan two other ZOE cements.163

Studies emanating from the A.D.A. PaffenbargerCenter find calcium phosphate cements very praise-worthy for their sealing properties as well as for theirtissue compatibility. In one study, they proved bettersealants than a ZOE/gutta-percha filling.164 In anotherstudy, researchers found that the apatite injectablematerial “demonstrated a uniform and tight adaptationto the dentinal surfaces of the chambers and root canalwalls.” CPC also infiltrated the dentinal tubules.165

Since these sealers set as hydroxyapatite, one must beaware that they are very difficult, but not impossible, toremove from the canal.

Tissue Tolerance of Root Canal Sealers,Cements, and Pastes

Without question, all of the materials used at this junc-ture to seal root canals—gutta-percha, silver, the seal-ers, cements, pastes, and plastics—irritate periradiculartissue if allowed to escape from the canal. And, if placedagainst a pulp stump, as in partial pulpectomy, theyirritate the pulp tissue as well. The argument seems tobe not whether the tissue is irritated when this happensbut rather to what degree and for how long it is irritat-ed, as well as which materials are tolerable or which areintolerable irritants.

At present, four approaches are being used to evalu-ate scientifically (as opposed to empirically) the toxiceffects of endodontic materials: (1) cytotoxic evalua-tion, (2) subcutaneous implants, (3) intraosseousimplants, and (4) in vivo periradicular reactions. Thestudies done on the toxicity of the materials in questionare categorized into these four evaluative methods.

Cytotoxic Evaluation. Cytotoxic studies are doneby measuring leukocyte migration in a Boyden cham-ber; by measuring the effect that suspect materials ortheir extracts have on fibroblasts or HeLa cells in cul-ture; or by using radioactively labeled tissue culturecells, or tissue culture–agar overlay, or a fibroblastmonolayer on a millipore filter disk. The results arequite similar.

The numerous cytotoxic evaluations may be summa-rized by stating that a disappointing number of today’ssealers are toxic to the very cells they have been com-pounded to protect. Some of them are toxic when firstmixed, while they are setting over hours, days, or weeks,and some continue to ooze noxious elements for years.This is, of course, caused by dissolution of the cement,thus releasing the irritants. All of the zinc oxide-typesealers, for example, gradually dissolve in fluid, releasingeugenol, which Grossman, in 1981, pointed out “is aphenolic compound and is irritating” (L.I. Grossman,personal communication, August 1981). More recently,this has been confirmed by the group in Verona, Italy.166

Chisolm introduced zinc oxide and oil of clove(unrefined eugenol) cement to dentistry in 1873.167

One would think that after 125 years something lesstoxic would be the favorite root canal sealer.167 Eugenolis not only cytotoxic but neurotoxic as well.168

Zinc oxide and eugenol, even when calcium hydrox-ide is added to the mixture, has been found universallyto be a leading cytotoxic agent.168–181 Removing eugenol(or any of the essential oils) from the mixture greatlyreduces the toxicity. Witness the spectacular differencesin cytotoxicity when unsaturated fatty acids are substi-tuted for eugenol and/or eucalyptol in sealers such asNogenol or experimental Japanese sealers.105,182,183

Eugenol alone is not the only culprit in ZOE irrita-tion. Zinc oxide itself must also be indicted. Early on,Das found zinc oxide to be quite toxic.57 More recent-ly, Meryon reported that the cytotoxicity of ZOEcement may be based more on the possible toxic effectof zinc ions.184 Maseki et al. also indicated that zincmight be a major offender when they found that dilu-tions of eugenol released from set cement allowed via-bility of 75% of their test cells.185

Toxicity from zinc ions may well extend beyond thatfound in sealers. In testing the toxicity of gutta-percha

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points, Pascon and Spångberg concluded that all brandsof points were “highly cytotoxic” and further thatalthough “…pure raw gutta-percha was nontoxic, zincoxide…showed high toxicity.” The toxicity of gutta-per-cha points was attributed to leakage of zinc ions into thefluids.”186 Adding calcium hydroxide to ZOE-typecements mollifies their toxicity somewhat.178,179

If one were forced to classify popular ZOE-type seal-ers from worst to best as far as cytotoxicity studies areconcerned, one would have to rank the pure ZOE seal-ers as worst: Grossman’s and Rickert’s, followed byWach’s and TubliSeal, Sealapex, CRCS, and finallyNogenol,183 although there is not universal agreementon this total ranking. At Loma Linda University, forexample, TubliSeal was found the least toxic followedby Wach’s and Grossman’s,175 whereas at Connecticut,Wach’s ranked ahead of TubliSeal.174 Later at theUniversity of Connecticut, however, researchers report-ing in vitro studies found TubliSeal to be “virtuallynon-toxic at all experimental levels.”177 In marked con-trast, a Greek group reported in vivo studies showingTubliSeal exhibited “severe inflammation and necrosis”

as long as 4 months later.124 The same group also foundApexit (a calcium hydroxide additive sealer) and Kerr’sclassic Pulp Canal Sealer (ZOE) remained as irritantsover a 4-month period.187 Researchers in India alsofound TubliSeal severely toxic at 48 hours and 7 daysbut not so at 3 months.188

An extensive study in Venezuela found that CRCS(ZOE-calcium hydroxide additive) was the least cytotox-ic against human gingival fibroblasts, followed byEndomet and AH26. They also reported that MTA(Dentsply/Tulsa; Tulsa, Okla.) root-end filling materialwas not cytotoxic.189 Another study of calcium hydrox-ide-containing sealers found that, with Sealapex, “noinflammatory infiltrate occurred,” whereas with CRCS, a“moderate inflammatory infiltrate occurred.”Inflammation “of the severe type” accompaniedApexit.190

Paraformaldehyde-containing sealers “are some-thing else.” Not only do they generally contain zincoxide and eugenol, but they also boast 4.78 to 6.5%highly toxic paraformaldehyde. Virtually every cytotox-ic study on N2, RC2B, Traitment SPAD,Endomethasone, Triolon, Oxpara, Riebler’s paste, andso forth finds these materials to be the most toxic of allthe sealers on the market, bar none.171,172,191 This isdiscussed further later in the chapter.

Once again one must bear in mind that the resorba-bility, the dissolvability of all of the zinc oxide sealers,allows them to continue to release their toxic elementsand to “break their seal.” Augsburger and Peters fol-

588 Endodontics

lowed 92 cases for up to 61⁄2 years after the canals hadbeen overfilled with standard ZOE (Grossman’s-typesealer). “In no recall 50 months or longer did materialremain in the periradicular tissues” was their conclu-sion. In 12 cases, “…careful evaluation of the radi-ographs of these cases convinced the authors that seal-er had also been absorbed from within the canal.”192

Cytotoxic studies on the plastics and resins revealmuch the same results as with the zinc oxide-typecements. For example, some have found AH-26, theepoxy resin, the most toxic of the resins tested,183 andsome found it the least toxic. In the latter study, Diaket(and TubliSeal) showed moderate cytotoxic effect.193 Incontrast, both studies found that formaldehyde-con-taining sealers were highly toxic.183,193

Early on, a US Navy study found AH-26 the leasttoxic, as did a study at Tennessee.169,172 Again, Diaketwas in between. Swedish dentists reported a “mildresponse using AH-26.”194 In Buenos Aires, AH-26 wasfound to have a moderate effect and Diaket a markedlytoxic effect, both at the end of 1 hour.195 AH-26,remember, releases formaldehyde as it sets. Both ofthese resin sealers were much less toxic, however, thanthe ZOE control. Statistically significant were the verymild effects of glass ionomer endodontic sealer.195

Newer formulations—AH Plus and Ketac Endo—have had cytotoxic and genotoxic studies done.113,123

AH Plus was compared with its original product, AH26, and in an in vitro test “caused only slight or no cel-lular injuries” and did not cause any genotoxicity ormutagenicity.113 In a study done in Greece, Ketac Endo“proved to be a very biocompatible material, whereasEndion was highly cytotoxic.”123

Subcutaneous Implants. Subcutaneous implantsof root canal sealers, to test their toxic effects, are doneeither by needle injection under the skin of animals, orby incision and actual insertion of the product, eitheralone or in Teflon tubes or cups. Freshly mixed mate-rial may be implanted, allowing it to set in situ, orcompletely set material may be inserted to judgelong-term effects.

The results are what one would expect from the cyto-toxicity studies. Eugenol, as all of the essential oils, is atissue irritant,196–198 particularly during initial set.104

The long-term results are also not promising.199,200

As Tagger and Tagger observed after 2 months, “…themore severe subcutaneous tissue reaction to the zincoxide-eugenol sealer was probably due to the instabili-ty of the material, which slowly disintegrated in contactwith tissue moisture.”201,202

At Northwestern University Nogenol proved to bebetter tolerated initially than TubliSeal or Richert’s

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sealer, but at 6 months the effects of TubliSeal wereworse and the effects of Richert’s (Kerr’s RCS) andNogenol were the same.104 Both contain zinc oxide.

Initial inflammation surrounding implants ofSealApex and CRCS, the calcium hydroxide sealers,appears to be resolved at 90 days.203 Yesilsoy foundSealApex caused a less severe inflammation reactionthan did CRCS. “Both Grossman’s ZOE sealer andCRCS did not have overall favorable histologic reac-tions.”203 Japanese researchers, announcing a new cal-cium hydroxide sealer, Vitapex, which also containsiodoform and silicone oil, stated that granulation tissueformed around the implanted material and a nidus ofcalcification then developed within this tissue.204

AH-26 elicited “no response at 35 days” in onestudy205 and was “well tolerated” at 60 days in anoth-er.126 Without question, N2 and other paraformalde-hyde/ZOE cements are consistently the most toxic.205,206

Tissue-implantation ranking of endodontic sealerswould again have to list Nogenol, then AH-26, SealApex,and TubliSeal. CRCS, along with the ZOE sealers, wouldrank higher in toxicity, and the formaldehyde cementsrank as unacceptable. A recent comparative study foundthe formalin-containing cements caused faster and moreprolonged nerve inhibition and paresthesia.207

Osseous Implant. Surprisingly, sealers implanteddirectly into bone evoke less inflammatory response thanthese same cements evoke in soft tissue. From Marseillecomes a report of two ZOE sealers implanted into rab-bits’ mandibles. At 4 weeks, both sealer implants showed“slight to moderate reactions—no bone formation orbone resorption.” At 12 weeks, there were “slight to veryslight reactions—bone formation in direct contact withthe sealers—and bone ingrowth into the implant tubes.”Part of the implanted sealer was absorbed, andmacrophages were loaded with the sealer.208

A US Army group found essentially the same as theFrench group.209 When Deemer and Tsaknis overfilledthe tubes, “the overfillings did not significantly com-promise the healing of the rat intraosseous tissue.”However, they noted “the irritating properties of unsetGrossman’s sealer.”210

In Argentina, Zmener and Dominguez tested glassionomer cements in dog tibias and stated that at 90days “the inflammatory picture had resolved with pro-gressive new bone formation.”211

Again, the paraformaldehyde-containing cementscame off second best.212–214

There is not enough evidence to rank cementsimplanted into bone. However, one must be impressedwith the mild-to-stimulating reactions that are report-ed in bone.

In Vivo Tissue Tolerance Evaluations. There is noquestion that the ideal method of testing a drug, a sub-stance, or a technique is in vivo in a human subject.Unfortunately, human experimentation is often dan-gerous, costly, and unethical, and therefore, for themost part, animals are substituted. It can also be saidthat the closer one rises up the phylum tree to Homosapiens, the more valid the experiment: Monkeys arebetter than dogs, and pigs, believe it or not, are betterthan cats.

In any event, many of the earlier studies were doneon rats. This was tiny meticulous root canal therapycompared with the treatment of human beings.Erausquin and Muruzabal, working in Buenos Aires,performed the seminal in vivo research on tissue toler-ance to sealers with hundreds of tests on techniquesand materials.215 They concluded that all of the com-mercial root canal sealers were toxic, causing extensiveto moderate tissue damage as soon as they escapethrough the foramen (Figure 11-13). In all honesty,however, the authors did believe that periradicularnecrosis may be due in part to an infarct caused bypressure obstruction of the region’s vessels.216 Necrosisof the periodontal ligament provoked necrosis in theadjacent cementum and alveolar bone as well (Figure11-14). In the rat, the periodontal ligament regenerat-ed within 7 days if toxic irritation did not continue.

In comparing the various sealers, Erausquin andMuruzabal found that straight ZOE cement was “high-ly irritating to the periradicular tissues and causednecrosis of the bone and cementum.”217 Inflammationpersisted for 2 weeks or more. Finally, the ZOE becameencapsulated. Much the same inflammatory reactionwas observed at the US National Bureau of Standardswhen monkey teeth were overfilled with ZOEcement218 (Figure 11-15).

In a further study, Erausquin and Muruzabel studiedother ZOE-based cements. All of the cements, if thecanal was overfilled, “showed a tendency to beresorbed” by phagocytes. Grossman’s Sealer and N2both provoked severe inflammatory reactions, andRickert’s sealer caused moderate infiltration. The mostsevere destruction of the alveolar bone, however, wascaused by poor débridement and poor filling of thecanals. The least reaction was found when the canalwas not overfilled.215

The tissue reactions to overinstrumentation and over-filling noted by Erausquin and Muruzabal were con-firmed by Seltzer and colleagues.219 In all cases, they foundimmediate periradicular inflammation in response tooverinstrumentation. When the root canals were filledshort of the foramen, the reactions tended to subside

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590 Endodontics

Figure 11-13 Periradicular tissue reaction to overfilling of rat’s teeth. A, Filling with Procosol Nonstaining Sealer (zinc oxide–eugenol) 1day postoperatively. Polymorphonuclear leukocytes have invaded even crack in cement. B, Filling with zinc oxide–eugenol cement 4 dayspostoperatively. Early polymorphonuclear leukocyte infiltration in reaction to material is apparent. Reproduced with permission fromErausquin J, Muruzabal M. Arch Oral Biol 1966;11:373.

Figure 11-14 Periradicular tissue reaction to overfill-ing with N2 formalin cement, 1 day postoperatively.N2 protruding beyond apical foramen has causedcompression of periodontal ligament. Reproducedwith permission from Erausquin J, Muruzabal M. ArchOral Biol 1966;1:373.

A B

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within 3 months and complete repair eventually tookplace. In contrast, the teeth with overfilled root canalsexhibited persistent chronic inflammatory responses.There was also a greater tendency toward epithelial prolif-eration and cyst formation in the overfilled group.Another South American group reported on dog peri-radicular specimens overfilled with SealApex, CRCS, andZOE. All responded with chronic inflammation.220

The least irritating of the cements tested by Erausquinand Muruzabal were Diaket and AH-26. Following over-filling with these sealers, the “inflammation was general-ly very mild.” Diaket, which showed a marked tendencyto be projected beyond the apex, became readily encap-sulated (Figure 11-16). AH-26, on the other hand, wasresorbed instead (Figure 11-17). The researchersobserved, “when a foreign body is not too irritating, itbecomes either resorbed or encapsulated by the body”(see Figure 11-17). Both of these processes occurred inteeth filled with Diaket and AH-26.221

More recently, Norwegian researchers tested AH26against Endomethasone, Kloropercha, and ZOE. At 6months they concluded that “the periradicular reactionto the endodontic procedures and to the materials waslimited.”222 On the other hand, the University ofConnecticut group found long-term (2 or 3 years) dif-ferences, ranking AH26 as a mild irritant, ZOE as mod-erate, and Kloropercha as severe.223

One must remember that gutta-percha points them-selves can be a periradicular tissue irritant,186,224,225 aswell as an allergen.226 Moreover, solvents such as chlo-roform, eucalyptol, and xylol can also act as irritants.227

One must conclude that periradicular tissue reac-tion to all of the cements will at first be inflammatory,but as the cements reach their final set, cellular repairtakes place unless the cement continues to break down,releasing one or more of its toxic components.

In retrospect, one must not overlook the casual obser-vation made by the group at Tufts University: “There

Obturation of the Radicular Space 591

Figure 11-15 Monkey study, periradicular area, 2 months after ZOE Grossman Sealer overfill (Gs). A, Acute inflammation with giant cells(Gc) and necrotic bone sequestration (SEQ). B, Marked acute inflammation. Polymorphonuclear leukocytes predominate. Reproduced withpermission from Hong YC et al.218

A B

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were several small well-encapsulated areas of mildinflammation that seemed to be associated with apicalramifications that were not cleaned and that containednecrotic debris.”224 Although arborization of the pulp atthe periapex is more apt to happen in dogs and monkeysthan in humans, one cannot blink away the fact that afinal filling is no better than its preparation, and ifnecrotic and infected dentin and debris are left in place,the case stands a greater chance of eventual failure.

One can summarize the discussion on root canalsealers by repeating a statement made more than 100years ago by Dr. A. E. Webster of Toronto: “It would

592 Endodontics

seem that the dental profession has not yet decidedupon a universal root canal filling material.”228

The N2/Sargenti Controversy. The term N2, asused here, is a code word for formaldehyde-containingendodontic cements. Actually, formaldehyde is a gas,whereas the forms used in dentistry are variations offormalin, the aqueous solution, or paraformaldehyde, awhite crystalline polymer.

N2 itself contains 6.5% paraformaldehyde, as does itsUS counterpart, RC2B. Other paraformaldehyde/for-malin-containing cements, popular in Europe, such asEndomethasone, Riebler’s Paste, or the SPAD products,may contain more or less than 6.5% formaldehyde. Allof them are toxic.

Legal Status in the United States. The controversyswirling around N2 and RC2B deserves special discus-sion. The use of these cements, recommended primari-ly by members of the American Endodontic Society (agroup of general dentists), has become a cause célèbre,pitting endodontist against generalist, academicianagainst practitioner. Along with these cements comes amethod of practice—the so-called “Sargenti Method.”

The method and Sargenti have been imported fromSwitzerland, but the N2 cement was barred at the bor-ders by the FDA in about 1980. To evade the importa-tion ban, disciples of Sargenti developed their own(and very similar) cement powder, RC2B. This wasalso banned under an FDA order that stated that theAgency “will take immediate regulatory action to stopthe commercial manufacture and distribution of N2type drugs” (R. J. Crout, personal communication,June 19, 1980).

Figure 11-16 A, Moderate overfilling with Diaket 15 days postoperatively. Debris from instrumentation is to right of apex and black fill-ing. B, High-power (×22 original magnification) view of Diaket and periapex. Loose connective tissue, abundance of fibroblasts, and somemacrophages and giant cells are apparent. Dentinal debris (right border) is also being attacked by macrophages. Reproduced with permis-sion from Erausquin J and Muruzabal M.221

Figure 11-17 Fragments of AH-26 scattered throughout periradic-ular tissue 30 days postoperatively, indicating resorption of sealer.Giant cells surrounded large fragment of AH-26. Reproduced withpermission from Erausquin J and Muruzabal M.221

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The FDA pointed out, however, that they do not reg-ulate the practice of dentistry and that “an endodontistor a ‘general dentist’ may use the N2 product them-selves or arrange to have a supply obtained by prescrip-tion for that individual patient.” The dentist, however,should recognize that he is responsible for the conse-quences of the use of N2 within his practice (R. J.Crout, personal communication, June 19, 1980).

The basis for these actions and this warning is thestatement,“The Food and Drug Administration has longheld, and still does, that N2 has not been demonstratedto be safe and effective for use in root canal therapy” (R.J. Crout, personal communication, June 19, 1980).

As late as 1992, the FDA was still warning dentiststhat “…the N2 material is considered to be an unap-proved new drug—and may not legally be imported ordistributed in interstate commerce…,”229 and in 1993an advisory panel to the FDA rejected new drug appli-cation No. 19-182 submitted by N2 ProductsCorporation of Levittown, Pennsylvania.230

This action follows on the heels of jury awards of$250,000 in one case and $280,000 in another topatients injured by overextension of N2 into the peri-radicular tissues of two female patients.229,231

Paralegally, the Council on Dental Therapeutics ofthe American Dental Association reissued a resolutionagainst paraformaldelyde sealers that concluded “thatthe FDA has not approved any products with this for-mulation, [so] the Council cannot recommend the useof these products at this time.”232 This report but-tressed two previous negative pronouncements byCouncil in 1977 and 1987.233,234

At the state level, the Florida Board of Dentistry hasbanned “Sargenti cement, charging that use of the fillingmaterial falls short of the minimum standard of (den-tal) care in Florida.”235 This action was precipitated by anumber of lawsuits, including an out-of-court settle-ment for $1,000,000 to a woman horribly disfiguredafter paraformaldehyde paste was misused (R. Uchin,personal communication, September 22, 1992).

The American Association of Endodontists has alsoissued a position statement condemning the use ofparaformaldehyde sealers.236

Paraformaldehyde Toxicity. As initially com-pounded, N2 was a ZOE cement containing 6.5%paraformaldehyde as well as some lead and mercurysalts. Concern over lead and mercury transport via thebloodstream to vital organs237–247 forced the Americanproducers of the N2 lookalike, RC2B, to drop the heavymetals. However, in no way would they reduce the toxicparaformaldehyde from the formula. A myriad of dam-aging research papers—in vitro, in vivo, clinical—

denouncing these products, has been published in thelast 25 years from all over the world.248–256 Pitt-Fordfound, for example, that N2 and Endomethasonecaused a universal ankylosis and root resorption ofdogs’ teeth filled, but not overfilled, with these toxicproducts.250

The two most definitive in vivo studies on the effects ofparaformaldehyde were done at Indiana University.257,258

In a 1-month study using monkeys, researchers foundapical periodontitis around 7 of 9 apices and “a granulo-ma with considerable loss of bone around another” whenRC2B was applied to 10 inflamed pulps, as recommend-ed by Sargenti. The “treated” pulps were in no bettershape than the untreated inflamed controls.257

At 6 months and 1 year, severe periradicular inflam-mation with liquefaction necrosis developed afterRC2B was applied to coronal pulps with pulpitis. Noneof the control teeth had periradicular inflammation.258

When RC2B was used to fill well-prepared root canals,previously allowed to become necrotic, the results wereeven more overwhelming: osteomyelitis at 6 monthsand abscess formation, even cyst formation, withinmassive periradicular lesions at 1 year (Figure 11-18).The cases “treated” with RC2B were no better, or wereworse, than the necrotic canal cases left open to salivarybacteria (Figure 11-19). Around a fragment of RC2Bfound in the tissue, advanced inflammation, necrosis,and even osteomyelitis were present (Figure 11-20). Atthe National Bureau of Standards, much the samedestruction was found (Figure 11-21).218

The most important constituent in any of thesecements (N2, RC2B, Endomethasone, SPAD) is theparaformaldehyde, according to their proponents. As amatter of fact, Sargenti allows for the removal of anyingredient from the powder except paraformalde-hyde.148 Unfortunately, it is this toxic product, uniqueto these cements, that causes the destruction. It is itsrelease, as the sealers are resorbed, that allows for theirdestructive behavior. Neiburger reported a case show-ing radiographic disappearance of RC2B from the peri-apex within 5 weeks.259 The Indiana group notedresorption of RC2B within 1 month.257

Nerve Damage from Paraformaldehyde. It haslong been recommended by its proponents that N2 beplaced in the canal with a fast-spinning Lentulo spiral.This is a perfectly reasonable approach, but one has toknow when enough is enough. Sargenti warns that,without great care, overfilling is likely with this tech-nique. He does not say, however, how very damagingsuch overextension will be.148 Periradicular destructionwas shown in the Indiana studies.257,258 Also, “the ADACouncil on Dental Therapeutics and Devices has

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594 Endodontics

Figure 11-18 N2/RC2B formalin cement study. A, Control specimen, pulp necrosis 3 months standing. Apical granuloma with epithelialproliferation. B, Osteomyelitis 6 months after treatment of necrotic canal with RC2B. Areas of necrotic bone within dense inflammatory infil-trate. C, Apical cyst developing 6 months after treatment of necrotic canal with RC2B. Note epithelial lining within dense inflammatory infil-trate. Reproduced with permission from Newton CW et al.258

Figure 11-19 One year after treatment of necrotic canal withRC2B, large granuloma and strands of proliferating epithelium areapparent. Reproduced with permission from Newton CW et al.258

Figure 11-20 Overfill with RC2B. After 1 year, severe inflamma-tion with necrosis is apparent. Adjacent bone was osteomyelitic.Reproduced with permission from Newton CW et al.258

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specifically cautioned dentists regarding severe post-operative complications that not infrequently accom-pany these [Sargenti] pastes when inadvertentlyextruded past the apex.”260

Endodontic overfillings are no surprise to anyonewho does root canal therapy. But, despite Sargenti’swarning to his followers not to overfill, 15% of the 806cases submitted for “Fellowship” status in the AmericanEndodontic Society demonstrated overfilling.261

Reaction to the physical and chemical trauma ofparaformaldehyde periradicularly can be so severe thatimmediate apical trephination is highly recommendedby the Sargenti proponents. For this exigency, the dentistis supplied with a “Fistulator” to trephine to the periapexto relieve the pressure and pain that might follow treat-ment with N2 (Figure 11-22). A survey conducted by theAmerican Endodontic Society of 48,134 cases treated by411 dentists shows 9,910 cases of trephination.148 Thisfigure indicates that the method was necessary 20.5% ofthe time when N2 or RC2B was used.

An even greater problem occurs when N2 or RC2B isforced into the maxillary sinus or the mandibularcanal. A number of cases of persisting paresthesia, pri-marily of the inferior alveolar nerve, have been report-ed following the misuse of paraformaldehydecements.262–268 That this accident can happen with anyroot canal sealer cannot be denied.269–273 However, asWeichman, a lawyer-endodontist, points out, paresthe-sia from other cements gradually fades away (J.Weichman, personal communication, June 2, 1982).Paresthesia from paraformaldehyde, on the other hand(since the nerve is literally embalmed), may remain for-ever (Figure 11-23). From Ankara, Turkey, a compara-tive study of the neurotoxic effects of sealers revealedthat formalin cements caused a faster and more pro-longed inhibitory effect on nerve transmission, as wellas paresthesia, than did other tested sealers.207

After reviewing the literature in 1988, Brodin notedthat more than 40 cases of neurotoxicity caused byoverfilling had been reported and that “sealers contain-ing formaldehyde were irreversible unless surgicaltreatment was performed (22 of 25 cases).”274 Sincethen, a number of cases involving N2, RC2B, SPAD,and Endomethasone have been reported.275–278

Obturation of the Radicular Space 595

Figure 11-21 Monkey study, periradicular area, 2 months after N2overfill (N2). Giant cells (GC) separating N2 from connective tissue(left) and lamellar bone (LB) (right). Reproduced with permissionfrom Hong YC et al.218

Figure 11-22 Perforation of maxillary incisor through incorrectuse of Fistulator. (Courtesy of Dr. Alfred L. Frank.)

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The tragedy of overfilling into the mandibular canal,especially with such toxic materials, relates to a mis-conception of the size of the pulp. Dentists spin moreand more material into the canal, far more than it takesto fill the space. Fanibunda points out that the averagepulp space of a maxillary central incisor is the size of adrop of water. This is the entire pulpal space, crownand root. The root canal is only a small portion of thisvolume. A mandibular molar pulp space would holdonly four drops, pulp chamber included.279 Enough isenough!

In summation, one might ask, “Why isn’t theSargenti method taught in American dentalschools?”280 and “Why does the Sargenti method raiseso many troublesome questions?”281 The answer toboth questions is rather simple. The Sargenti methodhas become a cult and, like most cults, is based more ontestimonials than on facts. The second reason, ofcourse, relates to the toxic components of the materialthat the cult insists are necessary to success.

These reasons, along with the countless lawsuits andout-of-court settlements centering around the tech-nique and cements, keep many from joining whilemany desert the ranks. Pitt-Ford reports the same turn-around in Britain. “N2 is now seldom used—probablybecause of the numerous reports of its adverse effectsand the fact that it is not recommended by dentalschools.”250

Sargenti himself indicated a double standard ofendodontic treatment when he publicly stated,“If I hadendodontic problems myself, and if I wished to have anexact endodontic treatment, I should certainly ask Dr.Herbert Schilder to treat me.”282

596 Endodontics

PREPARATION FOR OBTURATION

To this point, a good deal has been said about the mate-rials that go into the canal: their efficacy, their toxicity,their resorbability. But as the old adage goes, “Whatcomes out of the canal is much more important thanwhat goes into it.” For this reason, great emphasis hasbeen placed on radicular preparation and débride-ment—“biochemical preparation” à la Grossman or“cleaning and shaping” per Schilder.

Even if the canal space is perfectly débrided and isfree of all debris and bacteria, what of the dentin wallsleft? Are they free of bacteria? Are they prepared toadhere to the obturating material or will the sealantschemically adhere to them? One look at these so-called“glassy smooth” walls in an electron micrograph leavesone in doubt (Figure 11-24, A). The smear layer mayalso be loaded with bacteria that penetrate out of thelayer into the dentinal tubules (Figure 11-24, B).

The Dentin Interface

“Many of our currently accepted methods of chemo-mechanical preparation are inadequate in producing adebris-free canal.”283 In addition to the pulp tissuedebris and bacteria, several papers have described asludge or a “smeared layer” left attached to the innercanal walls, obstructing the dentinal tubules.283–289

Goldman and colleagues have demonstrated that thesmear layer, created by instrumentation, is primarilycalcific (inorganic) in nature.290

However, there is also an organic component,undoubtedly reflecting the chemical composition ofdentin: the greater inorganic and lesser organic com-ponent of the smear layer,291 as well as necrotic tissueand bacteria. Remember that the smear layer is subjectto early dissolution, and if apical leakage occurs, theloss of the smear layer will provide an easy ingress forfluid and bacteria.

There is no direct evidence that the smear layer mustbe removed. On the other hand, Yamada et al. state thata case can be made for its removal: “For instance, it mayinterfere with the adaptation of filling materials to thecanal wall by imposing an additional interface.”283 AtAristotle University in Greece, researchers reportedthat “smear layer removal resulted in a statistically sig-nificant reduction in microleakage when AH26 wasused as a sealer. However, the presence or absence ofthe smear layer had no significant effect on the sealingability of Roth 811.”292 In another vein, Yamada et al.went on to state, “In addition, opening all the tubulescan perhaps provide a better seal by allowing sealer orfilling material to penetrate” the dentin.283

Figure 11-23 Massive overextension of RC2B into inferior alveo-lar canal. Patient suffered permanent paresthesia. Lawsuit settledout of court against dentist and in favor of 26-year-old female sec-retary in Pennsylvania. (Courtesy of Edwin J. Zinman, DDS, JD)

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Gutmann, for example, has noted that thermoplasti-cized gutta-percha, and of course sealer, penetrates wellinto patent tubules freed of the smear layer.284 AnAthens research group also pointed out the importanceof using ethylenediaminetetraacetic acid (EDTA) toremove any calcium hydroxide clinging to the dentinwalls and thus blocking the tubuli.293

Opening the tubuli makes great sense. If chemicaladhesion between the dentin and sealers, pastes,cements, or plastics cannot be achieved, then why not amechanical lock? The material will flow or be forcedback into the empty dentin tubules, gripping like tenta-cles and forever resisting displacement (see Figure 11-12, B).

Opening the orifices of the dental tubules can beachieved with acids as shown by Loel,294 Tidmarsh,295

Waymen and colleagues,296 and Pashley and col-leagues,297 using various strengths of citric, phosphor-ic, or lactic acid (Figure 11-25), or by others usingEDTA as chelators.288,298–308 Calt and Serper, usingEDTA, also pointed out the importance of removingcalcium hydroxide dressing from the dentinal walls toopen the tubuli.309

More recently, workers at Tufts University foundthat “…the combined use of 10 cc of 17% EDTA(pH.7.5) followed by 10 cc of 5.25% sodium hypochlo-rite (NaOCl) produced the best overall results inremoving both superficial debris and the smeared

Obturation of the Radicular Space 597

Figure 11-24 A, Scanning electron micrograph view of dentin smear layer. Top half of photo is smear. Lower half of cut surface showsoccluded tubuli. B, Smear layer (left) after canal preparation. Note packed debris and extensions into tubuli. (Courtesy of Drs. MartinBrännström and James L. Gutmann.)

Figure 11-25 Scanning electron microscope view of smear layeretched away and tubuli opened by a 2-minute application of 37%phosphoric acid. A similar effect can be achieved in 5 to 15 seconds.(Courtesy of Dr. Martin Brännström.)

BA

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layer”283 (Figure 11-26). A group in Turkey achieved asimilar result using 17% EDTA combined with 5% eth-ylenediamine, an organic solvent.285 In arriving atthese conclusions, they had tested saline, citric acid(25%), and various combinations of sodium hypochlo-rite and EDTA. The chelator (EDTA) was very efficientin removing the inorganic (calcium salts) from thesmear layer all the way to the apical third. But the sodi-um hypochlorite was needed to dissolve and doucheaway the organic (dentin matrix, pulp remnants,necrotic and bacterial debris) constituents of thesmear. It goes without saying that sodium hypochloriteirrigation was used between instrument sizes duringcanal preparation.

Recent research reinforces the evidence that smearremoval is efficacious. One must bear in mindRawlinson’s findings, however, that 1 minute of ultra-sonic irrigation with citric acid and sodium hypochlo-rite did not remove all of the smear layer in the impor-tant apical third.127 The Minnesota group recommend-ed 3 minutes of irrigation, each with EDTA and sodi-um hypochlorite. This improved the bond withAH-26.302 The original group at Tufts used 10 cc eachof EDTA and sodium hypochlorite306,307 to improvethe bond with Bis GMA resin.126 Others reportedimproved bonding with ZOE, SealApex, AH-26,TubliSeal, and Diaket.302–309

With this final smear layer removal, the dentin inter-face needs only thorough drying to be ready to receivethe obturating materials.

METHODS OF OBTURATING THE ROOT CANAL SPACE

Over the years, countless ways and materials have beendeveloped to fill prepared canals. Again, Webster notedover 100 years ago, “…it would seem that the dentalprofession has not yet decided upon a universal rootcanal filling material.”228 At least today’s attempts seema bit more sophisticated than the “cotton, raw cotton,and cotton and gutta-percha,” noted by Webster. Onthe other hand, he favorably recommended warmgutta-percha and vertical compaction, but also notedthat warmed gutta-percha shrinks when it cools.228

Today, most root canals are being filled withgutta-percha and sealers. The methods vary by thedirection of the compaction (lateral or vertical) and/orthe temperature of the gutta-percha, either cold orwarm (plasticized).

These are the two basic procedures: lateral com-paction of cold gutta-percha or vertical compaction ofwarmed gutta-percha. Other methods are variations ofwarmed gutta-percha.

598 Endodontics

The methods are listed as follows:I. Solid Core Gutta-Percha with Sealants

A. Cold gutta-percha points1. Lateral compaction2. Variations of lateral compaction

B. Chemically plasticized cold gutta-percha1. Essential oils and solvents

a. Eucalyptolb. Chloroformc. Halothane

C. Canal-warmed gutta-percha1. Vertical compaction2. System B compaction3. Sectional compaction4. Lateral/vertical compaction

a. Endotec II5. Thermomechanical compaction

a. Microseal System, TLC, Engine-Plugger,and Maillefer Condenser

b. Hybrid Techniquec. J.S.-Quick-Filld. Ultrasonic plasticizing

D. Thermoplasticized gutta-percha1. Syringe insertion

a. Obturab. Inject-R-Fill, backfill

2. Solid-core carrier insertiona. Thermafil and Densfil,b. Soft Core and Three Dee GPc. Silver points

II. Apical-Third FillingA. Lightspeed Simplifill

Figure 11-26 Dentinal tubuli cleaned of smear layer and openedfollowing combined use of ethylenediaminetetraacetic acid andsodium hypochlorite. Reproduced with permission from YamadaRS et al.283

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B. Dentin-chipC. Calcium hydroxide

III. Injection or “Spiral” FillingA. CementsB. PastesC. PlasticsD. Calcium phosphate

The “compleat” clinician will master many, if not all,of these techniques. The rigidity of being “married” toone particular method or material limits not only caseacceptance but success as well.

Lateral Compaction of Cold Gutta-percha

The lateral compaction of cold gutta-percha points withsealer is the technique most commonly taught in dentalschools and used by practitioners and has long been thestandard against which other methods of canal obtura-tion have been judged. This technique encompasses firstplacing a sealer lining in the canal, followed by a meas-ured primary point, that in turn is compacted laterallyby a plugger-like tapering spreader used with verticalpressure, to make room for additional accessory points(Figure 11-27). The final mass of points is severed at thecanal’s coronal orifice with a hot instrument, and finalvertical compaction is done with a large plugger. If exe-cuted correctly, solid canal obturation will totally reflectthe shape and diversions of the properly prepared canalnetwork (Figure 11-28).

Lateral condensation can only be achieved if certaincriteria are fulfilled in canal preparation and instru-ment selection. The final canal shape should be a con-tinuous taper, approaching parallel in the apical area,that matches the taper of the spreader/plugger. The

Obturation of the Radicular Space 599

Figure 11-27 ISO standardized spreaders and matchinggutta-percha points. A, Size #25 hand spreader and matchinggutta-percha point. B, Size #25 finger spreader and matchinggutta-percha point. Instruments and points are color-coded thesame. (Spreaders courtesy of Dentsply/Maillefer Co. Points cour-tesy of Coltene Whaledent/Hygenic Co.)

Figure 11-28 Complete root canal obliteration using multiplepoint technique. Notice density of gutta-percha mass. Filling con-forms exactly to size and shape of last endodontic instrument used.

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spreader must reach within 1.0 to 2.0 mm of the work-ing length (Figure 11-29), an apical stop must be creat-ed to resist apically directed condensation, and theaccessory gutta-percha cones must be smaller in diam-eter than the spreader/plugger (see Figure 11-27).Lateral condensation is not the technique of choice inpreparations that cannot meet these criteria and not allcanals can be shaped to meet these criteria. Beforeembarking on the filling process, however, severalimportant steps in preparation must first be complet-ed: spreader size determination, primary point andaccessory point size determination, drying the canal,and mixing and placement of the sealer.

Spreader Size Determination. Before trying in thetrial point, it is mandatory to fit the spreader to reachto within 1.0 to 2.0 mm of the true working length andto match the taper of the preparation. Spreaders areavailable that have been numbered to match the instru-ment size (Figure 11-30). Therefore, a spreader of thesame apical instrument size or one size larger is chosenso that it reaches to within 1.0 to 2.0 mm but will notpenetrate the apical orifice. Not all canals can beshaped to fit the variety of lengths and tapers of avail-

600 Endodontics

able spreaders. This technique requires a knowledgeand understanding of the size and shapes created bydifferent cleaning and shaping instruments, as well asof the spreaders. If the spreader taper is greater than thecanal taper, there will be an apically directed force dur-ing condensation that can result in overfill. If the taperof the canal is greater than that of the spreader, there isa tendency to displace the master cone coronally duringcondensation.

Allison and his colleagues at the University ofGeorgia vividly demonstrated the importance of deepspreader penetration. They also pointed out that “themost important factor affecting the quality of the api-cal seal is the shape of the canal,” a true tapered prepa-ration that would allow the spreader to nearly reach theapical terminus. Canals so treated had virtually no api-cal percolation310 (Figure 11-31). Spreaders shouldalways be fit into an empty canal (Figure 11-32) toensure that the force is absorbed by the gutta-perchaand not the canal walls, which could result in root frac-ture. After the gutta-percha is placed, and the spreaderis inserted but does not reach the premeasured depth,condensation of the gutta-percha will occur laterally

Figure 11-29 Microleakage into obturated canals related to flareof cavity preparation and depth of spreader penetration. Left, Finaldepth of spreader, A, is 5 mm short of prepared length of canal.Radioisotope leakage is 4.8 mm (between arrows) into canal.Right, Canal with flared preparation allows spreader depth towithin 1 mm of primary point length. Radioisotope leakage(between arrows) only 0.8 mm into canal. Reproduced with per-mission from Allison DA et al.310

Figure 11-30 Luks finger pluggers are available in four differentsizes and two lengths. The apical diameter is the same for all—alittle less than 0.20 mm—and they vary in increasing diameters oftheir taper. (Courtesy of Dr. Carl W. Newton.)

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from a force directed from the canal walls toward thegutta-percha.

A rubber stop should be placed on the shaft of thespreader to mark true working length minus 1 mm. Itis then set aside for immediate use.

Primary Point Size Determination. Gutta-perchapoints have been standardized in size and shape to matchthe standardized instrument sizes. They have even beencolor-coded to match the instrument’s color.

Conventional sized cones are too tapered with a bulk ofmaterial in the coronal area that would resist penetrationof the spreader. However, nothing should be left tochance; the primary point should be selected to matchthe size of the last instrument used at the apex and shouldbe tested in place and confirmed radiographically.

Gutta-percha comes sterilized from the package or itmay be sterilized with a germicide for 5 minutes insodium hypochlorite (5.25%), hydrogen peroxide(3%), or chlorhexidine (2%).311,313 Gutta-percha itselfdoes not readily support bacterial growth.313

The four methods used to determine the proper fit ofthe primary point are as follows: (1) visual test, (2) tac-tile test, (3) patient response, and (4) radiographic test.

Visual Test. To test the point visually, it should bemeasured and grasped with cotton pliers at a positionwithin 1 mm short of the prepared length of the canal.The point is then carried into the canal until the cottonpliers touch the external reference point of the tooth.This master point should always be tried in a wet canalto simulate the lubrication of the sealer. If the workinglength of the tooth is correct and the point goes com-pletely to position, the visual test has been passedunless the point can be pushed beyond this position.This can be determined by grasping 1 mm farther backon the point and attempting to push it apically. If thepoint can be pushed to the root end, it might well bepushed beyond into the tissue. Either the foramen wasoriginally large or it has been perforated. If the pointcan be extended beyond the apex, the next larger sizepoint should be tried. If this larger point does not gointo place, the original point may be used by cuttingpieces off the tip. Each time the tip is cut back 1 mm,the diameter becomes larger by approximately .02 mm.By trial and error, the point is retried in the canal untilit goes to the correct position.

Jacobsen has shown the distortion in the point thatensues if scissors are used to “snip” off the tip. He showsthat distortion can be avoided by “rolling the pointback and forth on a sterile glass plate and applying gen-tle pressure with a No. 15 scalpel blade”314 (Figure 11-33). The main reason for trial point testing is to be surethe point extends far enough for total obturation butwill not extend beyond the apical foramen. The termi-nation of the point within 1 mm short of the preparedlength provides for apical movement from the verticalforces of compaction aided by lubrication from thesealant. One cannot predictably rely on the spreader toseat the master point if it has not been confirmed to thedesired position. If everything is right, the solid-corematerial is sealed exactly into the prepared space, notpushed beyond into an overfill.

Obturation of the Radicular Space 601

Figure 11-31 Prepared root canal obturated by lateral condensa-tion of gutta-percha and sealer. Note extension of gutta-percha intodepression in canal (arrow). (Courtesy of Dr. J. H. Gutiérrez and Dr.C. Gigoux, Concepcion, Chile.)

Figure 11-32 The Luks plugger is premeasured and placed in theempty canal to verify penetration into the apical 1.0 to 2.0 mm.Condensation at this depth can be achieved with the assurance thatthe gutta-percha will absorb the pressure and not the canal walls.(Courtesy of Dr. Carl W. Newton.)

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Tactile Test. The second method of testing the trialpoint is by tactile sensation and will determine whetherthe point tightly fits the canal. In the event the apical 3to 4 mm of the canal have been prepared with near par-allel walls (in contrast to a continuous taper), somedegree of force should be required to seat the point, and,once it is in position, a pulling force should be requiredto dislodge it. This is known as “tugback.” Allison andthe Georgia group have shown, however, that significanttugback in primary gutta-percha point placement is notessential to ensure a proper root canal seal.315

Again, if the point is loose in the canal, the next larg-er size point should be tried, or the method of cuttingsegments from the tip of the initial point, followed bytrial and error positioning, should be used. Care mustbe taken not to force the sharp tip of a point throughthe foramen.

Patient Response. Patients who are not anes-thetized during the treatment of a nonvital pulp or atthe second appointment of a vital pulp may feel thegutta-percha penetrate the foramen. Adjustments canthen be made until it is completely comfortable. This isa good test when the position of the foramen does notappear to be accurately determined by the radiographor by tactile sensation. Pulp remnants from a shortpreparation will cause a sensation of much greaterintensity than periapical tissue. Granulation tissue maynot produce any sensation at all.

Radiograph Test. After the visual and tactile tests forthe trial point have been completed, its position must bechecked by the final test—the radiograph (Figure 11-34).The film must show the point extending to within 1 mmfrom the tip of the preparation. Radiographic adaptation

602 Endodontics

is a better criterion of success than either the visual or tac-tile method.315

The trial point radiograph presents the final oppor-tunity to check all of the operative steps of therapycompleted to date. It will show whether the workinglength of the tooth was correct, whether instrumenta-tion followed the curve of the canal, and whether a per-foration developed. It will also, of course, show the rela-tionship of the initial filling point to the preparation.

Occasionally the radiograph shows the point forcedwell beyond the apex. If this is the case, an incorrectworking length has been used during instrumentation,and the operator may have wondered why the patientcomplained of discomfort. The overextended point

Figure 11-33 Length-adjusted gutta-percha points. A, Size 30 gutta-percha point shortened with scissors. Distortion prevents proper place-ment at apical seal. B, Size 30 gutta-percha point trimmed with scalpel, allowing more perfect apical fit. Reproduced with permission fromJacobsen EL.314

Figure 11-34 Trial point radiograph. Confirmation film indicatesthe primary point should be advanced by another 2.0 mm by eitherenlarging one more size or trying the next smaller point. (Courtesyof Dr. Carl W. Newton.)

A B

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should always be shortened from the fine end and thencarefully returned to proper position. It should neverbe just pulled back to a new working length, in whichcase it would be loose in the canal. In this new position,it should again pass the tactile and radiographic tests oftrial points. It should never be manipulated so that itjust appears to fit in the film. It must fit tightly andcome to a dead stop.

Sometimes the initial point will not go completelyinto place even though it is the same number as the lastenlarging instrument. This condition may arise because(1) the enlarging instrument was not used to its fullestextent, (2) there was a larger than standard deviationbetween the sizes of instruments and gutta-percha, (3)debris remains or was dislodged into the canal, or (4) aledge exists in the canal on which the point is catching.

In any case, the problem can be solved by one of twomethods: selecting a new file of the same number andre-instrumenting the canal to full working length untilthe file is loose in the canal, or selecting a smaller sizegutta-percha point. Trial and error will determinewhen the point is seated. If a ledge has been developedin the canal wall, it must be removed by the methodsuggested in chapter 10.

Preparation of the Initial Point. After the initialpoint has passed the trial point tests, it should beremoved with cotton pliers that scar the soft point orsnipped with the scissors at the reference point(Figure 11-35).

Drying the Canal. While preparations are beingmade to cement the filling point, an absorbent paperpoint should be placed in the canal to absorb moistureor blood that might accumulate. Larger paper pointsare followed by smaller paper points until full length isachieved. To determine the presence of moisture in thecanal, one must remove the absorbent point and drawthe tip along the surface of the rubber dam. If the pointis moist, it will leave a mark as it removes the powderfrom the dam. When this procedure has been repeatedwith fresh points that no longer streak the dam, thefinal paper point is left in place to be removed just asthe sealer is to be introduced. Any bleeding should bestopped, the blood irrigated from the canal, and caretaken to avoid penetrating beyond the apex with thefinal paper point. Excess moisture or blood may affectthe properties of the sealer, although fluids may becompletely displaced during condensation and notaffect the seal.316

Mixing and Placement of the Sealer. Mixing. Asterile slab and spatula are removed from the instru-ment case or are sterilized by wiping with a gauzesponge soaked in germicide and dried with a sterile

sponge. One or two drops of liquid are used and thecement is mixed according to the manufacturer’s direc-tions. The cement should be creamy in consistency butquite heavy, and should string out at least an inch whenthe spatula is lifted from the mix (Figure 11-36).

Benatti and colleagues tested five commerciallyavailable sealers and concluded that ideal consistency isachieved when the mixture can be held for 10 secondson an inverted spatula without dropping off and willstretch between the slab and spatula 2 cm before break-ing. Ideal consistency permits ample clinical workingtime and minimal dimensional change.317

Sealer should not be mixed too thin, but on theother hand, it must not be so viscous that it will notflow between the gutta-percha points or penetrateaccessory and lateral canals or the dentin tubules.318

Placement. Sealer can be place in abundance toensure thorough canal wall contact because the tech-

Obturation of the Radicular Space 603

Figure 11-35 A, Removal of measured and tested initialgutta-percha point. Cotton pliers mark gutta-percha at incisal edge.B, Standardized points are seated at the working length andtrimmed at the occlusal reference point with scissors. The masterpoints should reach to within 1.0 mm of the working length.(Courtesy of Dr. Carl W. Newton.)

A

B

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604 Endodontics

nique will displace all excess sealer coronally. Rootcanal cement/sealer may be placed in a number ofways. Some clinicians “pump” the sealer into the canalwith a gutta-percha point. Some carry it in on a file orreamer, which is twirled counterclockwise, pumped upand down, and wiped against all the walls. Some userotary or spiral paste fillers turned clockwise in one’sfingers or very slowly in a handpiece (Figure 11-37).

Using rotary or spiral paste fillers is not withoutdanger. If powered by a handpiece, they can be easilylocked in the canal and snapped off (Figure 11-38).Twirling them in the fingers is safer, and Lentulo spiralsare now being made with regular instrument handles(Dentsply/Maillefer; Tulsa, Okla. and Switzerland).

Another problem encountered in using rotary-pow-ered Lentulo spirals comes from “whipping up” thecement in the canal and causing it to set prematurely.The primary point will then not go into place.Investigators in Scotland also found that the poweredLentulo spiral consistently caused sealer extrusion.319

A more recent method is to place the cement with anultrasonic file—run without fluid coolant, of course.319

A US Army group found ultrasonic endodontic sealerplacement significantly superior (p = .001) to handreamer placement. They were pleased to see propercoverage to the apical orifice but not beyond. Lateraland accessory canals were filled as well. As with theLentulo spiral-placement, they found that ZOE cementset within a few seconds when ultrasonically spatulatedin the canal. Heat generated by ultrasonics can acceler-

Figure 11-36 Root canal cement should be mixed to thick, creamyconsistency, which may be strung off slab for 1 inch.

Figure 11-37 Rotary paste fillers made for contra-angle handpiececan also be rotated clockwise by finger action. Used for placing ini-tial sealer with solid core root fillings or completely filling the canalwith paste filling. A, Produits Dentaires, Switzerland. B, MicroMega, France. C, Hawes-Neos, Switzerland. The Hawes-Neos type ispreferred because of its stronger rectangular blade. (Courtesy of Dr.Frederick Harty, London.)

Figure 11-38 Lentulo spiral fractured in distal canal of lowermolar. Careful observation reveals spiral also fractured in mesialcanal and a cervical perforation and a broken reamer in mesial gin-giva. (Retouched for clarity.)

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ate ZOE sealers. However, they used AH-26 successful-ly.320,321 A San Antonio group also found the Lentulo tobe the most efficient in coating the walls: 90.2%, com-pared with using a K-file at 76.4% or using a gutta-per-cha point at 56.4%. They suggested that complete cov-erage may not be possible.322

Placement of the Master Point. The premeasuredprimary (or master, or initial) point is now coated withcement (Figure 11-39) and slowly moved to full work-ing length. The sealer acts as a lubricant. The patientmay experience some minor discomfort from this pro-cedure as air or sealer is evacuated from the canalthrough the foramen. If the resistance form has beencorrectly prepared so that a “minimal opening” exists atthe foramen, no more than, and usually not as much as,a tiny puff of cement will be forced from the apex.

It is frequently asked why the well-fitting initialpoint does not force a great quantity of cement throughthe apical foramen. The answer lies in the taperedshape of the point and corresponding shape of thecanal. One should not think of the point as a plunger,for a plunger has straight walls. The tapered point doesnot actually touch the walls of the prepared canal untiljust that moment when it reaches its final seat. It willthus not force quantities of cement ahead of it, but willrather displace cement coronally as it is slowly movedinto position. Thus one need not fear that there is anexcessive amount of cement in the canal prior to place-ment of the point.

Multiple-Point Obturation with Lateral Compaction

When the fit of the cemented primary point is ensured(Figure 11-40, A), the butt end, extending into thecoronal cavity, should be removed with a hot instru-ment or scissors to allow room for visualization and thespreader that is to follow.

The premeasured spreader is then introduced intothe canal alongside the primary point, and with arotary vertical motion is slowly moved apically to fullpenetration, marked on the shaft with a silicone stop.(Figure 11-40, B). It is the wedging force that occursbetween the canal walls toward the gutta-percha thatresults in deformation and molding of the gutta-perchato the opposite canal walls (Figure 11-41). There is noneed to apply a lateral force to the spreader. Weine rec-ommends that the initial spreader be left in place a fullminute to allow the primary gutta-percha time toreconform to this pressure.323 One must know that,along with the lateral force of spreading, a verticalforce, albeit less, is also exerted.315,324 If the spreaderdoes not reach the premeasured length within the api-cal 1 mm, firm apical pressure can be applied with the

knowledge that the gutta-percha, and not the tooth, isabsorbing the force that could result in fracture (Figure11-42). If full penetration is still not achieved, a spread-er that is a size smaller can be used, which will bind api-cally to the previous spreader. The master point mayappear to elongate slightly coronally as it stretches toplasticity at the point of condensation. Remember, ade-quate condensation does not occur unless the initialspreader reaches length.

The spreader is then removed with the same recip-rocating motion and is immediately followed by thefirst auxiliary point inserted to the full depth of thespace left by the spreader (Figure 11-40, C). Selectingauxiliary cones that are the same size or smaller indiameter or taper than the spreader requires a knowl-edge of ISO Standards for conventional gutta-perchacones and manufacturer’s specifications for the chosenspreaders. Spreader penetration that is limited by abulk of gutta-percha in the midroot area does notresult in adequate condensation in the important api-cal area. Some clinicians use heat at this point to softenthe bulk of gutta-percha and allow easier penetrationthrough the coronal area. This point is followed bymore spreading (Figure 11-40, D) and more points(Figure 11-40, E), more spreading and more points,until the entire root cavity is filled.

To ensure a cohesive filling, additional sealer shouldbe added with each point as a lubricant to facilitate fullpenetration. Obturation is considered complete whenthe spreader can no longer penetrate the filling massbeyond the cervical line.

At this time the protruding points are severed at theorifice of the canal with a hot instrument (Figure 11-40, F). Vertical compaction with a large plugger willthen ensure the tightest possible compression of the

Obturation of the Radicular Space 605

Figure 11-39 Primary point (arrow) coated with cement. Sealermay be used in abundance to ensure thorough coating since excesssealer will be displaced coronally in a properly shaped canal.(Courtesy of Dr. Carl W. Newton.)

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gutta-percha mass and provide a more effective sealagainst coronal leakage.325 All of the sealer and gutta-percha should then be removed from the pulp chamberand a final radiograph taken (Figure 11-43). After anintraorifice barrier is placed, either a final or temporarycoronal filling should follow.

If one follows this technique—lateral compaction ofcold gutta-percha points—a number of questions mayarise: What size and style of spreader should be used?Which accessory gutta-percha points match thespreaders in size and taper? How much force should beused with a spreader? Can vertical fractures occur?

Spreader Size and Taper. Spreaders are supplied inmultiple shapes, sizes, lengths, and tapers, includinghand spreaders with a bent binangle shaft, and small

606 Endodontics

straight finger spreaders. Nickel titanium has alsoimproved flexibility and has been shown to penetrateto significantly greater depths than does stainless steelin curved canals.326

In 1955 Ingle drew attention to the discrepancy inspreader sizes as well as matching gutta-percha points.327

After 35 years of confusion, the ISO/ADA endodonticstandardization committee, in 1990, recommended thatspreaders and pluggers be modeled after the acceptedstandardized instruments and gutta-percha points, No.15-45 for spreaders and No. 15-140 for pluggers.

This new attempt to bring order out of chaos wouldabandon the old confusing numbering systems (1-10,D-11, D-11T, ABCD, XF, FF, MF, F, FM, M, etc) and rec-ommend that all spreaders, pluggers, and auxiliary

Figure 11-40 Lateral compaction, multiple-point filling procedure. Spreader has previously been tested to reach to within 1.0 mm of api-cal constriction. Thin layer of sealer lines canal walls, tip of point is coated with cement. A, Primary point is carried fully to place, to within1.0 mm of “apical stop.’’ Excess in crown is severed at cervical with hot instrument. B, Spreader (arrow) is inserted to full depth, allowed toremain 1 full minute as gutta-percha is compacted laterally and somewhat apically. C, Spreader is removed by rotation and immediatelyreplaced by first auxiliary point previously dipped in sealer. D, Spreader (arrow) is returned to canal to laterally compact mass of filling.Secondary vertical compaction seals apical foramen. E, Spreader is again removed, followed by matching auxiliary point. Process continuesuntil canal is totally obturated. F, All excess gutta-percha and sealer are removed from crown to below free gingival level. Vertical compactioncompletes root filling. After an intraorifice barrier is placed, a permanent restoration with adhesives is placed in crown.

A B C

D E F

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gutta-percha points meet the ISO/ADA specification.More recent developments in non-ISO/ADA specifica-tion for the variable taper (.04/.06 taper instruments)will require more understanding of the final dimen-sions of the preparation for spreader selection. Rotaryinstrumentation with these instruments offers the pos-sibility of a very standardized preparation with knowndiameter and taper at every level of the canal.

A number of investigations that attempted to untan-gle the problem would become moot if standardizationwent into effect.328–331 In 1991, Hartwell and his asso-ciates331 forwarded the same opinion regarding stan-dardization that was voiced by Ingle 36 years before.327

In keeping with the trend toward standardization,Martin has introduced a set of calibrated hand spread-ers and pluggers to match in size and taper theISO/ADA instrument standardization. The instru-ments, with color-coded handles, range in size fromNo. 20 through No. 60 M Series (Figure 11-44)(Dentsply/Maillefer; Tulsa, Okla.). The space made bythese spreaders may be filled with gutta-percha points(again color-coded) of the same number.

Stress and Fractures from Lateral Compaction.Hatton and his associates found they could adequatelyseal root canals with as little as 1 kg of spreader pres-sure. They applied up to 2.5 kg and suggested thatexcessive forces could produce fractures.332 The Iowagroup found 3 kg to be the average lateral condensationpressure exerted by six endodontists. Although theyfound the incidence of immediate vertical root frac-tures to be low at 3 kg, they speculated that a buildupof root distortion, “stored” in the root, could well bereleased later as a fracture. They produced more frac-

Obturation of the Radicular Space 607

Figure 11-41 SEM cross-sections of lateral compaction illustrateshow the gutta-percha is condensed in the apical area with the place-ment of the initial spreader. Note how all the spreader tracts occurfrom the canal wall into the gutta-percha in a “wedging” fashionand adapt the gutta-percha to the opposite walls. (Courtesy of Dr.Carl W. Newton.)

Figure 11-42 Root fracture occurs when the wedging force isabsorbed by the canal walls. Premeasuring the spreader depth canreduce risk of fracture. (Courtesy of Dr. Carl W. Newton.)

Figure 11-43 Final compaction of three canals reflects properpreparation, premeasured spreader depth, full adaptation of pri-mary point, and careful addition of accessory points. (Courtesy ofDr. Carl W. Newton.)

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tures with the D-11 hand spreader than with the lesstapered B-finger spreader.333

At Melbourne University researchers compared loadand strain using hand versus finger spreaders andfound “that strains generated by finger spreaders weresignificantly lower than hand spreaders.” They alsoconcurred with the Iowa group when they noted thatlateral condensation may lead to incomplete root frac-tures and that these fractures may later lead to full ver-tical fractures under the stresses of restoration or mas-tication.334 Blum described the intracanal pressuredeveloped during condensation as the “wedging effect”and measurements graphed from a force analyzerdevice showed that gutta-percha deformation occurs atonly 0.8 kg for lateral condensation.335

Researchers at the University of Washington found ittook 7.2 kg (15.8 lbs) to fracture a maxillary central inci-sor. However, 16% of their maxillary anterior teeth frac-tured at loads under 10 kg. They felt that 5 kg (11 lbs)were a “safe load” for these husky teeth.336 When thissame group tested mandibular incisors, they producedfractures with only 1.5 kg (3.3 lbs) of load, and 22% of

608 Endodontics

their lower incisors fractured at loads less than 5 kg, inmarked contrast to the maxillary incisors and canines. Inthe lower incisor sample, fractures occurred when onlythree accessory points were compacted. Like the Iowa andMelbourne groups, they speculated that “vertical rootfractures might not be detected clinically until long afterthe fracture was initiated.”337 Again at Iowa, the relation-ship between tooth reduction and vertical fracture wasstudied to show that vertical root fracture did not occurin maxillary anterior teeth under a constant force of 3.3kg for 15 seconds until 40% of the total canal width wasreduced and was always preceded by visible craze lines.338

From Greece, Morfis condemned lateral condensa-tion and long post placement as responsible for rootfractures. He reported 17 (3.69%) vertical fractures of480 endodontically treated teeth.339

Using engineering models, a US Air Force groupfound that “lateral condensation required a smalleramount of force than vertical condensation to producethe same amount of stress near the apex…” whereas“the average stress throughout the entire canal washigher for vertical condensation.…” They felt that the

Figure 11-44 A, Standardized, double-ended, spreader/plug-gers, sized and color coded to match ISO instrument sizes. B,Spreader—note sharp point. C, Plugger—note blunted point.(Courtesy of Dentsply/Maillefer-M-Series.)

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“term lateral condensation may be somewhat of a mis-nomer,” and that “lateral condensation may be morelikely to produce undesirable stress concentrationsthan is vertical condensation.”340 This was noted earli-er at the University of Georgia, when it was stated that“the force of the spreader is apparently transmitted 1 to2 mm beyond the spreader tip and molds the pointsand sealer against the walls as it forces them apical-ly.”315 Essentially the same thing was noted at theUniversity of North Carolina.341

Nickel-Titanium Spreaders

Studying the distribution of forces in lateral condensa-tion, a US Army group used photoelastic models todemonstrate that nickel-titanium spreaders inducedstress patterns distributed along the surface of curvedcanals compared to concentrated spikes of stress whenstainless steel spreaders were used.342 They also point-ed out that, because of their flexibility, nickel-titanium“spreaders penetrated to a significantly greater depththan the stainless steel spreaders in curved canals.”343

Variations of Lateral Compaction. The precedingillustration of obturating a straight canal by lateralcompaction applies with modifications for fillingcurved canals, immature open apices, or tubular canals.

Curved Canals. Virtually all canals exhibit somecurvature. Over 40% of maxillary lateral incisors havea “breaking curve” in the apical third. Over 50% of thepalatal roots of maxillary first molars curve back to thebuccal. These are examples of the apical curves.General root curvature is apparent radiographically inmost of the posterior teeth. Many “hidden” curves tothe buccal or lingual cannot be seen radiographically inanterior teeth.

Lateral compaction of curved canals can be veryeffective in most cases. However, it may be difficult ifnot impossible in severely curved, dilacerated, or bayo-net canals. If smaller, more flexible spreaders cannotreach within the apical 1 mm, or the taper of the prepa-ration is less than that of the spreader, then lateral con-densation is not the technique of choice. Teasing a flex-ible primary point smaller than size 30 to place at theapex, or expecting a stiff spreader to reach within 1 mmof the working length precludes the use of proper later-al compaction. There are other techniques that usewarmed or thermoplasticized gutta-percha that aremore applicable. They will be discussed subsequently.

In the vast majority of curved canals, where lateralcompaction is applicable, the routine is exactly thesame: sealer placement and primary point placement,followed by spreaders and auxiliary points. Alternatingspreader sizes is usually required to reach the premea-

sured depth in narrowly prepared canals. One mustknow, however, that more vertical force will be exertedagainst the primary point as the spreader will tend tocatch in the gutta-percha and force it apically (Figure11-45). Overfills occur with greater frequency when thevertical force is greater. This also occurs when thespreader taper is greater than the canal preparation.Nickel-titanium spreaders will penetrate to greaterdepths and distribute forces more evenly than will stain-less steel spreaders in curved canals (Figure 11-46).

Immature Canals and Apices. The immature canalis complicated by a gaping foramen. The apical open-ing is either a nonconstrictive terminus of a tubularcanal or a flaring foramen of a “blunderbuss” shape.

Every effort should be made to attain the geneticallyprogrammed closure of the foramen that remains openbecause of early pulp death. This can be accomplished byapexification, a method of recharging the growth poten-tial and restoring root growth and foramen closure.Apexification is discussed thoroughly in chapter 15.

If apexification fails or is inappropriate, specialmethods must be used to obturate the canals withoutbenefit of the constrictive foramen serving as a confin-ing matrix against which to condense. Fortunately, in

Obturation of the Radicular Space 609

Figure 11-45 Lateral compaction of primary gutta-percha pointin curved canal. Spreader catches into point, forcing it apically.Extra vertical compaction must be compensated for.

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most of these cases, pulps of straight-root maxillaryincisors have been devitalized by impact trauma. Inother cases, the foramen has been either trephined toallow for abscess drainage or destroyed by the erosionof external root resorption. Occasionally an immaturefirst molar with pulp necrosis from early caries is a can-didate. In either case, calcium hydroxide apexificationshould be first tried.

Complete obturation requires the use of the largestgutta-percha points customized (“tailor made”) to fitthe irregular apical stop or barrier. Lateral compactionis not the technique of choice because the resistance ofthe canal walls for lateral pressure is reduced in imma-ture teeth and the greater bulk of gutta-percha requiresan even greater force to deform. Remember that com-paction occurs from the canal wall into the mass ofgutta-percha. Gutta-percha, in seldom-used sizes, canbecome brittle in storage and requires even greaterpressure to deform. Warm gutta-percha techniques arebest suited for filling immature canals and apices.

610 Endodontics

Tubular Canals. The large tubular canal with littleconstriction at the foramen may best be filled with a“coarse” primary gutta-percha cone that has beenblunted by cutting off the tip. Sometimes the canal issuch that a large “tailor-made” point must be used. Ineither case, the “trial point” should pass the tests ofproper fit.

The objective of the primary point is to block theforamen, insofar as possible, while auxiliary points arecondensed to complete the filling (Figure 11-47). Thelength of tooth must be marked on the spreader so thatit will not be forced out the apex. With care, a well-compacted filling may be placed without gross overfill-ing of either cement or gutta-percha. Warm gutta-per-cha techniques should be considered in larger canalsafter the apical seal has been achieved by customizingor lateral compaction.

Tailor-Made Gutta-Percha Roll. If the tubular canalis so large that the largest gutta-percha point is stillloose in the canal, a tailor-made point must be used asa primary point. This point may be prepared by heat-ing a number of large gutta-percha cones and combin-ing them, butt to tip, until a roll has been developedmuch the size and shape of the canal (Figure 11-48).

Figure 11-46 Note the difference in ability of same-size spreadersto reach to within 1.0 mm of working length in a curved canal. A,Stainless spreader 2.0 mm shy of goal. B, Nickel-titanium spreaderreaches fully to apical stop. (Courtesy of Dr. Carl W. Newton.)

A

B

Figure 11-47 A, Cross-section of tubular canal in “young” tooth,ovoid in shape. B, Blunted, “coarse’’ gutta-percha cone ortailor-made cone used as primary point, followed by spreading andadditional points to totally obturate ovoid space. Final vertical com-paction with large plugger.

A

B

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The roll must be chilled with a spray of ethyl chlorideor ice water to stiffen the gutta-percha before it is fittedin the canal. If it goes to full depth easily but is tooloose, more gutta-percha must be added. If it is onlyslightly too large, the outside of the gutta-percha can beflash-heated over the flame and the roll forced to prop-er position. By this method, an impression of the canalis secured (Figure 11-49).

The outer surface of the stiffened point may also besoftened by heat or “flash’’-dipping the point in chloro-form, eucalyptol, or halothane (Figure 11-50, A). Byrepeating this exercise, one can essentially take an

Obturation of the Radicular Space 611

Figure 11-48 Preparation of “tailor-made” gutta-percha roll. A,Number of heated, coarse, gutta-percha points are arranged butt totip, butt to tip on sterile glass slab. B, Points are rolled with spatula intorod-shaped mass. C, By repeated heating and rolling, the roll ofgutta-percha is formed to approximate size of canal to be filled. Novoids should exist in mass. D, Before trial point testing of tailor-maderoll, gutta-percha should be chilled with ethyl chloride spray.

Figure 11-49 Trial point radiograph of tailor-made gutta-perchapoint. Space exists alongside this roll, which indicates it should beenlarged and retested.

Figure 11-50 Chloroform dip technique. A, Note that just the tip isimmersed and for only 1 second. B, Final compaction of tubularcanal. Warm gutta-percha/vertical compaction is preferred techniquefor cases with such thin walls. (Courtesy of Dr. Carl W. Newton.)

A

B

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internal impression of the canal. A mark is made on thebuccal surface of the cone and it is dipped in alcohol tostop the action of this solvent. Alcohol can also be usedto assist in drying the canal prior to filling. Someshrinkage may alter the final impression and any com-paction before the solvent has evaporated will permitthe point to continue to flow under pressure.

Simpson and Natkin have suggested a specializedfilling technique for those teeth with tubular canalsbut closed apices.344 These are the roots that wereoriginally blunderbuss in shape but have beeninduced to complete their growth by the introductioninto the root canal of a biologically active chemical,such as calcium hydroxide.

Efficacy of Lateral Compaction. As previouslystated, lateral compaction of gutta-percha with sealer isthe obturation technique against which other tech-niques are measured. In some cases, it has been provedbetter than other methods.345–351 In other reports, itwas found to be as effective as other techniques.352–370

But in other citings, it proved not as adequate.371–380

Weine, a longtime advocate of lateral compaction,and his associates have shown that lateral compaction,done correctly, provides an optimum obturation of theentire canal.323 The Loyola research was prompted bySchilder’s characterization of lateral compaction asineffective, that “…gutta-percha cones never mergeinto a homogeneous mass, but they slip and glide andare frozen in a sea of cement”381 (Figure 11-51).

The Weine group enlarged curved canals in plasticblocks to size 30 apically and flared to size 45 coronal-ly. They then cemented into place a pink No. 30 gutta-percha point and followed it with a No. A finger plug-ger (with a rounded tip) used as a spreader. Each No. 20auxiliary gutta-percha point that followed was special-ly colored a different color.

As Figure 11-52 shows, the primary and accessorypoints more than adequately fill the canal and illustratehow the spreader uses the wall opposite to provide thecompressive force of the gutta-percha against theopposite canal wall. And far from “being frozen in a seaof cement,” the points dominate the space with onlytwo small flashes of cement showing.382

The Indiana research group also showed the efficacyof lateral compaction as well as the paramount impor-tance of thoroughly débriding the canal.345 Fifteen daysfollowing obturation, they found healing already underway. After 45 days, only slight inflammation remained.At the end of 1 year, even though one canal was over-filled (Figure 11-53, A), the tissue was remarkedlyhealthy. In marked contrast, a poorly filled canal exhib-ited chronic apical periodontitis at 75 days (Figure 11-

612 Endodontics

53, B). All of the unfilled control teeth suffered severeperiradicular lesions.345

One must conclude that the objectives of root canaltherapy are well met by total canal débridement andobturation by lateral compaction. Failures will be dueto neglect of these objectives plus overzealous com-paction leading to fracture.

Chemically Plasticized Cold Gutta-percha. A mod-ification of the lateral compaction technique involves

Figure 11-51 Top, Schilder’s concept of obturation by lateralcompaction. A, “Cross-section of middle third of root demonstrat-ing primary and auxiliary cones. Gutta-percha cones frozen in a seaof cement.” B, “Gutta-percha cones never merge into homogeneousmass.” Bottom, Example of truly inadequate lateral compactioncaused by paucity of sealer and poor spreading. Top reproducedwith permission from Schilder H.381 (Bottom courtesy of Dr. CarlW. Newton.)

B

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Obturation of the Radicular Space 613

Figure 11-52 Cross-sections of an in vitro study, demonstrating the efficacy of lateral compaction of cold gutta-percha points, each pointa different color. A, Single primary point 1.0 mm from apex apparently fills canal. B, First auxiliary point added following distortion of mas-ter point, 2.0 mm from apex. C, Second and third auxiliary points 3.0 mm from apex. Canal still totally obturated. D, Second, third, andfourth points fill canal. Primary point not visible. Small amount of sealer at 4 o’clock and 7 o’clock positions 4.0 mm from apex. E, Fifthpoint joins other; master point does not show. Small amount of sealer at 5 o’clock and 7 o’clock 5.0 mm from apex. F, Sixth point added;master point “reappears” 6.0 mm from apex. G, Seventh point in place, no sealer apparent, canal totally obturated, 7.0 mm from apex.Reproduced with permission from Sakhal S et al.382

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the use of a solvent to soften the primary gutta-perchapoint in an effort to ensure that it will better conformto the aberrations in apical canal anatomy. This is avariation of a very old obturation method, the so-called Callahan-Johnston technique first promulgatedby Callahan in July of 1911.383 The problem with theoriginal technique centered around the use of toomuch of the chloroform solvent. Price, a foe ofCallahan, set out to prove how ineffective the Callahanroot fillings were.384 Although Callahan claimed thatthe mixture of chloroform, rosin, and gutta-percha didnot shrink, Price observed a 24% decrease in volume invitro. The chloroform had evaporated leaving pow-dered gutta-percha.

Today’s use of solvents is quite modest in compari-son with the older methods. Usually only the tip of thepoint is dipped in the solvent and then only for 1 sec-ond (see Figure 11-50, A). Two or three dips will causeserious leakage.385

In this technique the primary point is blunted andfitted 2.0 mm short of the working length. It is thendipped in the solvent for 1 second and set aside whilesealer is placed in the canal. This allows the solvent topartially evaporate. Too much solvent, as with a two- orthree-dip method, will materially increase leakage. Notonly does the gutta-percha volume shrink as the sol-vent evaporates in the canal, the sealer leaks as well,probably because of solvent dissolution.385

614 Endodontics

To begin the obturation by lateral compaction, onemust immediately position the customized masterpoint to its full measured length and then spread itaside to allow the softened gutta-percha to flow. Thespreader is rotated out and is followed by additionalpoints, spreader and points. Because 2.0 mm of themaster tip have been solvent softened, it will flow toplace to produce “smooth, homogeneous, well-con-densed gutta-percha fills closely adapted to the internalcanal configuration in the apical third, including thefilling of lateral canals, fins, and irregularities.”385 AnIsraeli group warns, however, that the point should bepositioned and spread within 15 seconds of being soft-ened; otherwise, it will have lost its plasticity. After 30seconds of air drying, it changes shape.386

The principal solvent used in this technique is chlo-roform. At one time there was concern that it was car-cinogenic, but it has recently been cleared for clinicaluse in dentistry by the FDA, Occupational Safety andHealth Administration, and ADA.387 In any event,other solvents such as eucalyptol, halothane, xylene,and rectified turpentine have been evaluated as substi-tutes for chloroform.388

In addition to the popular dip technique, sealers areprepared by dissolving gutta-percha in these solvents aswell as in rosin and balsam. These mixtures have longbeen popular as sealers and dips for gutta-percha points.Such mixtures are called chloropercha, Kloropercha, or

Figure 11-53 Comparative results of lateral compaction following well-compacted versus poorly compacted root canal fillings. A, Completehealing 1 year after treatment despite overfilling with gutta-percha. (Spaces are artifacts). B, Periradicular granuloma developing 75 days fol-lowing poorly compacted root filling. Bacteria and necrotic debris left in canal. Reproduced with permission from Malooley J et al.345

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eucapercha. Sealers such as CRCS (Calciobiotic RootCanal Sealer) and Wach’s Sealer, respectively, contain thesolvents oil of eucalyptol and Canada balsam.

Efficacy of Solvent-Customized Gutta-perchaMaster Points. As the University of Washingtongroup noted, customizing master points with solventsimproves the seal of gutta-percha.385 At the Universityof Iowa, researchers found essentially the samething.389 Peters found virtually no solubility in distilledwater after 2 years when the chloroform dip methodwas used with lateral compaction.389a

Goldman found Kloropercha as a sealer superior tochloropercha or lateral compaction with ZOE sealer.390

Kloropercha contains balsam, rosin, and zinc oxide inaddition to gutta-percha and chloroform, which makesit more homogeneous. The US Army Research Institutealso tested chloropercha and Kloropercha. Initially, withthe solvent/gutta-percha filling, they achieved dramaticresults (Figure 11-54, A). After 2 weeks, however,chloropercha shrank 12.42% and the Kloropercha4.68%, whereas the simple chloroform dip shrank only1.4%. The comparative results versus lateral and verticalcompaction were dramatic391 (Figure 11-54, B and C).

Morse and Wilcko recommend eucalyptol as a sol-vent to form euchapercha. It shrinks 10% less thanchloropercha.392,393 Others found the quick-dip tech-nique superior to euchapercha as a sealer.394

Halothane and eucalyptol, as alternatives to chloro-form, were found to be no better in dissolving or seal-ing ability.395–397 However, Morse and the TempleUniversity group used eucapercha as a sealer and notedthat it shrinks less than warm gutta-percha or gutta-percha/chloropercha.398

A Tel Aviv group summarized best the value of cus-tomized master points softened by solvents. Theyfound that chloroform-dipped points provided a sig-nificantly better seal than standardized points whenobturating “flat” canals.399 Few canals are perfectlyround in shape.

Vertical Compaction of Warm Gutta-percha*

Over 30 years ago, Schilder introduced a concept ofcleaning and shaping root canals in a conical shape andthen obturating the space “three-dimensionally” withgutta-percha, warmed in the canal and compacted ver-tically with pluggers.400 It was his contention that all the“portals of exit” were clinically significant and would beobturated with a maximum amount of gutta-perchaand a minimum amount of sealer (Figure 11-55).

Obturation of the Radicular Space 615

Figure 11-54 Compaction results from three methods of obturation purposely done without sealer. A, Chloropercha filling presents bestimmediate appearance. Unfortunately, a 12.4% shrinkage follows, leading to massive leakage. B, Lateral compaction—cold gutta-perchashowing coalescence of primary and accessory points at apex but separating midcanal. C, Warm gutta-percha/vertical compaction. Filling ishomogeneous; replication is excellent. Reproduced with permission from Wong M et al.409

*John West gratefully acknowledges the assistance of HerbertSchilder and James Clark in preparing this section.

A B C

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Fitting the Master Gutta-percha Cone. Followingthe preparation of a thoroughly cleansed and continu-ously tapering canal,401 the critical step of fitting themaster cone is the next important feature of this tech-nique. For this, the conventional cone-shapedgutta-percha points are used, not the standardizednumbered points. The cone-shaped gutta-percha moreclosely mirrors the tapered canal shape (Figure 11-56).The primary cone is virtually tailor fit, particularly inthe apical third (Figure 11-57).

The cone is placed to reach the radiographic termi-nus and then cut back slightly short (0.5–1.0 mm) ofthis length (see Figure 11-57). This allows heat moldingof the round cone into the nonround portal of exit andminimizes sealer/tissue contact (Figure 11-58). Undercone-fit guidelines, the shorter, wider, and straighterthe canal, the farther the cone should be cut back fromthe radiographic terminus. Conversely, the longer,

616 Endodontics

more curved, and narrower the canal, the closer thecone should fit to the radiographic terminus. Beginnersoften cut back the cone too much.

Occasionally the cone fit does not reach the apex. Inthis event, one should attempt a smaller cone or, betteryet, improve the shape of the canal. In short, fit thecone 0.5 to 1 mm short of the radiographic terminusand it should possess good tugback.

As stated earlier, fit of the master cone is the key tosuccess in this technique—a successful relationshipbetween the radicular preparation and the master cone.Cleaning and shaping and obturation are clinicallyinseparable. When the gutta-percha is subsequentlywarmed and compacted, it fills not only the critical partsof the canal but the cleaned portals of exit as well (seeFigure 11-57, C). When compacted, the primary coneprovides the body of the warm “wave of compaction”moving apically and then a warm wave of compactionmoving coronally. The cone must fit tightly in the apicalthird, that is, have “tugback,” and have diminished tapertoward the middle and coronal thirds as well.

It is typical of vertical compaction that more than oneportal of exit per canal will be filled—two portals of exitper canal in one sampling.402 In the graduate endodon-tic clinic at Boston University, more than one foramen isfilled over 40% of the time.381 Similar results are report-ed at the University of Washington (Figure 11-59).403

There is virtually no risk of compacting too short or toolong if the first cone fits properly.404

Prefitting the Vertical Pluggers. Practitioners ofwarm gutta-percha vertical compaction prefer using aset of pluggers designed by Schilder (Dentsply/Maillefer; Tulsa, Okla.), a wider plugger for the coronalthird of the canal, a narrower plugger for the middlethird, and the narrowest plugger for the apical third ofthe canal. The objective is for the widest appropriate

Figure 11-55 Warm gutta-percha/vertical compaction. Root canalsystem anatomy is “discovered” during compaction; see multipleportals of exit. (Courtesy of Dr. John D. West.)

Figure 11-56 Comparison in shape and size between pulp and traditional gutta-percha cones. A, Conical pulp extirpated from 10-year-oldboy. Note enormous lateral canal. B, Traditional (nonstandardized) gutta-percha cone similar in taper and bulk to pulp anatomy. (Courtesyof Dr. John D. West.)

A B

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plugger to capture the maximum cushion of warmgutta-percha as the heat wave is carried apically.405

Only one or two pluggers may be needed for shorterteeth, whereas three or four are used in longer canals.Most cases require three graduated sizes.

Schilder pluggers are marked with serrations every 5mm, so that the depth that each instrument penetrates

should be recorded by plugger number and depth ofpenetration. The pluggers are then set aside for imme-diate use.

Heat Transfer Instrument. Initially, an instrumentdesigned much like a spreader was used to transfer heatfrom a Bunsen burner to the gutta-percha. It was heated“cherry-red,” immediately carried into the canal, sub-

Obturation of the Radicular Space 617

Figure 11-57 Fitting the master gutta-percha cone. A, Cone fit to radiographic terminus. B, Cone is cut back 0.5 mm. When placed to depth,the incisal reference remains the same. C, Compaction film reveals two apical foramina as well as large lateral canal opposite lateral lesion.(Courtesy of Dr. John D. West.)

Figure 11-58 Warm gutta-percha conforming to “egg-shaped” canal. A, Primary gutta-percha cone fits 0.5 to 1.0 mm short of radiograph-ic apex. B, Cold plugger advances the thermoplasticized gutta-percha into apical constricture. C, Vertical pressure compacts warmedgutta-percha into nonround foramen. (Courtesy of Dr. John D. West.)

A B C

A B C

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merged into the mass of gutta-percha, and drawnthrough the gutta-percha for 2 or 3 seconds to allow theheat to transfer from the heat carrier. It was then with-drawn in a slightly circular wiping motion, “freezing”some of the gutta-percha onto the heat carrier. Successivewaves of vertical compaction immediately followed.

The Schilder heat carrier has been essentially super-seded by the Touch ’n Heat 5004 (SybronEndo/Analytic;Irvine, Calif.), an electronic device specially developedfor the warm gutta-percha technique (Figure 11-60). Itexhibits the same thermal profile as the original heat car-rier but has the advantage of generating heat automati-cally at the tip of the instrument. Battery or AC modelsare available.

Root Canal Sealer. Practitioners of this techniquegenerally prefer using Kerr Pulp Canal Sealer, Richert’s

618 Endodontics

original ZOE cement that contains rosin as well as pre-cipitated silver used as a radiopaquing medium. Theadvantages, they feel, are the short setting time and lowresorbability.406 Recently, Kerr introduced Pulp CanalSealer EWT, which allows for Extended Working Time.

Step-by-Step Procedure of Vertical Compaction ofWarm Gutta-percha

1. Dry the canal! This is best achieved by using 100%alcohol irrigated deep within the root canal systemusing thin, safe-tipped irrigating “needles.” The canalis then dried with paper points and air dried with theStropko irrigator (SybronEndo/Analytic Tech; Irvine,Calif.). Confirm the patency of the foramen with aninstrument smaller than the last size instrument usedto develop the apical preparation.

2. Fit the appropriate gutta-percha cone to the patentradiographic terminus. It should visually go to fullworking length and exhibit tug-back. Confirm theposition radiographically. Cut off the butt end ofthe cone at the incisal or occlusal reference point(Figure 11-61, A).

3. Remove the cone and cut back 0.5 to 1.0 mm of thetip, reinsert, and check the length and tug-back. Thecone’s apical diameter should be the same diameteras the last apical instrument to reach the radi-ographic terminus of the preparation (Figure 11-61,B). Remove the cone, dip it in alcohol, and curve itslightly by drawing it through a folded 2 × 2 gauze sothat it will more easily follow the probable curvedshape of the canal. Set the cone aside.

4. Prefit the three pluggers to the canal preparation: firstthe widest plugger to a 10 mm depth (Figure 11-61,C); next, the middle plugger to a 15 mm depth(Figure 11-61, D); finally, the narrowest plugger towithin 3 to 4 mm of the terminus (Figure 11-61, E).Record the lengths of the desired plugger depth.

5. Deposit a small amount of root canal sealer in thecanal with a Handy Lentulo spiral. (Dentsply/Maillefer; Tulsa, Okla.). Lightly coat all of the walls.

6. Coat the apical third of the gutta-percha cone with athin film of sealer.

7. Grasp the butt-end of the cone with cotton pliersand slide the cone approximately halfway down thecanal. Then gently follow it fully into place with theclosed tip of the cotton pliers (Figure 11-61, F). In acurved canal, the cone will rotate as it responds tothe curvature.

8. Using the Touch ’n Heat 5004 heat carrier, sear offthe cone surplus in the pulp chamber down to thecervical level (Figure 11-61, G). This transfersheat to the coronal third of the gutta-percha cone

Figure 11-59 Four-canal maxillary second molar. Secondmesiobuccal canal in mesiobuccal root has separate portal of exit.(Courtesy of Dr. John D. West.)

Figure 11-60 “Touch ’n Heat” 5004, battery-powered (recharge-able) heat source. Heat carrier heats to glowing within seconds toplasticize gutta-percha in canal. Also used in removal of gutta-per-cha for postpreparation or re-treatment. (Courtesy of SybronEndo/Analytic Tech., Irvine, Calif.)

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and creates a platform to begin the first wave ofcompaction.

9. Using the widest vertical plugger that has previous-ly been coated with cement powder as a separatingmedium, the gutta-percha is folded into a mass andcompacted in an apical direction with sustained 5-to 10-second pressure (Figure 11-61, H). This is thefirst heat wave. The temperature of the gutta-perchahas been raised 5 to 8˚C above body temperature,which allows deformation from compaction. At thistemperature (42 to 45˚C), the gutta-percha retainsits same crystalline beta form with minimal shrink-age as it cools back to body temperature.

10. The second heat wave begins by introducing theheat carrier back into the gutta-percha, where itremains for 2 to 3 seconds (Figure 11-61, I) and,when retrieved, carries with it the first selectivegutta-percha removal (Figure 11-61, J).

11. Immediately, the midsized coated plugger is sub-merged into the warm gutta-percha. The verticalpressure also exerts lateral pressure. This fillingmass is shepherded apically in 3 to 4 mm waves cre-ated by repeated heat and compaction cycles(Figure 11-61, K).

12. The second heating of the heat carrier warms thenext 3 to 4 mm of gutta-percha and again anamount is removed on the end of the heat carrier(Figure 11-61, L).

13. The narrowest plugger is immediately inserted inthe canal and the surplus material along the walls isfolded centrally into the apical mass so that the heatwave begins from a flat plateau. The warmedgutta-percha is then compacted vertically, and thematerial flows into and seals the apical portals ofexit (Figure 11-61, M).

14. The apical “down-pack” is now completed, and if apost is to be placed at this depth, no moregutta-percha need be used (Figure 11-61, N).

15. “Backpacking” the remainder of the canal completesthe obturation. The classic method of backpackingconsists of placing 5 mm precut segments ofgutta-percha in the canal, cold welding them withthe appropriate plugger to the apical material(Figure 11-61, O), warming them with the heat-car-rier (Figure 11-61, P), and then compacting. Itshould be noted that no selective removal ofgutta-percha is attempted in the backpacking(Figure 11-61, Q). This sectional procedure is con-tinued with heat and the next wider plugger untilthe entire canal is obturated (Figure 11-61, R).

16. An alternative method of backpacking may be doneby injecting plasticized gutta-percha from one of the

syringes, such as Obtura II (Obtura/Spartan, USA).In any event, the plasticized gutta-percha must becompacted with vertical pluggers to ensure its flowagainst canal walls, to weld it to the apical materials,and to minimize shrinkage (Figure 11-61, S).

17. The final act involves the thorough cleansing of thepulp chamber below the CE junction, the additionof an appropriate barrier, and the placement of apermanent restoration (Figure 11-61, T). In molarteeth, extra sealer should be placed in the chamberarea, warm gutta-percha is syringed into the cham-ber flow, and the gutta-percha is compacted withlarge amalgam pluggers to ensure that any furcalportals of exit will be filled prior to final restoration(Figure 11-62).

Like all dental techniques, vertical compaction ofwarm gutta-percha is technique sensitive. It is impera-tive, therefore, to seek professional training in this spe-cial obturation method.407

Efficacy of Vertical Compaction of Warm Gutta-percha. Warm gutta-percha, vertically compacted,has proved most effective in filling the canals of severe-ly curved roots and roots with accessory, auxiliary, orlateral canals, or with multiple foramina. Since the firstindication of such anatomic variations may beobserved during the filling procedure, it behooves thedentist to use a filling technique that ensures obtura-tion in case such unusual canals are open and patent.

The chief proponents of the warm gutta-perchatechnique at Boston University point out that consis-tent success in obturation will be achieved only whenthe canal is properly cleaned and shaped, and whencopious amounts of sodium hypochlorite are used toflush away the debris, bacteria, and dentinal filings.408

After this proper preparation, predictable three-dimen-sional obturation with vertical compaction is easilyaccomplished. In this technique, the two concepts,cleaning and shaping and three-dimensional obtura-tion, are inseparable.

As previously stated, very few microleakage studieshave been done comparing warm gutta-percha/verticalcompaction with other techniques. Lateral compactionis usually used as a control in these studies. The fewthat do exist, however, speak favorably for warm/verti-cal compaction.

Brothman compared lateral and vertical techniquesand found “no statistically significant difference in fillingefficiency.”356 He reported, however, a significantly greaterincidence of accessory canal filling with sealer by verticalcompaction. He concluded that ribbon-shaped canalswere better filled by lateral compaction, whereas “for cen-

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tric canals, vertical condensation appears better.”356

Reader and Himel reported “significantly more gutta-per-cha in the lateral canals” when compared with cold lateralor warm lateral/vertical compaction.357 Torabinejad et al.compared a number of obturation techniques and con-cluded that comparable results were achieved with all fourmethods, but reported close adaptation in the middle andapical thirds by the vertical method.358 Wong et al. report-ed a homogeneous filling with excellent replication.409 AtDalhousie University, three obturation methods werecompared and all three “techniques proved equally satis-factory,” although the researchers did note “cold-welds”with vertical compaction.352 Lugassey and Yee also notedthe cold welds as well as “microscopic voids, folds and

620 Endodontics

inclusions scattered randomly throughout the rootcanal.”410 A US Army group tested three different meth-ods and found the differences in radioactive microleakageto 45Ca were not significant.353

A tendency to overfill the canal while using thewarm gutta-percha/vertical compaction technique wasnoted by a Lebanese group who reported that “apicalcone displacement was greater with vertical com-paction.” Clinically, they observed that “overextensionis more likely to occur…when the master cone isadapted only 0.5 mm short.” There were no overexten-sions with lateral compaction.411

Schilder has twice reported to meetings of theAmerican Association of Endodontists his evaluations

Figure 11-61 Technique of warm gutta-percha/vertical compaction. A, Master gutta-percha cone fits tightly to radiographic apex. Markedat incisal edge to establish length reference. B, Master cone cut back 0.5 to 1.0 mm at tip and retried in canal. Trimmed incisal referenceremains same. C, Largest plugger prefit to coronal third of canal. D, Midsize plugger prefit to midcanal without touching walls. E, Smallestplugger prefit to within 3 to 4 mm of radiographic apex. Remains free in canal. F, Kerr Sealer deposited in midcanal with Handy Lentulo spi-ral. Apical third of master cone is lightly coated with sealer and gently teased to place. Incisal reference checked. G, Surplus gutta-percharemoved with heat carrier down to canal orifice. H, Largest plugger compacts warmed gutta-percha into bolus. Midroot lateral canal beingobturated. I, Heat carrier transfers heat 3 to 4 mm into middle third of mass. Wiping carrier against walls softens excess gutta-percha. J, Firstselective gutta-percha removal.

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of success and failure when his recommendations ofcleaning and shaping and obturation with warmgutta-percha and vertical compaction were followed.The cases were done by endodontic graduate studentsat Boston University.

The first was a radiographic study, treatment of 100maxillary anterior teeth with periradicular lesions.412

The lesions ranged in size from 8 to 35 mm. The agerange was 14 to 84 years and involved both sexes.Radiographic observations were made at 6, 12, 18, and24 months. Healing was judged as totally healed (90%),

partially healed (75%), no healing (50%), or worse. Totalhealing or 90% healing was noted in 56% of the caseswithin the first 6 months. At 24 months, 99% of the 100cases “were fully healed.”412 The one failed case (an84-year-old woman) was subsequently revealed by sur-gery to have an apical bifurcation. Apicoectomy belowthe bifurcation allowed normal healing within 1 year.

On the basis of this radiographic study of maxillaryanterior teeth, Schilder reported 100% success after 2years for cleaning and shaping and three-dimensionalobturation by warm gutta-percha/vertical compaction.412

Obturation of the Radicular Space 621

Figure 11-61 (Continued) K, Midsize plugger compacts heat-softened gutta-percha apically. Second lateral canal appears as obturated. L,Heat transfer instrument warms apical gutta-percha. Second selective removal of material. M, Smallest plugger compacts apical mass intoapical preparation and accessory canals now appear obturated as well. N, Plugger folds surplus gutta-percha around walls into flattened cen-tral mass. Radiograph confirms total obturation of apical third of canal. If a post is to be placed, obturation is complete. O, To complete obtu-ration by segmented gutta-percha, a 3 mm blunted section is placed and “cold-welded” with the medium plugger to the apical mass. P, Heatcarrier warms first backpack piece. Q, Warmed backpack piece married by compaction to apical filling. Process is continued to fill entirecanal. R, If gutta-percha gun (Obtura II) is used for backfill, the needle is inserted to the apical segment and then backed out, leaving deposit.Plasticized gutta-percha is compacted to complete obturation to canal orifice. S, Final compaction of backpack done with largest plugger. T,Gutta-percha and sealer are removed to below free gingival level, crown is thoroughly cleansed, and final restoration is placed in the coronalcavity. (Courtesy of Dr. John D. West.)

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As a follow-up to the preceding report, Schilder pre-sented in 1977 a histologic study of 25 lesions ofendodontic origin.413 Intentional surgical biopsy wasscheduled from 1 to 25 months following obturation.The study, however, was terminated at 15 months whenall of the remaining cases appeared healed.

Some interesting histologic observations were madeby Schilder. Within 1 week of canal débridement andeven before obturation, new bone formation was notedat the periphery of a large lesion. Healing alwaysoccurred from the periphery toward the apex. Thepresence or absence of excess sealer, or occasionallygutta-percha, had no observable influence on the inex-orable resolution of the lesions and their replacementwith normal bone. By 12 months, all of the lesions inthe study were fully healed.413

Schilder concluded these two reports with the obser-vation that “failure is the result of inadequate cleaningand shaping of the root canal system and/or inadequateobturation.”413

Quite possibly, the success to be achieved with thistechnique, as with any technique, is highly operatorsensitive. As Kerekes and Rowe so aptly stated, “successof treatment [will] be influenced to a high degree bythe technical skill of the practitioners: practitioners lessexperienced in endodontic treatment have problemscarrying out root fillings to a satisfactory technicalstandard.”354

Finally, something should be said about some of theconcerns voiced about this technique. One is that toomuch stress is introduced into the tooth through verticalcompaction. Early on, researchers at Temple Universityobserved that “when canals were filled by the verticalcondensation method, more cracks in the dentin werediscernible than were seen in the teeth filled by lateral

622 Endodontics

condensation.”414 Schilder replied that the cracks seen inthe Temple University microphotographs were laborato-ry artifacts (H. Schilder, personal communication,August 1977). More recently, a US Army study done withmathematical models and “finite element analysis” sug-gested “that lateral condensation may be more likely toproduce undesirable stress concentrations than is verti-cal condensation.” These researchers also said that theterm “lateral condensation may be somewhat of a mis-nomer,” that it produced more stress with less force nearthe apex (where a root is finer and more likely to frac-ture) than did vertical compaction. However, “the aver-age stress throughout the entire canal was higher for ver-tical condensation…”324 A group at the University ofIowa tested both lateral and vertical compaction tech-niques for stresses induced and concluded that “thehighest stress concentrations occurred in the apical thirdof the root…and progressed incisally.” Both lateral andvertical stresses were culpable.340

Another concern relates to the temperatures gener-ated within the canal from the warming process. TheBoston University group found the maximum tem-perature in the body of the canal to be 80˚C (176˚F),whereas in the apical region the temperature peakedat 45˚C (113˚F).415 A US army group reported that“the use of hot instruments for the condensation offilling material did not appear to endanger theintegrity of the lateral periodontium.”416 In laterresearch, an Army group again studied intracanaltemperatures, produced this time with the Touch ’nHeat unit. They felt the operator should restrict theuse of the unit to lower power settings of #2 or #3 andincrease the length of time the heated tip is activated.They warned that at the top setting of #6 the unitcould increase the intracanal temperature to as highas 114.51˚C, a potentially damaging temperature.417

Lee et al., at the University of Illinois, remarked that“the critical level of root surface heat required to pro-duce irreversible bone damage is believed to be >10˚ C.” In this context, they noted that “cautionshould be used with the Touch ’n Heat and flameheated carriers on mandibular incisors.”418

System B: Continuous Wave of Obturation

Buchanan, long an impressive advocate of the warmgutta-percha vertical compaction technique, has devel-oped a variation of the method that he perceives asfaster and more accurate. Concerned with the com-plexity and time consumed in completing an obtura-tion, he retained the principles of vertical compactionbut improved the methodology. Working with AnalyticTechnology, which had developed the Touch ’n Heat

Figure 11-62 Furcal accessory canal and lateral canal, mesial rootfilled by vertical compaction of warm gutta-percha. (Courtesy ofDr. John D. West.)

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device for warming gutta-percha in the canal,Buchanan and Analytic perfected the System-B HeatSource and associated pluggers (SybronEndo/Analytic;Irvine, Calif.). This new heat source monitors the tem-perature at the tip of the heat-carrier pluggers, thus“delivering a precise amount of heat for an indefinitetime.”419

System B obturation is predicated on a precisepreparation, perfectly tapered to match as closely aspossible the shape of the nonstandardized gutta-perchacones-fine, fine-medium, medium, and medium-large(F, FM, M, and ML). Another Buchanan/Analyticdevelopment is gutta-percha cones that match theshape produced during canal preparation usingGreater Taper instruments.

Downpack Technique. An appropriate size gutta-percha cone, matching the completed preparationshape, is tested in the canal to be sure it goes fully toplace. This is confirmed radiographically. “ContinuousWave Technique requires good canal shape and metic-ulous gutta-percha cone fitting. The cone must fit in itslast 1 mm, and fit to full length before minimal cutback(less than 0.5 mm).”419 The cone is then removed andthe corresponding plugger is tried for size in the canal.It should stop at its “binding-point,” about 5 to 7 mmshort of the working length. The stop attachment isthen adjusted at the coronal reference point and theplugger is removed and attached to the Heat Source.The canal is dried.

The primary point is coated with sealer and pushedinto place, all the way to the apical stop. The HeatSource is activated, set for “use” and “touch,” and thetemperature is set for 200˚C and the power dial at 10.The cone is then seared at the orifice with the preheat-ed plugger tip, and the preheated plugger is then “driv-en” smoothly through the gutta-percha to within 3 to 4mm of its binding point in the canal. This will takeabout 2 seconds. Maintaining apical pressure, the plug-ger will continue to move apically, and at this time theheat switch is released. The plugger is held there, cold,under sustained pressure, for an additional 10 seconds.It is during this period the gutta-percha flows to theapical matrix and into accessory canals. The pressurealso compensates for the shrinkage that might occur asthe mass cools.

To remove the plugger: while still maintaining apicalpressure, the heat switch is activated for only 1 secondfollowed by a 1-second pause. The “cold” plugger is thenquickly withdrawn. Following radiographic confirma-tion, the remainder of the canal is now ready for backfill.

Backfill Technique. Using the same size gutta-per-cha cone and plugger, the cone is coated with sealer and

positioned in the backfill space in the canal. The SystemB temperature is now set at 100˚C. Preheat the pluggerout of the canal for only 1⁄4 second, cut the heat, butimmediately plunge the plugger into the backfill coneand hold it in place for 3 to 5 seconds as the gutta-per-cha cools. Another cone is added in the backfill spaceand heat is again applied. The final plugging is donewith a large cold regular plugger. Another method ofbackfilling is to use the Obtura II gutta-percha gun.

To date there have been few reports on the success ofthe System B Technique. On the other hand, concernhas been expressed about the 200˚C heated plugger sonear the thin root at the apex. The short period of timethis high heat is delivered, however, seems to precludeany periodontal damage.

Warm/Sectional Gutta-percha Obturation. Theuse of small warmed pieces of gutta-percha, theso-called sectional obturation technique, is one of theearliest modifications of the vertical compactionmethod described earlier. Webster might well havebeen describing this procedure in 1911 when he spokeabout filling “with gutta-percha, using points heatedand well packed in with hot instruments.”228

Eventually this became known as the “Chicago” tech-nique since it was widely promoted by Coolidge,Blayney, and Lundquist, all of Chicago. It was also thefavorite technique of Berg of Boston.420

The method begins like other methods: fitting theplugger to the prepared tapered canal (Figure 11-63,A). It should fit loosely and extend to within 3 mm ofthe working length. A silicone stop is then set on theshaft marking this length (Figure 11-63, B). Next, theprimary gutta-percha point is blunted and carried toplace. It should be fitted 1 mm short of the workinglength and confirmed radiographically (Figure 11-63,C). Upon removal, 3 mm of the tip of the point arecleanly excised with a scalpel (Figure 11-63, D) and thissmall piece is then luted to the end of the warmed plug-ger (Figure 11-63, E). Sealer is placed, lining the canal,the gutta-percha tip is warmed by passing it through analcohol flame, and it is then carried to place. Under api-cal pressure, the plugger is rotated to separate thegutta-percha (Figure 11-63, F) and it is thoroughlypacked in place. At this point, it is best to expose a radi-ograph to be sure the initial piece is in position (Figure11-63, G). If so, the remainder of the canal is filled in alike manner, compacting additional pieces of warmedgutta-percha until the canal is filled to the coronal ori-fice421 (Figure 11-63, H).

If a post is planned, the compaction can stop after thesecond piece, leaving 5 to 6 mm of apical canal filled.Another variation of heat-softening the gutta-percha is

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to soften each piece in chloroform or halothane in aquick “dip.”

Rather than laboriously adding sections ofgutta-percha, backfilling may be done with thermo-plasticized gutta-percha from one of the gutta-percha“guns.” In evaluating such backfill, Johnson and Bondnoted that “it may be clinically acceptable to backfillcanals up to 10 mm in a single increment using sealerand the Obtura II gutta-percha system.”422

Lateral/Vertical Compaction of Warm Gutta-percha.Considering the ease and speed of lateral compaction aswell as the superior density gained by vertical com-paction of warm gutta-percha, Martin developed adevice that appears to achieve the best qualities of bothtechniques. Called Endotec II (Medidenta Inc;Woodside, N.Y.), the newly designed device is a battery-powered, heat-controlled spreader/plugger that ensurescomplete thermo-softening of any type of gutta-percha.It is supplied with two AA batteries that provide theenergy to heat the attached plugger/spreader tips(Figure 11-64). The quick-change, heated tips are sizedequivalent to a No. 30 instrument, are autoclavable, andmay be adjusted to any access angulation. Martin claimsthat the “Endotec combines the best of the two mostpopular obturation techniques: warm/vertical and therelative simplicity of lateral compaction” (H. Martin,personal communication, December 1999).

Canal cleaning and shaping for this technique is acontinuous taper design with a definite apical stop.

624 Endodontics

After the primary point is fitted to full working length,the hand spreader and the Endotec plugger/spreaderare fitted as well. At this point, silicone stops are placedto mark the length of canal.

After drying of the canal, a limited amount of sealeris applied. The primary point is then firmly positionedand gently adapted with a hand or finger spreader. Ithas also been recommended that one or two addition-al gutta-percha points be placed to reduce the possibil-ity that the warm plugger will loosen the point whenthe tip is retracted.

Figure 11-63 Sectional gutta-percha obturation. A, Canal prepared with flare. B, Plugger preselected to fit loosely in canal and extend towithin 3 mm of working length. C, Master gutta-percha point fitted to within 1.0 mm of working length. Confirm by radiograph. D,Gutta-percha is removed and 3 mm of apical point are excised (arrow). E, Plugger is warmed in alcohol flame and point is luted to plugger.Gutta-percha is warmed by passing through alcohol flame and quickly coated with cement. F, Warm gutta-percha is carried to place; plug-ger is rotated to loosen and then used for compaction. G, Radiograph should confirm well-condensed apical filling. H, Remainder of canalis filled by lateral or vertical condensation, by Compactor or Obtura. (Courtesy of Dr. Ahmad Fahid.)

Figure 11-64 Endotec II handpiece contains battery power pack.Button initiates heat in attached plugger. (Courtesy of Medidenta,Inc.)

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At this juncture the Endotec plugger is placed in thecanal to full depth. The activator button is pressed andthe heating plugger is moved in a clockwise motion.The heat button is then released and the plugger coolsimmediately. It is now removed from the gutta-perchawith a counterclockwise motion. This lateral com-paction has formed a space for an additional point tobe added, after which the plugger is again placed, heat-ed, moved clockwise for 10 to 15 seconds, cooled, andretracted counterclockwise (Figure 11-65). Now theplugger can be used cold to compact the softenedgutta-percha, followed again by warming and lateralspace preparation for additional points.

In this manner (lateral compaction with the heatedplugger to provide space for additional gutta-percha,and the vertical compaction with the cooled plugger tocondense the heat-softened gutta-percha) the canal isentirely obturated. Finally, a cold hand plugger can beused to firmly condense the fused gutta-percha bolus.

The Endotec can also be used to soften and removegutta-percha for post preparation or in the event of re-treatment. An Air Force group also found they could

measurably improve compaction while obturating amandibular molar with a C-shaped canal by using theEndoTec in what they termed a “zap and tap” maneu-ver: preheating the Endotec plugger for 4 to 5 secondsbefore insertion (zap) and then moving the hot instru-ment in and out in short continuous strokes (taps) 10to 15 times. The plugger was removed while still hot,followed by a “cold spreader with insertion of addi-tional accessory points.”423

Concern has been voiced that heat from the tip willdamage the periodontium, and that the lateral/verticalpressure exerted will be too stressful. In the first instance,it was found there was “no heat related damage to peri-odontal tissues from either of the two methodsemployed”: Endotec and warm/vertical compaction.424

A US Army group also tested for heat damage from theTouch ’n Heat unit, which produces more heat (816˚C)than the Endotec. They pointed out that even though theinternal gutta-percha mass reached 102˚C, gutta-perchaand dentin are poor heat conductors, and this tempera-ture “would not be of sufficient magnitude to causedamage in the periodontal tissues.”425

In the second instance, that of stress development,Martin and Fischer have shown, in a photoelastic stresstest, that “warm lateral condensation (Endotec) createdless stress during obturation than did cold lateral con-densation.”373

Efficacy of the Warm/Lateral Technique. Becausegutta-percha is heated with this technique, there mustbe a commensurate shrinkage when it cools. This factalone would bring into question the density of the finalfilling. However, Martin point out that the Schildercompaction method leads to 0.45% shrinkage, andsince Endotec temperatures are lower than with theother technique, shrinkage following Endotec usageshould be lower as well.426

A US Army group evaluated the quality of the apicalseal produced by lateral versus warm lateral com-paction and found no significant difference in leak-age.359 In contrast, Kersten, in Amsterdam, reportedthat “Endotec had significantly less leakage than any offour other methods.”372 Ewart and Saunders, inGlasgow, found much the same.427

Himel and Cain, at Tennessee, achieved the bestresult with the Endotec if they condensed thegutta-percha bolus five times with the cold pluggerafter each warming with the plugger heated. This prac-tice filled lateral and accessory canals as well: “thegutta-percha was not melted but soft enough it wouldflow into fins and ramifications.”428 A US Army groupreported they could improve the density (by weight) oflaterally compacted canals by 14.63% by a follow-up

Obturation of the Radicular Space 625

Figure 11-65 Motion for using Endotec II- plugger/spreader—vertical pressure with sweeping lateral pressure. Additionalgutta-percha points will be added. (Courtesy of Dr. HowardMartin.)

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use of the Endotec. A second use added another 2.43%of gutta-percha.429

As far as tissue reactions to the technique are con-cerned, Castelli et al. found that “some Endotec speci-mens generated small restrictive inflammatory infil-trates restricted to the root canal opening,” whereas thewarm gutta-percha “vertical condensation inflamma-tory reactions, because of their extensive nature, wereprobably the source of maintaining discomfort andpain.”424

Thermomechanical Compaction of Gutta-percha.A totally new concept of heat softening and compact-ing gutta-percha was introduced by McSpadden in1979. Initially called the McSpadden Compactor, thedevice resembled a reverse Hedstroem file, or a reversescrew design. It fit into a latch-type handpiece and wasspun in the canal at speeds between 8,000 and 20,000rpm. At these speeds, the heat generated by frictionsoftened the gutta-percha and the design of the bladesforced the material apically. In experienced hands,canals could be filled in seconds.

626 Endodontics

However, problems developed and the Compactor fellinto disfavor. Fragility and fracture of the instruments,along with overfilling because of the difficulty in master-ing the technique, led to its demise. However, phoenix-like, it rose again in different shapes and forms. InEurope, Maillefer modified the Hedstroem-type instru-ment as the Gutta-Condenser, and Zipperer (Germany)called its modification the Engine Plugger. The lattermore closely resembles an inverted K-file.

McSpadden, in the meantime, modified his originalpatent and brought out a newer, gentler, slower-speedmodel. It is now supplied as an engine-driven instru-ment made of nickel titanium (see Figure 11-66) andpresented as part of the Microseal System (Analytic/Quantec, USA). Because of their flexibility, the NiTi con-densers may be used in curved canals.

The Microseal Condenser is used in conjunctionwith heat-softened, alpha phase-like gutta-percha aswell as regular gutta-percha points. Of course, sealer isalways used. To obturate a canal, the clinician is advisedto place the primary gutta-percha point, followed bythe appropriate size Condenser (one that will reachnear the working length), which has been coated withthe heat-softened gutta-percha (Figure 11-67). TheCondenser is spun in the canal with a controlled speedhandpiece at 1,000 to 4,000 rpm to form a firmer core.This “flings” the gutta-percha laterally and vertically(Figure 11-68).

McSpadden has developed a technique to fillopen-apex cases as well by initially depositing a bolusof low-heat gutta-percha at the apex with a large con-denser. This is allowed to cool and harden to form anapical plug against which the remaining canal is obtu-rated with gutta-percha points and additionalheat-softened gutta-percha.430

To date, this particular technique—combining thereverse screw-type condenser with warmed alphagutta-percha—has not been widely reported in US lit-erature; however, the technique is popular in Europe,with some reporting from there.

Efficacy of the Thermomechanical CompactionMethod. The original McSpadden compactor waswell studied in the 1990s, and these findings are nottotally moot because a modification is being distributedas the Brasseler TLC (Thermal Lateral Condensation) aswell as the aforementioned European models, theMaillefer Gutta-Condensor and the Zipperer EnginePlugger. These instruments have enjoyed a good deal ofuse, particularly for “backfilling” after the initial verticalor lateral compaction is complete.

This latter method has been termed the hybrid tech-nique by Tagger et al. of Tel Aviv.375 They first coat their

Figure 11-66 Micro-Seal Gutta-percha Condenser is operated atslow speed. The reverse-screw action compacts plasticizedgutta-percha apically and laterally. (Courtesy of SybronEndo/Analytic-Quantec.)

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regular primary point with sealer, move it to place, andspread it aside with a finger spreader followed by anaccessory point. They then place an Engine Plugger,size 45 or 50, 4 or 5 mm into the canal and rotate it at15,000 rpm. After 1 second, it is advanced into thecanal until resistance is met and then slowly backed outwhile still rotating. Only 2 or 3 seconds are involved tocompletely fill the canal.

Comparing the hybrid technique with lateral con-densation, Tagger et al. reported significantly less api-cal leakage with the hybrid technique.375 They previ-ously had reported no significant difference in leakagewhen they used thermomechanical compaction alone(not the hybrid technique) versus lateral com-paction.361 Some agreed,360,374,431 whereas othersfound thermomechanical compaction improved theapical seal.371,376

Saunders at the University of Dundee found that“the Hybrid method would be the technique of choice.”He found that it was “quicker to complete than con-ventional lateral condensation, should carry a reducedrisk of fracture to slender roots and is relatively easy tomaster.” Overfilling is also less likely.432

Concern has been expressed about the intracanalheat generated during thermomechanical compaction.Could it be damaging to the periodontium? Hardie atthe University of Dundee recorded in vitro “rises intemperature up to 27˚C” on the external midsection ofroots. She voiced a need for caution if a 4-second appli-

Obturation of the Radicular Space 627

Figure 11-67 A, Loading plasticized Phase II gutta-percha ontoMicro-Seal Condenser already coated with Phase I gutta-percha. B,Obturation of curved and accessory canals using Condenser and PhaseI and II gutta-percha. (Courtesy of Analytic/Quantec Endodontics.)

A

B

Figure 11-68 A, Remarkable flexibility of nickel-titanium condenser allows careful rotation in curved canals at very slow speed. B, Final fill-ing by Condenser. (Courtesy of Dr. John McSpadden.)

A B

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cation of a spinning compactor could produce thismuch rise in temperature.433 Saunders, also at Dundee,performed in vivo hyperthermia studies on ferretsusing an Engine Plugger at 10,000 rpm. He found amedian 18.31˚C temperature rise during use, whichthen dropped to a 1.25˚C rise in 1 minute.434 He alsoexamined these specimens histologically 20 days aftertesting and found resorption of cementum in 20% ofthe specimens. At 40 days he found about 25% exhibit-ed resorption as well as ankylosis of bone to cementumand sounded a note of caution.435

In Sweden, with workers using the compactor for 8seconds, temperature increases as much as 50˚C (35˚Cmean) were recorded. They, too, felt that “periodontalcomplications from thermomechanical condensation arepossible.”436 At the University of Florida, a group statedthat higher speeds or longer duration than recommend-ed could “cause an adverse temperature rise…and adetrimental effect upon the quality of the seal.”437

These “outer-limit” studies lead one to conclude thatcare must be used, “kinder and gentler,” in any of thesemechanical, heat-generating methods. On the other

628 Endodontics

hand, they make a case for the less aggressive method:slower-speed, lower-temperature plasticized gutta-per-cha that can be placed with less stress to the tooth, yetprovide optimal obturation.

Thermomechanical Solid-Core Gutta-perchaObturation. One other innovation using the thermo-mechanical principle to compact gutta-percha in theroot canal has been introduced as the J.S. Quick-Fill(J.S. Dental Co., Sweden/USA). This system consists oftitanium core devices that come in ISO sizes 15 to 60,resemble latch-type endodontic drills, coated withalpha-phase gutta-percha (Figure 11-69). These devicesare fitted to the prepared root canal and then, followingthe sealer, are spun in the canal with a regularlow-speed, latch-type handpiece. Friction heat plasti-cizes the gutta-percha and it is compacted to place bythe design of the Quick-Fill core. After compaction,there are two choices: either the compactor may beremoved while it is spinning and final compactioncompleted with a hand plugger or the titanium solidcore may be left in place and separated in the coronalcavity with an inverted cone bur.

Pallares and Faus, from Valencia, Spain, conductedan apical leakage dye study comparing J.S. Quick-Fillagainst lateral condensation. They found no significantdifference in efficacy; however, they did find with theJ.S. Quick-Fill that the sealer (AH26) adapted moreperipherally against the dentin walls and the gutta-per-cha was more centrally located. The cement had alsopenetrated the dentinal tubules and the lateral andaccessory canals.438 Canalda-Sahli and his coworkers,also from Spain, found that J.S. Quick-Fill could beused successfully to seal root canals in teeth with largestraight canals.439

Ultrasonic Plasticizing. The technique of plasticiz-ing gutta-percha in the canal with an ultrasonic instru-ment was first suggested by Moreno from Mexico.440

He used a Cavitron ultrasonic scaler (Dentsply/Caulk;Milford, Dela.) with a PR30 insert, but because of itsdesign it could be used only in the anterior mouth.Moreno placed gutta-percha points to virtually fill thecanal. He then inserted the attached endodontic instru-ment into the mass, activated the ultrasonic instrument(without the liquid coolant), and as it plasticized thegutta-percha by friction, advanced it to the measuredroot length. Final vertical compaction could be donewith hand or finger pluggers.440

At San Antonio, workers questioned the heat gener-ated by this technique. Would it be damaging? Using theCavitron PR30, they found very little heat rise: 6.35˚C in6.3 seconds. Using an Enac ultrasonic unit (Osada Co.;Los Angeles, Calif. and Japan), however, they recorded a

Figure 11-69 J.S. Quick-Fill titanium carriers coated withalpha-phase gutta-percha comes in four sizes and operates in regu-lar slow-speed handpiece. Friction plasticizes gutta-percha.Titanium core may be severed and left or removed while still spin-ning. (Courtesy of J.S. Dental Mfg. Co.)

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19.1˚C rise in temperature because it took 141 secondsto plasticize the mass. They felt the heat generated bythe Cavitron would not be harmful.441

At the University of Iowa, on the other hand, a groupwas quite impressed with a technique using an Enacultrasonic unit (Osada) with an attached spreader.Unlike the University of Texas group, however, they didnot attempt to plasticize the gutta-percha. They felt thespreader more easily penetrated the mass of gutta-per-cha than did the finger spreaders, and that in the end,the energized spreading technique led to a morehomogeneous compaction of gutta-percha with lessstress and less apical microleakage442 (Figure 11-70).

Thermoplasticized Injectable Gutta-percha Obtur-ation. An innovative device, introduced to the profes-sion in 1977, immediately caught the fancy of dentistsinterested in the compaction of warm gutta-percha.Developed by a group at Harvard/Forsyth Institute,gutta-percha was ejected out of a prototype pressuresyringe that had warmed it to 160˚C. At this temperature,the gutta-percha would flow through an 18-gauge nee-dle.443 From this early model, a more efficient system wasdeveloped and patented.444,445 Today, through furtherimprovements, the device is marketed as the Obtura IIHeated Gutta-Percha System (Obtura-Spartan Corp.,Fulton; Mo.) (Figure 11-71), with digitally controlled tem-peratures ranging from 160˚C to 200˚C while the needle

size has been reduced to either 20 gauge (equal to a size 60file) or 23 gauge (equal to a size 40 file) (Figure 11-72).

Although regular beta-phase gutta-percha is stillused, the clinician can now choose a less viscous, high-er flow form of gutta-percha known as Easy Flow(Charles B. Schwed Co.; Kew Gardens, N.Y.).

Gutmann and Rakusin, leading proponents ofthermoplasticized gutta-percha obturation, haveemphasized the importance of properly preparingthe canal to receive the injection needle and com-pacting the warm gutta-percha. They point out theimportance of preparing a “continuously taperingfunnel from the apical matrix to the canal orifice.”446

They especially note the significance of properlyshaping the transitional area from the apical third tothe middle third, particularly in curved canals(Figure 11-73), and warn against the development ofthe “coke-bottle” canals so frequently seen followingGates-Glidden canal preparations (Figure 11-74).The tapered preparation enhances the flow of theplasticized material, whereas the Coke-bottle prepa-ration negates the flow.446

A definitive apical matrix is also important. Thisconstriction prevents the extrusion of filling materialinto the periapex (see Figure 11-73). Preparations tosize 25 or 30 files at the apical terminus, tapered to asize 60 file at the coronal orifice, have proven perfectly

Obturation of the Radicular Space 629

Figure 11-70 Comparison in obturation between hand-lateral compaction and ultrasonic compaction. Left, Accessory point folded incanal during lateral compaction following finger spreading. G, individual gutta-percha points. C, canal wall. High power (×320 original mag-nification). Center, Gutta-percha compacted by Enac ultrasonic spreader tips (no fluid coolant.) Note uniformity of gutta-percha mass withonly two “crevice marks” (A). C denotes canal walls. High power (×320 original magnification). Right, Low power (×10 original magnifica-tion) of apical third obturation by ultrasonic. B marks well-filled foramen. Rectangular area is seen at high power in center panel. Reproducedwith permission from Baumgardner KR and Krell KV.442

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adequate as long as there is sufficient blending of thecoronal preparation with the apical preparation.

Methods of Use. Although initially it was hopedthat the “gutta-percha gun” could be used to totallyobturate the canal, it soon became apparent that sealerand further compaction were necessary. Sealer servesits usual role of filling the microscopic interfacebetween the dentin and gutta-percha as well as actingas a lubricant. Compaction became necessary to closespaces and gaps while forcing the gutta-percha lateral-ly and vertically. It also compensates for shrinkage asthe gutta-percha cools. Furthermore, the smallest injec-tion needle, 23 gauge, was too large to reach the apex inmost cases.

630 Endodontics

Initially, a technique was developed of depositingthe warm plasticized gutta-percha well down into thecanal and then compacting it with hand or finger plug-gers to the apical terminus. In using this method, how-ever, one must be prepared to act as soon as thegutta-percha is placed because it cools rapidly andhardens, often within 1 minute; however, the Easy Flowgutta-percha does afford at least 10 to 15 more secondsof working time.

Figure 11-71 Obtura II delivery sys-tem. Panel has temperature controland digital temperature display indegrees Celsius. The pistol-grip syringe(right) extrudes plasticized beta-phasegutta-percha through flexible needle.Technique VHS is included. (Courtesyof Obtura/Spartan USA.)

Figure 11-72 Warm plasticized gutta-percha stream extrudedthrough needle tip (arrow) of Obtura II. (Courtesy ofObtura/Spartan USA.)

Figure 11-73 Gutmann insists that the most critical area of canalpreparation is the transition from the apical third to the middlethird of the canal. Reproduced with permission from Gutmann JLand Rakusin H.446

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The injection needle and pluggers must have beenpreviously tried for size in the canal. Although themanufacturer recommends that they should reachwithin 3.5 to 5 mm of the terminus and fit loosely atthat point, sufficient compaction can still occur aslong as the needle reaches halfway between the canalorifice and apical terminus in a well-prepared canal. Infact, Lambrianidis and coworkers in 1990 demonstrat-ed that there was no statistically significant differencein linear dye leakage in Obtura-filled canals in whichthere were varying distances of the needle tip from theapical foramen during obturation.447 Regardless ofwhether a sectional technique is used or a completefilling method is used, silicone stops are placed onpluggers of adequate diameter to ensure they willmove and compact the softened material and not just“pierce” through it.

A light liner of a slow-setting sealer is placed into thedried canal to the prechosen depth short of the apex.Excessive sealer causes pooling and should be avoided.Sealers such as Roth’s 801, AH Plus, or Sealapex arerecommended. This is followed by the Obtura needle,and a deposit of gutta-percha is made. The canal maybe totally filled as the needle is withdrawn, or a small

deposit may be made and compacted with the inten-tion of filling the canal segmentally.

Research by Johnson and Bond at Louisiana StateUniversity showed no difference in dye penetration incanals that were backfilled with 1 mm, 4 to 5 mm, or 10mm increments irrespective of whether Roth’s 801 orAH26 sealer was used.448 However, the clinician proba-bly has better control of moving and compacting gutta-percha when segmental filling is done.

Once the deposit is placed, the premeasured plugger israpidly used to move the gutta-percha apically and later-ally. A drop of sealer on the tip of the plugger will pre-vent its adhering to the gutta-percha. When one is satis-fied that the apical third is obturated, a quick radiographor digital image can be made to ensure the placement.Once viewed, the obturation may be completed.

If the filling is short, gutta-percha, if now firm, maybe warmed with a hot instrument and then furthercompacted; the bolus may also be completely removedand the canal refilled. In this event, one may warm thetip of a Hedstroem file, insert it into the gutta-percha,let it cool for 1 minute, and then remove the bolus ofgutta-percha. Refilling of the canal can then be done,this time inserting the pluggers to a greater depth,using Easy Flow gutta-percha and/or repreparing thecanal first. The radiograph of the final result shouldshow a thoroughly compacted, totally obturated reflec-tion of the tapered canal preparation (Figure 11-75).

Obturation of the Radicular Space 631

Figure 11-74 Excessive preparation with Gates-Glidden burs orPeeso reamers creates rapid tapering. The “Coke-bottle effect” ofthe canal negates efficient flow of plasticized gutta-percha.Reproduced with permission from Gutmann JL and Rakusin H.446

Figure 11-75 Ideal tapered preparation for any obturation tech-nique, particularly syringe delivery of plasticized gutta-percha.Reproduced with permission from Gutmann JL and Rakusin H.446

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Another popular obturation method used by manyendodontists is to initially place a fitted master point tothe apical terminus and follow this with the Obturaneedle-tip, depositing a bolus of warm gutta-perchaaround the point. This is immediately compacted ver-tically and laterally. More plasticized gutta-percha isthen added and compacted. This technique will betterensure apical closure without overfilling.

Success with any of these techniques is operatordependent. Repeated practice on plastic-block canals aswell as extracted teeth is imperative. To gain intraoralexperience, one might start by using the device to back-fill other methods before tackling full-treatment casesand by initially using the system on large, relativelystraight canals. As a matter of interest, the Obtura II isprobably being used more frequently as a backfillingdevice than for primary obturation.

Efficacy and Safety of the Thermaplastic InjectableGutta-Percha Technique. A number of studies on theheat generated by this method have been done.Gutmann et al. found in vitro that the gutta-perchaemerged from the needle at 71.2˚C in a body tempera-ture environment.449

In an in vivo study on dogs, the mean intracanaltemperature of the gutta-percha was 63.7oC.Maximum temperature elevation on the bone overly-

632 Endodontics

ing these test teeth was only 1.1˚C over 60 seconds. Thisappears to be a safe temperature level.450

Others recorded much higher (137.81˚C) intracanalrecordings.451 Hardie recorded a temperature rise of9.65˚C on the external surface of a tooth.452 Thisdropped to 4.75˚C in 3 minutes and compared with a15.38˚C rise in temperature generated by an EnginePlugger compactor spinning at 8,000 rpm.452 Boneinjury has been reported with external root tempera-ture rises of 10˚C if maintained for 1 minute.453

Hardie’s reported 9.65˚C increase (dropping to 8.20˚Cin 1 minute) appears to fall within safe limits.452 Wellerand Koch evaluated external root temperatures in vitrowhen using gutta-percha thermoplasticized at 200˚Cand additionally found that the rise in temperature waswell below the critical level of 10˚C.454

The efficacy of thermoplasticized gutta-percha infilling fins and cul-de-sacs,455 internal resorption cavi-ties,456,457 “C”-shaped canals, accessory canals, andarborized foramina is well documented (Figure 11-76).All researchers insist, however, that sealer is necessaryto prevent microleakage.347,458 Clinical success rateswith the injection technique have been reported at93.1%.459

Compared with other techniques, the thermoplasti-cized, regular beta-phase (higher heat) gutta-percha

Figure 11-76 Use of the Obtura II in obturating enormouscanals. A, Filling following apexification. Open foramen denotesnecessity of obturation. B, C-shaped canal with trident foramina(arrow). (A courtesy of John G. Schoeffel.) B reproduced withpermission from Serota KS. Oral Health 1989;79:35.

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proved equal to laterally compacted cold gutta-perchain a number of studies of microleakage362–364 and sig-nificantly poorer in others.347,348 Virtually all of thestudies reported some overfilling and apical extru-sions.347,348,362,363 At least one author admitted, how-ever, that his group’s results “confirmed the opinion ofGutmann and Rakusin that clinicians should take timeto master the technique before employing it in thetreatment of their patients.”347 As with any obturationtechnique, the efficacy and long-term success of themethod are highly dependent on the cleaning andshaping of the canal and the resultant degree of reten-tion and resistance form that is developed.

Inject-R Fill–Backfilling Technique. As stated earli-er, the Obtura II is frequently used in “backfilling,” amethod for completing total canal obturation after theapical third of the canal has been filled. Anothermethod of backfilling has been developed by Roane atthe University of Oklahoma and is marketed as Inject-R Fill (Moyco-Union Broach; Bethpage, N.Y.).

Inject-R Fill, a miniature-sized metal tube contain-ing conventional gutta-percha and plunger, simplifieswarmed vertical compaction by altering the backfillingprocess. The technique allows for delivery of a singlebackfill injection of gutta-percha once the apical seg-ment of a canal has been obturated (Figure 11-77).

The apical segment of the canal can be obturatedusing any technique including lateral compaction, tra-ditional warm vertical compaction, or System B. If acold lateral technique is used, the cones of gutta-perchaextruding from the canal must first be heat severed at asufficient depth so a plugger can be used to compactthe remaining heat-softened segment in the apical

third of the canal. If the System B or vertical com-paction is used, the method already results in an api-cally compacted segment.

According to the Inject-R Fill technique, the coronalwalls must be resealed with sealer prior to filling theregion with gutta-percha from the device.460 TheInject-R Fill must first be heated in a flame or an elec-tronic heater and the coronal surface of the gutta-per-cha already in the canal should be warmed using aheated instrument. When a burner is used, the stainlesssteel gutta-percha filled sleeve is waved through theflame until gutta-percha begins to extrude from theopen end. The warmed unit is then placed into the ori-fice of the canal. For the device to fit, the canal orificemust be at least 2 mm in diameter. A push of the han-dle toward the canal injects the heated gutta-perchainto the canal. The carrier is then rotated to break itfree from the access.

Prefitted hand or finger pluggers are subsequentlyused to compact the gutta-percha and push the inject-ed mass into contact with the apical segment. The plug-ger must be positioned in the center of the mass andpressed firmly toward the apex. Pressure is sustainedfor a few seconds before the plugger is rocked from sideto side and rotated to break it free. As the plugger isremoved, a small void is left in the center of the mass.The void is closed by folding over remaining gutta-per-cha from the sides and packing it apically. This processis repeated until a larger plugger can be used withoutcreating a void and the gutta-percha mass is firm.Coating the tip of each Inject-R Fill with sealer beforeplacing it in the canal will prevent sticking of the gutta-percha and should enhance the gutta-percha/sealer/canal interface. According to Roane, the tech-nique is rapid and produces a result similar to that ofwarm vertical compaction (personal communicaton,April 2000).

An important caveat must be issued, warning any-one using a system of injection, thermoplasticizedgutta-percha—be very careful not to force or overin-ject the heat-softened material.461 Disastrous resultsmay develop if, for example, the softened gutta-perchais injected into the maxillary sinus or the inferior alve-olar canal (Figure 11-78).

SOLID-CORE CARRIER: MANUAL INSERTION

ThermaFil (Dentsply/Tulsa)Densfil (Dentsply/Maillefer),

Soft-Core (Soft-Core System, Inc.), and Three Dee GP (Deproco UK Ltd.)

In 1978, Johnson described a unique yet simplemethod of canal obturation with thermoplasticized

Obturation of the Radicular Space 633

Figure 11-77 Inject-R-Fill shows protrusion of heat-softenedgutta-percha prior to its insertion into the canal. (Courtesy ofMoyco/Union Broach Co.)

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alpha-phase gutta-percha carried into the canal on anendodontic file.462 What was a curiosity in 1978 hasbecome today a popular and respected technique ofcanal obturation (Figure 11-79). ThermaFil is consid-ered the major core-carrier technique, and through alicensing agreement with Dentsply, a duplicate prod-uct, Densfil was created. Recently, two similar productswere introduced: Soft-Core, and its European version,Three Dee GP.

634 Endodontics

“ThermaFil is a patented endodontic obturator con-sisting of a flexible central carrier, sized and tapered tomatch variable tapered files (.04/.06) endodontic files.The central carrier is uniformly coated with a layer ofrefined and tested alpha-phase gutta-percha.”463 Theuse of the variable tapered files in canal preparation hasenhanced the fit, placement, movement, and com-paction of the gutta-percha delivered by the ThermaFilcore carrier. Likewise, the ThermaFil system now

Figure 11-78 A, Plasticized gutta-percha extruded from syringe overfills enormous area of mandible. B, Pathologic specimen ofosteomyelitic bone and chronic inflammation attached to extruded gutta-percha. Reproduced with permission from Gatot A et al.461

Figure 11-79 A, Original handmade gutta-percha obturator mounted on regular endodontic file. B, Modern manufactured ThermafilObturators—alpha-phase gutta-percha mounted on radiopaque, flexible, plastic carriers. Note silicone stop attachments. A reproduced withpermission from Johnson WB.462 (B courtesy of Dentsply/Tulsa Dental Products.)

A B

A B

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comes with metallic size verifiers that are used todetermine, with greater precision, the size and shape ofthe prepared canal prior to choosing the correctThermaFil carrier.

Initially, the central carrier was a newly designedstainless steel device. Contemporary carriers are madeof radiopaque plastic that is grooved along 60 degreesof their circumference (Figure 11-80). While thegutta-percha covering the original carriers was heatedin a flame, the new plastic core carriers are heated in acontrolled oven environment called the ThermaPrepPlus heating system (Dentsply/Tulsa; Tulsa, Okla.)(Figure 11-81). The heating time is well delineated andis dependent on the size of the core carrier. The use ofthe oven, according to the manufacturer’s directions, isessential for success with this technique.

Soft-Core, or its counterpart, Three Dee GP, is sim-ilar to ThermaFil; however, it contains a bipolymercompound and a tungsten core that is radiopaque. Ithas an easily detachable handle, referred to as a metal-lic insertion pin, that is removed with a slight twistingaction. This leaves the coronal portion of the plasticcore hollow, thus facilitating postspace preparation.The presence of the metallic insertion pin also allows acurving of the coronal portion of the carrier, thus facil-itating the angle of core insertion. It is supplied in asterile blister pack that also contains a matching sizeverifier. The carriers are thinner in taper than theThermaFil carriers but are ISO sized at the apex. Thiswas done to facilitate their use in small canals that aredifficult to shape. Heating of the gutta-percha on theSoft-Core carrier is done in a halogen oven that is ther-mostatically controlled.

Method of Use. The detailed use of the core carrierobturation technique has evolved after years of develop-ment and clinical use.464 Careful cleaning and shaping ofthe canal are essential, as is the development of a contin-uously tapering preparation. Contemporary dictatesfavor the use of the variable tapered endodontic files toachieve this goal and to enhance the obturation affordedby the ThermaFil technique.

Prior to obturation, it is recommended that the smearlayer be removed with the appropriate agents. This willpromote the movement of the softened material into thedentinal tubules and enhance the seal.465 After the canalis dried, a very light coat of sealer is applied to all of thewalls. It acts as an adhesive as well as a lubricant.Preferred sealers include Thermaseal (Dentsply/Tulsa;Tulsa, Okla), AH-Plus (Dentsply/Maillefer; Tulsa, Okla.),Sealapex (Kerr/Analytic; Orange, Calif.), or ZOEcements. Quick-setting cements such as Tubliseal, orcements that contain natural gutta-percha softeners, such

as Sealex or CRCS, should be avoided with this tech-nique. In the case of the former, the sealer sets up too rap-idly when warmed. In the case of the latter, the chemicalsoftening of the gutta-percha makes it too tacky andadherent to the dentin walls, thereby reducing its flowapically and into the canal irregularities.

Immediately after the sealer is applied, the warmedobturator is removed from the ThermaPrep Plus heaterand carried slowly to full working length in the canal.

Obturation of the Radicular Space 635

Figure 11-80 Details of the anatomy of the Thermafil plasticCarrier. The core is grooved to allow for the release of trapped airduring the placement of the carrier. Note also the circular millime-ter markings above the grooved area that facilitate length placementof the carrier. (Courtesy of Dentsply/Tulsa Dental Products.)

Figure 11-81 ThermaPrep Plus oven ensures proper softening ofThermafil Obturators within seconds. (Courtesy of Dentsply/TulsaDental Products.)

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Previously, the built-in rubber stop, on the calibratedshaft, had been set at the proper length position. The car-rier is not twisted during placement, and attempts toreposition the carrier should be avoided to prevent dis-ruption of the gutta-percha that was initially positionedthrough the compacting action of the core carrier.

Once it is ensured radiographically that the canalhas been filled to the desired position, the shaft is sev-ered in the coronal cavity. While the handle is firmlyheld aside, a No. 37 inverted cone bur is used to trim offthe shaft 2 mm above the coronal orifice. Specific burshave also been developed for this task: Prepi Bur(Prepost Preparation Instrument) (Dentsply/Tulsa;Tulsa, Okla.). The Prepi Bur, a noncutting metal ball, isrun in a handpiece and is also used to create postspacesafely and efficiently when needed. This space can becreated immediately or on a delayed basis withoutaltering the apical seal.466

Johnson has suggested that the final compaction canbe improved if a 4 to 5 mm piece of a regular gutta-per-cha cone is inserted into the softened gutta-percha andcompacted apically and laterally with a large plugger. 464

Gutta-percha accessory points can also be used in a sim-ilar fashion to achieve a greater depth of material deliv-ery if the canal is very wide buccolingually. In this case,an appropriately sized spreader would be used to com-pact the cones into the softened mass. The use of warminjected gutta-percha by Obtura (Obtura/ Spartan,USA) is also an accepted technique to add sufficientbulk to the obturating material. The gutta-perchareaches its final set in 2 to 4 minutes.

THERMAFIL SAFETY

Saw and Messer from Australia evaluated and com-pared the root strains associated with the compactionof gutta-percha delivered from the Obtura andThermaFil with lateral compaction.467 The ThermaFiltechnique required only minimal compaction that waslimited to the coronal end of the carrier. Therefore,with this technique there was significantly less strainduring delivery and compaction than there was withthe other tested techniques.

An apical stop or definitive apical constriction mustbe present to prevent movement of the gutta-perchaand/or the plastic core from extending beyond the rootcanal. Often, a small puff of sealer or gutta-percha willbe extruded.464 A US Army group found thatThermaFil was more apt to extrude through a patentapical foramen than was Obtura, Ultrafil, or warm lat-eral compaction (Endotec). On the other hand, if adentin “plug” was present at the apical orifice,ThermaFil was less apt to extrude than were the oth-

636 Endodontics

ers.468 The use of the size verifiers in choosing the cor-rectly sized core carrier has also reduced the incidenceof material overextension.

The precurving of ThermaFil obturators is usuallynot necessary if the canal is prepared properly, as theflexible carrier will easily move around curves. Withthis technique, gutta-percha will flow easily into canalirregularities such as fins, anastomoses, lateral canals,and resorptive cavities464,469 (Figure 11-82).

Efficacy of ThermaFil Obturation. A nationallyrecognized evaluator of materials, devices, and tech-niques, Clinical Research Associates (CRA), headed byChristensen, has indicated that “ThermaFil allows sim-ple, fast, predictable filling of root canals. It was foundto be especially useful for small or very curvedcanals.”470 Radiographic assessment of this gutta-per-cha delivery technique has been quite favorable,468 andrecent adaptation studies that have looked at the con-temporary use of the technique have found it compa-rable to, if not better than, lateral compaction.469,471

Gutmann et al. and W. P. and E. M. Saunders fromGlasgow evaluated ThermaFil versus lateral compactionin a series of studies.469,471 They reported that“ThermaFil resulted in more dense and well adaptedroot canal fillings throughout the entire canal systemthan lateral condensation with standard gutta-percha.”Both techniques “demonstrated acceptable root canalfillings in the apical one-third of the canal.” Similarexcellent adaptation was observed when comparingThermaFil with the System B technique.472 However,the gutta-percha from the ThermaFil carrier did show agreater propensity to extrude beyond the apex.469,472

Wolcott and coworkers, in an in vitro study atTennessee, found that the movement of ThermaFilgutta-percha and sealer into lateral canals was compa-rable to lateral compaction; however, the ThermaFilwas more effective in the main canal.473 Weller et al. atGeorgia used a split-tooth model to assess gutta-perchaadaptation using Obtura, three types of ThermaFil corecarriers, and lateral compaction.474 No root canal seal-er was used. The best adaptation was with Obturaobturations, followed by ThermaFil plastic, ThermaFiltitanium, ThermaFil stainless steel, and lateral com-paction. Of interest in this study was the lack of apicalextrusion noted with the ThermaFil obturations.

In assessing leakage patterns with the contemporaryThermaFil technique, Gutmann and W. P. and E. M.Saunders found initially “no significant differences inleakage between the techniques.”469 At 3 to 5 months,however, both techniques revealed apical microleakage.On the other hand, “ThermaFil obturations demon-strated greater adaptation to the intricacies of the canal

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system.”469 Fabra-Campos reported much the samefrom Spain.475 Using plastic-carrier ThermaFil and lat-eral compaction, Pathomvanich and Edmunds fromWales used four different leakage methods and foundno difference in the leakage patterns with any of theevaluative techniques, nor was there any differencebetween lateral compaction and ThermaFil.476 Valliand coworkers compared Densfil (Thermafil look-a-like) obturations with lateral compaction in canals thatwere prepared with hand instruments.477 While theDensfil obturations showed less mean apical leakage(1.39 mm) than lateral compaction (2.76 mm), thedata were not significant. Similarily, they also com-pared the coronal leakage with both techniques, withthe mean coronal leakage for Densfil being 2.87 mmand the mean coronal leakage for the lateral com-paction being 4.028 mm, but no statistically significantdifferences were noted.

Most recently, both short- and long-term leakagecomparing ThermaFil with System B in the absence ofthe smear layer was reported by Kytridou et al.472 Therewere no significant differences in the short-term leak-age patterns (10 and 24 days); however, leakage at 67days was greater in the ThermaFil group. Unlike otherstudies, however, these specimens were stored in HanksBalanced Salt Solution to better simulate the periradic-ular tissue fluid environment.

Silver Point Technique. Another solid-core mate-rial of long standing (but not in good standing) is thesilver point technique. Despite nearly universal disap-probation, there are uses for silver points.

The fault lies not in the point but in the execution.The cavity prepared to receive the point must be asperfectly rounded and tapered as the point itself. “Itmust fit like a cork in a bottle.” Too often, round silverpoints are cemented into ovoid canals. Over the years,as the sealer surrounding the point gradually dissolvesaway, microleakage and a subsequent periradicularlesion develop.

With all of the other techniques available, why usesilver points at all? They are very easy to use in narrowcanals. They are rigid, yet flexible, and can be posi-tioned rapidly. Ingle has pointed out that “…Whenproperly cemented to place, they provide a perfectlyadequate filling for the geriatric patient at a real timesaving.”478 He further noted that the very elderly have alimited life expectancy, and that silver points, evenimproperly done, have been known to last over 20years. Treatment for a 75-year-old patient may besomewhat different than that for a 25-year-old patient.

Furthermore, secondary dentin formation narrowsthe canal lumen in “ancient’’ teeth, lending them topreparation by reaming. “Good candidates would bethe straight round canals in upper central incisors, or

Obturation of the Radicular Space 637

Figure 11-82 Obturation with Thermafil. A, Central incisor filled withsize 60 Thermafil Obturator—plastic carrier. Note lateral canal nearapex. B, Both mesial and distal canals filled with size 45 ThermafilObturators—plastic carrier. Note apical fill and lateral canal. (Courtesyof Dr. W. Ben Johnson.)

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the two canals in upper first premolars, or a straightpalatal canal in an upper first molar, or a straight distalcanal of a lower first molar. Occasionally, even buccalcanals in upper molars, upper canines, or mesial canalsin lower molars qualify if they are straight.”478

These might well be cases in which the final apical prepa-ration can best be done with one of the new reamer-typeinstruments: the Handy-Gates (Dentsply/Maillefer; Tulsa,Okla. and Switzerland) or the LightSpeed (LightSpeedTech., Inc.; San Antonio, Tex.). In any event,“the silver pointbaby need not be thrown out with the bath.”

APICAL THIRD FILLING

SimpliFill Obturation Technique

SimpliFill is a relatively new, two-phased obturationmethod that advocates the use of a stainless steel carri-er to place and compact a 5 mm segment of gutta-per-cha into the apical portion of a canal (Figure 11-83).Once placed, the carrier is removed, leaving a plug ofgutta-percha. If a post is not desired, the second phaseuses a specially designed syringe to backfill the remain-der of the canal with Ketac-Endo sealer along withaccessory cones of gutta-percha. The clinician can alsochoose any other method to backfill the remaining por-tion of the canal. According to the manufacturer, theoverall advantages of SimpliFill are that its use helpsconserves dentin because of the Lightspeed instrumen-tation technique (less flaring); it eliminates additionalinternal forces since no spreader or plugger is used tocompact the apical plug; it is simple to master; and, incontrast to other core-carrier systems, no carrier is leftin the canal.

638 Endodontics

SimpliFill was originally developed by Senia atLightspeed Technology to complement the canal shapecreated using Lightspeed instruments. The Apical GPPlug size is the same ISO size as the Lightspeed “MasterApical Rotary” (MAR) (see Chapter 10).

Following the completion of canal preparation usingrotary Lightspeed, the specially designed Apical GPPlug Carrier corresponding to the MAR is trial fittedwithout sealer into the dry canal. Before insertion,however, the rubber stopper on the carrier, with itsattached gutta-percha, is set 2 mm short of the workinglength. The carrier is then inserted into the canal andslowly advanced, until it should start to bind at thelength indicated by the rubber stop (ie, 2 mm short ofthe working length). Once the fit has been verified, theApical Plug carrier is removed and the canal is coatedwith an appropriate sealer using the MAR or a sealersaturated paper point. The rubber stopper on the carri-er is now advanced 2 mm to the working length. TheGP Plug is subsequently coated with sealer, inserted inthe canal, and advanced until resistance is felt, about 2mm short of the working length. Using the carrier, theGP Plug is now vertically compacted to the workinglength with firm apical pressure. The carrier must notbe rotated during insertion or compaction. Once theGP Plug is snugly fit, the GP Plug is released by rotat-ing the carrier handle counterclockwise. During thisrotation, the carrier must not be pushed or pulled. Ifthe GP Plug does not release, the carrier sleeve isgrasped with cotton pliers and, while pushing apicallyon the sleeve, the handle of the carrier is rotated coun-terclockwise and withdrawn.

Phase two consists of backfilling the remaining canalif no post is desired. The clinician has a number ofoptions for backfilling, including the method advocat-ed by the manufacturer described as follows. ASimpliFill syringe is loaded with a sealer such as Ketac-Endo and the sealer is slowly injected into the canalspace as the tip of the needle, equivalent to size #40 file,contacts the GP Plug and is slowly withdrawn.Inserting the needle all the way to the top of the plugwill help eliminate formation of air bubbles during thebackfill. An ISO standardized gutta-percha cone, equiv-alent in size to the Apical GP Plug used to fill the apicalsegment, is then coated with sealer and placed into thesealer-filled canal until it contacts the compacted GPPlug. Accessory gutta-percha cones can be added asspace fillers. As stated earlier, the clinician can alsobackfill using traditional warm-vertical compaction ormay simply backfill using the Obtura II.

Since the technique is so new, there was only onepublished study. In 1999, Santos and coworkers at the

Figure 11-83 SimpliFill apical gutta-percha plug. Point is lightlyheated and used as primary apical fill. Carrier is twisted for removaland used as plugger. (Courtesy of LightSpeed Technol.)

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University of Texas at San Antonio evaluated the proto-type sectional method (SimpliFill) and compared it tolaterally compacted gutta-percha.479 In their study, sin-gle canal teeth were prepared using Lightspeed andwere subsequently obturated using three methods: lat-eral gutta-percho compaction with Ketac-Endo sealer,lateral compaction with Roth’s 801 sealer, or theSimpliFill sectional method with Ketac-Endo sealer fol-lowed by a single cone of gutta-percha in Ketac-Endosealer as backfill. Using India ink to measure leakage,they found no statistically significant difference in api-cal microleakage among the three groups. In addition,it was noted that the sectional method was significant-ly faster than lateral compaction.479 Although the tech-nique appears promising, further studies will be neces-sary along with clinical trials to determine the long-term efficacy of the SimpliFill system.

Dentin Chip Apical Filling. A method findingincreasing favor, and one that inadvertently happensmore often than not, is the apical dentin chip plug,against which other materials are then compacted.Quite probably, some of the so-called “miraculouscures” occur apically, to prepared but unfilled canals,because the apical foramens have actually been obtu-rated by dentin chips from the preparation.480 To do

this deliberately constitutes the “new technique,” a“biologic seal” rather than a mechanochemical seal.

The premise that dentin filings will stimulate osteoor cementogenesis is well founded. Gottlieb and Orbannoted cementum forming around dentin chips in thePDL as early as 1921. The German literature is repletewith this method. Mayer and Ketterl filled 1,300 canalswith apical dentin chips and reported 91% success.481

Ketterl later reported 95% success with cementum-likeclosure at the apex.482 Waechter and Pritz also reported“osteocementum” apical closing in 20 human cases.483

Baume et al. described “osteodentin” closings butincomplete calcification across all of their histologicserial sections.484

More often than not, dentin chip obturation undoubt-edly prevents overfilling. El Deeb et al. found exactly that:“The presence of the apical dentinal plug,” they stated,“was significantly effective in confining the irrigatingsolutions and filling materials to the canal space.”485

This same conclusion was reached by Oswald et al.,who observed that dentin chips lead to quicker healing,minimal inflammation, and apical cementum deposi-tion, even when the apex is perforated486 (Figure 11-84). Holland et al., from Sao Paulo, found, however,that dentin chips, if infected, are a serious deterrent to

Obturation of the Radicular Space 639

Figure 11-84 Dentin chip root canal plug after 3 months. Left, Periradicular area. B, bone, C, cementum, DP, dentin plug. Arrows indicatecanal wall. Right, High-power view of same periradicular area. C, cementum within canal around dentin chips (arrows). OB, new bone cells.Reproduced with permission from Oswald RJ and Friedman CE.486

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healing,487 and Torneck et al. found that some dentinchips may actually irritate and hinder repair.488

Method of Use. The dentin chip technique hasbeen used and taught at the Universities of Oregon andWashington (J. Marshall, personal communication,July 26, 1981; G. Harrington, personal communication,August 13, 1982). After the canal is totally débrided andshaped and the dentin no longer “contaminated,” aGates-Glidden drill or Hedstroem file is used to pro-duce dentin powder in the central position of the canal(Figure 11-85, A). These dentin chips may then bepushed apically with the butt end (Figure 11-85, B) andthen the blunted tip of a paper point (Figure 11-85, C).They are finally packed into place at the apex using apremeasured file one size larger than the last apicalenlarging instrument489(Figure 11-85, D). One to 2mm of chips should block the foramen (G. Harrington,personal communication, August 13, 1982).Completeness of density is tested by resistance to per-foration by a No. 15 or 20 file. The final gutta-perchaobturation is then compacted against the plug (Figure11-86).

Japanese researchers found they could totally pre-vent apical microleakage if they injected 0.02 mL ofClearfil New Bond dentin adhesive (J. Morita, Japan)into the coronal half of the dentinal apical plug.490

Harrington points out that a dentin plug is de rigueurif the apical foramen is perforated or open for any rea-son (G. Harrington, personal communication, August13, 1982). In flaring the wall to produce dentin chips,care must be taken not to thin the walls excessively.

Efficacy of Dentin Chip Apical Obturation. Asstated earlier, one of the positive effects of a dentin plug

640 Endodontics

filling is the elimination of extrusion of sealer orgutta-percha through the apex. This reduces periradic-ular inflammation.486 It also provides an apical matrixagainst which gutta-percha is compacted.442,491 Thegroup at the University of Connecticut found, howev-er, that they could not totally block the apical foramenwith chips following vital pulpectomy in baboons.492

On the other hand, they did report “…hard tissue for-mation was common but no total closure occurred,”and that “…tissue response to dentin chips was gener-ally favorable.”492

In a monkey study at Indiana University, no attemptwas made either to form or avoid forming a dentinplug. It was found, however, that 77% of 43 cases haddemonstrable plugs. It was further reported that teethwith plugs “had a significantly lower frequency of[periradicular] inflammation than teeth without plugs(p = 0.02).” Although not a consistent finding, “newcementum was observed adjacent to dentin filings”493

(Figure 11-87). However, in this experiment, the dentinplugs were not purposely produced. Also, residual pulptissue was sometimes present.

Another monkey study done at Loma LindaUniversity indicated that the inorganic component ofdentin, hydroxyapatite, is evidently the principal stim-ulant in producing more hard tissue formation and lessinflammation than are fresh dentin chips or deminer-alized dentin.494

Figure 11-85 Dentin chip–apical plug filling. A, Clean dentinchips produced in midcanal with Gates-Glidden drill. B, Loosechips collected and moved apically with butt end of paper point. C,Dentin chips compacted at apical foramen with blunted paperpoint. D, Final compaction with file, one size larger than last enlarg-ing instrument. Redrawn from Oregon Health Sciences University.Laboratory manual. Portland (OR): Oregon Health SciencesUniversity; 1980.

Figure 11-86 Dentin chips compacted into last 2 mm of prepara-tion, spilling over from true working length (TWL) to stimulatecementogenesis. Gutta-percha and sealer complete obturation.Redrawn from Oregon Health Sciences University. Laboratorymanual. Portland (OR): Oregon Health Sciences University; 1980.

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After previously noting that infected dentin chipshindered periradicular healing,487 Holland et al. com-pared the cementogenesis and inflammation betweendentin chips and calcium hydroxide. They found thatdentin chips were responsible for thicker cementumformation but that overall there was no discernible dif-ference between the two materials in ferrets.495

The group at the University of Washington, in asmaller study, found that “the dentin plugs were morecomplete than those observed with calcium hydroxide.”No inflammation was present after 1 month. Bothmaterials worked equally well to control the extrusionof the filling material; however, the calcium hydroxidetended to wash out quickly.496

Returning to the original German studies,423–425

through the reports by Erasquin in 1972497 andTronstad in 1978,498 and including more recentreports,490–496 one must conclude that the dentin chipapical plug is a valuable contribution to endodonticsuccess and deserves to be more widely used.

Calcium Hydroxide Apical Filling. Cementogenesis,which is stimulated by dentin filings, appears to be repli-cated by calcium hydroxide as well499–506 (Figure 11-88).Dentists have long observed the dramatic repair thatoccurs at the apex of a wide open canal of a tooth whosepulp was destroyed by trauma. Removing the necroticcanal contents and bacterial flora, thoroughly débriding

Obturation of the Radicular Space 641

Figure 11-87 Dentin plug-induced cemental formation. Band ofcementum (C) is seen adjacent to dentin plug (P). Periodontal lig-ament (L) is normal. Reproduced with permission from PattersonSM et al.493

Figure 11-88 Periradicular repair following intracanal application of calcium hydroxide. A, Low-power view of periapex. Acute inflammatoryresorption of dentin and cementum following pulpectomy. Canal filled with calcium hydroxide mixture (CH). New hard tissue forming acrossapex in response to Ca(OH)2. B, Higher-power view of repair leading to apical “cap” (arrow). (Courtesy of Dr. Billie Gail Jeansonne.)

A B

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the dentin walls, disinfecting the space, and totally fillingthe canal with calcium hydroxide, will practically ensureapexification (Figure 11-89). The same phenomenonapplies to the closed apex—cementification reacting tothe placement of a plug of calcium hydroxide. This isalso the theory behind the calcium hydroxide–contain-ing sealers that appear to be better in theory than inpractice.507

642 Endodontics

As noted previously, calcium hydroxide resorbs awayfrom the apex faster than do dentin chips.496 However,Pissiotis and Spångberg noted that calcium hydroxidemixed with saline resorbed but was replaced by bone inmandible implant studies.508

Method of Use. Calcium hydroxide can be placedas an apical plug in either a dry or moist state. Dry cal-cium hydroxide powder may be deposited in the coro-

Figure 11-89 Apexification of pulpless incisor with periradicular lesion. A, Preoperative film. B, Calcium hydroxide and camphoratedmonochlorophenol filling canal and extruding through apex. C, Nine months later, canal filled with sealer, softened gutta-percha, and heavyvertical compaction. No overfilling. D, Two-year recall. (Courtesy of Dr. Raymond G. Luebke.)

A B

C D

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nal orifice from a sterilized amalgam carrier. The bolusmay then be forced apically with a premeasured plug-ger and tapped to place with the last size apical file thatwas used. One to 2 mm must be well condensed toblock the foramen. Blockage should be tested with a filethat is one size smaller.

Moist calcium hydroxide can be placed in a numberof ways: as described earlier with amalgam carrier andplugger, with a Lentulo spiral, or by injection from oneof the commercial syringes loaded with calciumhydroxide: Calasept (J.S. Dental Prod., Sweden/USA)or TempCanal (Pulpdent Corp.; Boston Mass.). In thelatter method, the calcium hydroxide paste is depositeddirectly at the apical foramen from a 27-gauge needleand is then “tamped” to place with a premeasured plug-ger. If some escapes, no great damage occurs. Becauseof time constraints in military dentistry, a US Air Forcegroup recommended compacting a plug of dry calciumhydroxide powder at the open apex and immediatelyplacing the final root canal filling.509

In a comparison of techniques for filling entire smallcurved canals with calcium hydroxide, the University ofNorth Carolina group found the Lentulo spiral themost effective, followed by the injection system.Counterclockwise rotation of a No. 25 file was the leasteffective.510 If the calcium hydroxide deposit is thickenough and well condensed, it should serve not only asa stimulant to cemental growth but also as a barrier toextrusion of well-compacted gutta-percha obturation.

Efficacy of Calcium Hydroxide Apical Obturation.The University of Washington group reported goodresults with calcium hydroxide plugs. Both calciumhydroxide and dentin chips worked equally well con-trolling extrusion of filling materials. Although“…both plugs resulted in significant calcification at theforamen…the dentin plugs were complete…” No sig-nificant difference in periradicular inflammation wasnoted.496 However, Holland noted persisting chronicinflammation and a wide variance in hard tissue depo-sition.495 One would suspect contamination by oralbacteria compromised his results.

A University of Alabama group tested for microleak-age canals filled by lateral compaction but blocked atthe apex with three forms of calcium hydroxide: calci-um hydroxide-USP, Calasept, or Vitapex (DiaDentGroup International; Burnaby, B.C., Canada). Therewas no significant difference in leakage among thethree forms of calcium hydroxide.511 Weisenseel et al.confirmed much the same, stating that “…teeth withapical plugs of calcium hydroxide demonstrated signif-icantly less leakage than teeth without apical plugs.” Allwere filled with laterally compacted gutta-percha.512

INJECTION OR “SPIRAL” OBTURATION

By all accounts, filling the entire root canal by injection,or pumping, or spiraling material into place has greatappeal. Unfortunately, the methods fall short, eitherbecause the technique is inappropriate or the materialsused are inadequate.

Already discussed are the deficiencies encounteredwhen warm gutta-percha is injected from one of thesyringes to fill the entire canal. These inadequacies arecaused by shrinkage from the heated to the cooledstate, by failure to compact and eliminate voids, or byextrusion—serious overfilling.

An earlier favorite method of filling the canal withchloropercha and pumping it into place withgutta-percha points failed because of the severe shrink-age from chloroform evaporation.383 This method wasfollowed by totally filling the canal with injected ZOEcement, which will provide an immediate seal, but isoften subject to dissolution and leakage over the years,leading to eventual failure.

Fogel tested five sealers placed in canals with a pres-sure syringe. After 30 days, he found that AH-26, Cavit,Durelon, and ZOE cement all exhibited microleakage,although AH-26 had the least marginal leakage and wasthe easiest to manage.513

The fate of totally obturating canals with cementsalone using a Lentulo spiral was sealed when a numberof disasters of gross overfilling with N2 or RC2B werereported. The material itself could hardly be blamed,even though it is quite toxic. Rather, the blame falls onthe dentist misusing the device in a spinning handpiece(Figure 11-90). The Lentulo spiral will also causeunderfilling if not carefully monitored (Figure 11-91).

One possible exception to the dangers and foibles ofinjecting filling material into the root canal may liewith the emerging hydroxyapatite as an obturant. Inthis case, the calcium phosphate powders are mixedwith glycerine and the paste is injected into the canal.The moisture left in the canal and the apical moisturecause the paste to set to hydroxyapatite. If the materialis extruded, it resorbs and will be replaced by bone.Admittedly, neither the technique nor the product havebeen thoroughly researched to date.137,138,163,164

DOWEL OR POST PREPARATION:POSSIBLE LEAKAGE

Once again, what comes out of the canal may be moreimportant than what goes in. In this case, it is theremoval of a coronal portion of the root canal filling toaccommodate post or dowel placements.

Obturation of the Radicular Space 643

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644 Endodontics

At Louisiana State University, two studies have beencarried out examining the method of gutta-percharemoval, the sealant used for obturation, and the lengthof the interval between obturation and the removal ofgutta-percha to form the “posthole.”514,515

The three removal methods were as follows:

1. Use of a hot plugger2. Use of Peeso reamers3. Use of chloroform and K-files

The results are very interesting: the method ofremoval did not seem to particularly affect the leakageresults, whereas the time of removal was quite signifi-cant. If a hot plugger is used, the best results areachieved if the posthole gutta-percha is removedimmediately after obturation.514 If Peeso reamers orchloroform and K-files are used, however, the removalshould be delayed 1 week to allow for the final set of thecement sealer.515 Conjecture is that the hot pluggerserved immediately as a form of vertical condensation,improving the seal.

Other studies have essentially confirmed these find-ings. A US Army group found no significant difference

Figure 11-90 Gross negligence in canal instrumentation and obturation. A, Apical perforation into maxillary sinus. B, Gross overfilling bysyringe leads to chronic sinusitis. Dentist was found guilty of negligence.

Figure 11-91 Three failures of teeth with paste-filled canals. Rightto Left, Second molar shows periradicular lesion and root resorp-tion as well as osteosclerosis indicating chronic inflammation. Firstmolar has distal root resorption indicative of chronic inflamma-tion. Premolar has broken Lentulo spiral at apex and mesial lateralperiradicular lesion associated with porous root canal filling.(Courtesy of Dr. Worth Gregory.)

A B

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in microleakage when they removed all but 4 mm oflaterally condensed gutta-percha and sealer with fourdifferent methods of removal: a flame-heatedendodontic plugger, an electrically heated Touch ’nHeat spreader, Peeso reamers, and GPX burs.516 GPXburs (Brasseler; Savannah, Ga.) are designed specifical-ly to remove gutta-percha and will not engage thedentin walls (Figure 11-92). Others have evaluated theefficacy of the methods used in filling canals prior topost preparation. In a Belgian leakage study,researchers found “no significant difference betweenobturation techniques”: silver points, lateral com-paction, warm/vertical compaction, Ultrafil injected, orObtura technique.517

At Loma Linda University, lateral and vertical obtu-ration was followed by gutta-percha removal with hotpluggers down to 5 to 6 mm from the apex. Coronalleakage studies in these specimens were then comparedwith Thermafil obturation in which the metal-core car-rier was notched 5 to 6 mm from the tip and then twist-ed off after the obturator was fully into place. “The api-cal plugs in the Thermafil group had the highest degreeof coronal dye penetration.” The reason behind a coro-nal leakage study was based on the fact that cementedposts have an inherently weak seal and that oral fluids(with bacteria) penetrate apically alongside the postand may reach the periapex if the apical gutta-perchaplug fails.518

Saunders et al. found in apical leakage studies thatwhen Thermafil plastic core carriers were used, the sealwas not adversely affected by either immediate ordelayed post preparation.519 Mattison found little dif-ference between Thermafil plastic and metal carri-ers.520 A significant Swedish report of periradicular

radiolucencies found that 15% of the failure cases hadposts in place. The important findings, however, werethe relationships to the length of the remaining apicalplug and the ineffective cemented seal of the post. Asignificantly higher percentage of failures was relatedto apical fillings under 3 mm (Figure 11-93), and 24%of the posts with improper cement seal were associatedwith periradicular radiolucencies.521

REMOVAL OF DEFECTIVE ROOT CANAL FILLINGS AND OBJECTS AND RE-TREATMENT

Endodontists have long complained that their specialtyhas regressed from primary care into “re-treatodontics.”Many specialists note that 30 to 50% of their practice isre-treatment. That includes having to take over a par-tially treated case, or worse yet, having to remove defec-tive root canal fillings and entirely redo the treatment.

Chenail and Teplitsky reviewed the iatral as well aspatient-placed objects that block root canals. Amongthe iatral obstructions, they listed paper points, burs,files, glass beads, amalgam, and gold filings (and, onemight add, plugger and spreader tips, and of coursegutta-percha, cements and sealers, broaches, silverpoints, and posts). Among the objects placed bypatients in teeth left open to drain, they listed nails,pencil lead, toothpicks, tomato seeds, hatpins, needles,pins, and other metal objects.522 Numerous methodsand devices have been developed to retrieve andremove these obstructions.

Gutta-percha and Sealer Removal. Comparedwith other filling materials, gutta-percha and sealer are

Obturation of the Radicular Space 645

Figure 11-92 Brasseler GPX gutta-percha remover fits low-speedhandpiece and features spiraled vents through which gutta-perchaextrudes coronally as it is plasticized by frictional heat. (Courtesy ofBrasseler, USA, Inc.)

Figure 11-93 Frequency of periradicular lesions related to thelength of the remaining gutta-percha root canal filling in 424endodontically treated roots with posts. Note the much lower fail-ure rate with 3 mm or more remaining filling. Reproduced withpermission from Kvist T et al.521

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relatively easy to remove. After the canal orifice of thedefective filling is uncovered, the adhesion of thegutta-percha is tested with a fine Hedstroem file. Thatis, an attempt is made to pass the file alongside the fill-ing to the apical stop. If the filling is really defective, itmay be lifted out by blades of the file, or possibly, withtwo fine files, one on either side of the gutta-percha.

If the gutta-percha is solid but the filling failedbecause it is well short of the apex, a hot plugger maybe repeatedly plunged into the mass, bringing outgutta-percha each time. As much of the filling as possi-ble should be removed by heat before instruments areused to complete the job. Pieces of filling in the canalhave been known to divert the file, and with persist-ence, a perforation may be developed (Figure 11-94).Peeso reamers, Gates-Glidden drills, and round bursshould not be used because they are easily diverted. AGPX gutta-percha remover is less dangerous in alow-speed handpiece because it coronally extrudes thefrictionally heated gutta-percha without contacting thedentin walls (see Figure 11-92).

Occasionally, gutta-percha solvents will need to beused. Again, a “well’’ is made in the center of the defec-

646 Endodontics

tive filling and one or two drops of solvent are intro-duced from a syringe or the beaks of cotton pliers. Thereaming and filing actions are much improved as thegutta-percha dissolves. One must be careful, however,not to pump the liquified mixture out through the api-cal foramen. Larger files are used high in the canal,decreasing markedly in size toward the apex.523

After the bulk of the old filling is removed, aggres-sive filing is done in an attempt to remove all of thegutta-percha and sealer from the walls. Plaques ofsmear layer, debris, and bacteria must be uncovered toensure future success.

The solvents commonly used to liquefy gutta-perchaare chloroform, xylol, eucalyptol, and halothane.Chloroform has been the favorite but fell into disfavorfrom a carcinogenic scare. Halothane was recommend-ed as a substitute even though it is harder to obtain.With the lifting of the FDA ban on chloroform, fear ofit waned and it is still widely used.

A number of studies evaluated solvents plusmechanical means of filling, namely, removal and rein-strumentation. Chloroform was used successfully inbypassing gutta-percha in well-sealed canals using aCanal Finder System with K-files. The vertical stroke ofthe Canal Finder handpiece served well to carry thefiles to the apical stop in an average of 32 seconds in thein vivo cases.524

Wilcox et al. found that no technique or solventremoved all of the debris, although it appears that ini-tially using heated pluggers, followed by chloroformwith ultrasonic instrumentation, had a slight edge.525

Wilcox later found canals were no cleaner when eitherchloroform or sodium hypochlorite was used.526

Others have compared chloroform with other sol-vents, and each time chloroform comes out ahead as themost rapid and complete solvent.527–531 Chloroformdissolves gutta-percha nearly three times faster thanhalothane.528 A US Navy group found “halothane to bean acceptable alternative to chloroform,” particularlywhen used with ultrasonic instrumentation.530 AtCreighton University, a group found both chloroformand halothane effective in removing Thermafilgutta-percha fillings with plastic cone carriers.531

Re-treatment Success Following Gutta-percha andSealer Removal. Bergenholtz et al. examined 660teeth after re-treatment for failures and reported a 94%success rate 2 years later. Of the cohort with periradic-ular radiolucencies, however, 48% completely healed,30% appeared to be healing, and 22% remained as fail-ures.531 They later reported that, when teeth with peri-radicular lesions had overextensions during retreat-ment, success was significantly reduced.532

Figure 11-94 Perforation (arrow) developed during attempt toremove old gutta-percha filling. Small pieces of gutta-percha willdivert endodontic instruments leading to perforation.

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Block and Langeland reported re-treatment of 50endodontic failures that had been filled with N2. Theytoo stated that “…paste placed beyond the foramencaused tissue damage and reduced prognosis.”533

Hard Paste Filling Removal. Gutta-percha andsoft sealer removal is one thing, but removing hardpastes and cements such as N2, zinc phosphates, andsilicates, that have no known solvents, is quite another.Krell and Neo reported the successful yet laboriousremoval of hard pastes using a Cavi-Endo ultrasonicunit.534 At the University of Minnesota, using an Enacultrasonic device with continuous water irrigation anda No. 30 file, they were able to remove hard paste fill-ings in 3 minutes in one case and 10 minutes in anoth-er. The Enac unit vibrates at 30,000 Hz and had to beoperated at the full setting of “8” to be effective. TheCavi-Endo vibrates at 25,000 Hz.535

Silver Point, Post, and Obstruction Removal. Theremoval of a cemented silver point is usually more diffi-cult than the removal of gutta-percha. If the point is bro-ken off down in the canal, a method suggested byFeldman536 in 1914 and modified by Glick (D. Glick, per-sonal communication, February, 1965) may be used. Glickforces three fine Hedstroem files down alongside the pointas far as they will go (Figure 11-95, A). The three files arethen twisted around one another, thus entangling the softsilver point in a grip much like that exerted by a broachholder (Figure 11-95, B). This method has also been com-pared with the grip exerted by the trick Mexican straw“finger-cot” that becomes tighter the harder one pulls. Thegradual pull on the files often loosens the silver point. Thisprocedure may be repeated a number of times, each timeloosening the silver point a bit more.

Getting down alongside the point to get a purchasewith the files may be difficult. Using a No. 1/2 roundbur in a slow handpiece, removing sealer and dentinbut not nicking the point, is a start. After this, smallfiles, chloroform, and/or EDTA may extend the dis-tance alongside the point to allow deeper penetrationwith the very fine Hedstroem files.

If the point has fortunately been left protruding intothe pulp chamber, a sharp spoon excavator or curettealso may be used to pry the point from its seat. A moreefficient spoon excavator has been marketed by Stardentwith a triangular notch cut out in the tip of the blade.With this modification, the blade grips the silver fromtwo sides rather than just by the curve of the blade,(Figure 11-95, C). Silver points may sometimes begrasped with an alligator ear forceps or an ophthalmicsuture holder (Castroviejo curved) (Hu-Friedy;Chicago, Ill.), broken loose from the cement by twisting,and removed.

Rowe has devised another technique using cyano-acrylate glue (Permabond or Superglue #3) and hypo-dermic needles (A. H. R. Rowe, personal communica-tion, 1981). From an assortment of different gauge nee-dles, one is selected that fits snugly, like a sleeve, overthe protruding silver point. The bevel is removed,blunting the needle, which is then cemented over thesilver point. After 5 minutes of setting time, the needleis grasped with pliers or heavy hemostat and the silverpoint “worried” from place (Figure 11-95, D). A varia-tion of this method uses a larger-gauge needle and asmall Hedstroem file. The piece of blunted needle isplaced over the butt of the silver point. The file is theninserted down the inside of the needle and wedgedtightly into the space between (Figure 11-95, E).

Another unique approach uses orthodontic ligaturewire and plastic tubing. First, a groove is cut around theprotruding butt end of the silver point with a halfround or wheel bur. The ligature wire is then doubledover, and the two free ends are passed through the tub-ing to form a loop at the end. The groove in the silverpoint is then “lassoed” with the wire loop (Figure 11-95, F), which is cinched up tight with the plastic sleeve.Adding a drop of cyanoacrylate cement may improvethe grip. The tubing is tightly grasped with pliers or ahemostat and the point is worked loose.537

Acknowledging the source (see Figure 11-95, D),Johnson and Beatty developed a commercial version ofthis tube/cyanoacrylate device. It may be used toremove silver points, broken files, cemented posts, ormetal carriers of Thermafil.538 The EndoExtractor(Brasseler, USA) consists of tubular, trepan-end cuttingburs described by Masseram,539 along with a variety ofsizes of tubes with handles attached. Thedifferent-sized trepan burs fit over the point/post andare used to cut a trench around it, thus freeing a fewmillimeters of the point that may be grasped. Anappropriate-sized hollow-tube extractor is chosen thatwill snugly fit the extruding point.The extractor is thencemented to at least 2 mm of the point with cyano-acrylate glue, and 5 minutes are allowed for it to set.The handle on the tube may then be used to twist andlift the point from its seat. At the University ofMinnesota, researchers have reported the successful useof the EndoExtractor to remove posts, silver points,and broken files when all else failed.540

An improved version of the Endo Extractor(Roydent Dent. Prod., USA) uses the same principle,except that a “Jacobs chuck,” activated by a twist of thehandle, grasps the point/post, so that it may be pulledfrom the canal. Ruddle has also developed a post puller,the Ruddle Instrument Removal System (IRS)

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648 Endodontics

Figure 11-95 Methods of removing silver points. A, Three fine Hedstroem files are worked down alongside silver point. B, By clockwisemotion, three files are twisted around each other, forming vise-like grip on soft silver that can then be dislodged. C, Special “split-tongue”excavator used to pry point from place. D, Blunted hypodermic needle that fits tightly over silver point attached by cyanoacrylate. Whenadhesive sets, needle is grasped with pliers or heavy hemostat. E, Loose-fitting blunted hypodermic needle is placed over silver point.Hedstroem file is wedged alongside and used to “worry” point loose. F, Loop of orthodontic wire in plastic sleeve used to “lasso” groove cutin silver point. Cyanoacrylate may be used to improve attachment.

A B C

D

E F

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(Dentsply/Tulsa Dental; Tulsa, Okla.), that trephinesaround the post by ultrasonics, then screws onto it andlevers the post from the canal.

Ultrasonic/Sonic Removal of Canal Obstructions.“The tightly fitted, well-cemented silver point that isflush with the canal orifice is a challenge to remove.”541

In these cases, and in the case of cemented posts,removal is enhanced through the use of sonic or ultra-sonic devices. At the University of Iowa, researchersplaced a fine Hedstroem file down into the canal along-side the defective silver point. The file was then enervat-ed by a Cavitron scaler and slowly withdrawn (Figure11-96). A number of tries were usually necessary beforethe silver point loosened and could be retrieved.

At UCLA, Kuttler activated posts with a Cavitronscaler until the cement seal was broken and the postcould be either extracted or unscrewed.

Deeper in the canal, the ultrasonic CaviEndoendodontic unit, mounted with a No. 15 file, can beused to loosen obstructions and often “float” themout.523 At the University of Saskatchewan, it wasreported that copious water irrigation was necessaryand that “gentle up and down strokes were used untilthe fragments floated out…” They removed not onlysilver points and broken files, but spreader and bur tipsas well. They warn that patience is needed.522

In Germany, the use of the Canal Finder System ver-tical stroke handpiece retrieved 50% of the defective sil-ver points and fractured instruments. Alternate use of anultrasonic activated file was also recommended.542

One must conclude that the ultrasonic and sonichandpieces have added a whole new dimension toclearing obstructed canals, whether soft gutta-perchaand sealer, hard setting cements, or metallic objectsthat must be removed for re-treatment.

TEMPORARY CORONAL FILLING MATERIALS

An unusual amount of research time and effort hasbeen expended in testing the efficacy of various inter-mediate coronal filling materials. At the outset, it is safeto say that neither gutta-percha nor temporary stop-ping is presently used. Since those days, quickly placed,yet apparently adequate, cements such as Cavit(Premier Dental, King of Prussia, Pa.) have dominatedthe field.

To properly select a temporary, one should know thecriteria for selection.“The role of these cements is to pre-vent the root canal system from becoming contaminatedduring treatment by food debris, buccal fluids andmicroorganisms.”543 Torabinejad et al. have pointed outthat, during or after treatment, root canals can be con-taminated under several circumstances: (1) if the tem-porary seal has broken down, (2) if the filling materialsand/or tooth structure have fractured or been lost, and(3) if the patient delays final restoration too long.544

The properties that a good temporary material mustpossess have been well delineated by Frenchresearchers: good sealing to tooth structure againstmarginal microleakage, lack of porosity, dimensionalvariations to hot and cold close to the tooth itself, goodabrasion and compression resistance, ease of insertionand removal, compatibility with intracanal medica-ments, and good esthetic appearance.543

This same French group has produced the definitivestudy on the leading temporary cements presently on themarket: Cavit and IRM and TERM (Dentsply/Caulk,USA). They note that Cavit is a premixed paste suppliedin collapsible tubes, that IRM is a ZOE cement rein-forced by a polymethylemethacrylate resin, and thatTERM is a light-cure composite (urethane dimethacry-late polymer resin).543

Others have learned that Cavit can cause discomfortin vital teeth, probably through dessication. Also, it is amoisture-initiated, autopolymerizing premixed calci-um sulfate polyvinyl chloride acetate cement, and itexpands while setting.545 IRM must be mixed on a slab,and thus porosity may be incorporated; TERM isinjected into the cavity and light cured for 40 seconds.

French researchers used bacteria in their microleak-age study because bacteria are the principal problem.Streptococcus sanguis, an oral pathogen, is 500 timesgreater in size than blue aniline dye. Therefore, any

Obturation of the Radicular Space 649

Figure 11-96 Removal of silver point flush with canal orificebeing removed with ultrasonic aid. Hedstroem file is placed along-side point and ultrasonic scaler is activated as file is withdrawn.Reproduced with permission from Krell KV et al.541

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leakage indicates “wide” gaps or high porosity. TheFrench group placed temporary fillings 4 mm thick andtested leakage after 4 days of immersion in bacteria,and then after thermocycling from 4 to 57˚C.

They found that Cavit and TERM did not allow bac-teria to penetrate before or after thermocycling, whereas30% of the IRM fillings let S. sanguis pass before thermo-cycling and 60% of the IRMs leaked after thermocycling.They believe that IRM was leaking through the fillingmaterial itself because of mixing porosity, as well as mar-ginally.543 There is no question that, for short-duration,intermediate fillings, Cavit and TERM are preferred.

Seven years later, the French group again tested theefficacy of Cavit, IRM, TERM, and a new adhesive,Fermit (Vivadent, France/USA), via leakage studies.546

They concluded that “Cavit was more leakproof thanthe other cements at day 2…and at day 7.” Cementthickness averaged 4.1 mm.546

In Taiwan, a new temporary material, Caviton (G-CDental, Japan/USA), was tested against Cavit and IRM.The Chinese reported that Caviton provided the bestseal, followed by Cavit. IRM was a poor last.547

Others have tested these materials (Cavit, IRM, andTERM) and other temporary cements as well. Theresults are confusing, probably because of the indicatordyes used, the significant temperature changes,548–550

the stresses of mastication,551 the softening effect ofmedicaments,552,553 and the length of time the fillingswithstand the variables.554

Some found that Cavit must be at least 3.5 mmthick,554 and that one should not plan an “intervisitperiod for longer than 1 week.553,555 Most found Cavit,Cavit-G, and Cavit-W (hardness variations) as good as,if not the best of, the temporaries.543,555–563, 567 Othersfound Cavit less adequate than IRM and ZOEcements.550,551,564,568–570

Many studies agreed with the Deveaux group in Lille,France, that TERM was superior or equal to all of theother temporary coronal sealants.543,558,561–564,571 Atthe Universities of Iowa, Saskatchewan, and California,workers disagreed with the value of TERM as asealant.556,559,560 Most others also agreed with Deveauxthat the use of IRM is ill-advised, and that it leaks badlybefore and after thermocycling.543,558,559,562–564

More recently, a Berlin group found it efficacious toadd glass-ionomer cement to temporary replace-ments.572 They reported “that only glass-ionomercement and IRM combined with glass-ionomer cementmay prevent bacterial penetration to the periapex ofroot filled teeth over a 1 month period.”572

Some research groups found zinc phosphate andpolycarboxylate cements most inadequate,562,563 but

650 Endodontics

the glass ionomer Ketac Fil to be quite adequate if thecavity is first acid etched. This rather time-consumingapproach gave a similar result to Kalzinol (Dentsply/DeTrey, Switzerland/USA), a reinforced ZOE cement.555

There are other factors that might affect the tempo-rary seal, one being the intracanal medicaments thatcould dissolve and loosen the seal from below. Rutledgeand Montgomery found, however, that neithereugenol, formocresol, nor CMCP broke the seal ofTERM, although the “walking bleach” paste of sodiumperborate and superoxol did so.573 Another group sug-gested that a pellet of cotton soaked in a medicament(CMCP) would act as a barrier if bacteria leakedthrough the temporary filling.574

Does a filling already in place that is penetrated by theaccess cavity have any effect on microleakage? The answeris yes on two counts. First, the filling itself may be faultyand leaking, and second, the temporary filling-in-the-fill-ing may not adhere, and leakage will ensue.

If one suspects that the filling to be perforated foraccess is already faulty, it should be totally removed.560

If this happens, a temporary filling will have to with-stand the trauma and abuse suffered by a two- or three-surface filling. In this event, a temporary material mustbe chosen to withstand these stresses. At the Universityof Georgia, researchers determined that “TERMrestorations provided excellent seals and were statisti-cally superior to Cavit and IRM for restoring complexendodontic access preparations.” IRM leaked immedi-ately from “thermal stress.” Cavit has a setting expan-sion of 14%, so that it literally “grew” right out of ClassII cavities and severely cracked. Its low compressivestrength and high solubility made it unacceptable forlong-term use.564

At the University of Georgia, workers preparedendodontic access cavities in Class I amalgam fillingsand then restored the access cavities with various tem-porary materials. Glass ionomer, TERM, Cavit-G, andIRM “all provided excellent seals” for up to 2 weeks,whereas zinc phosphate and polycarboxylate cementsproved inadequate. No thermocycling was done. Ittends to break the seal of all of these materials placed inamalgam cavities.565

At Indiana University, they tested ZOE and Cavit incavities prepared in amalgam and composite. They foundthat “ZOE seals against marginal leakage better than Cavitwhen the access opening is placed through compositeresin, and that Cavit seals better than ZOE when the accessopening is placed through amalgam.” Thermocyclingapparently broke the bond with amalgam.566

Torabinejad et al. pointed out the importance of thetemporary seal lasting even after root canal therapy is

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completed, emphasizing the importance of early finalrestoration of the tooth. It took only 19 days forStaphylococcus placed in the crown to reach the apex in50% of the test cases and 42 days for 50% of the Proteussamples to do the same.544 The Torabinejad team laterreported that bacteria in natural saliva will contami-nate root canals obturated by either lateral or verticalcompaction, from crown to apex, in just 30 days if leftopen to the saliva.575

At Temple University, it was found that bacterialendotoxin could penetrate the full length of an obturat-ed canal in just 20 days.576 More recently, the Iowa groupfound that endotoxin, “ a potent inflammatory agent,may be able to penetrate obturating materials faster thanbacteria.”577 They also extended the caveat: “the need foran immediate and proper coronal restoration after rootcanal treatment is therefore reinforced.”577

One must conclude from this full discussion thattemporary fillings are most important in multiple-appointment treatment to prevent recontaminationbetween appointments and, further, that the materialmust be tough enough to withstand mastication.Between-appointment intervals should not exceed 1week, and the temporaries must be thick enough toprevent leakage. Finally, long-term temporization isinadvisable.

TERM and glass-ionomer cement appear to be themost acceptable temporaries, followed by Cavit in ClassI cavities. ZOE, zinc phosphate, polycarboxylatecements, and IRM, per se, are much less acceptable, and,of course, temporary stopping is totally unacceptable.

FINAL CORONAL RESTORATION:MICROLEAKAGE

It might be that as many root canal fillings fail becauseof bacterial entry from leaking coronal restorations asfail from periradicular leakage. As stated earlier,Torabinejad et al. demonstrated an inordinate (50%)bacterial contamination from the crown clear throughto the apex, around and through well-compactedgutta-percha fillings.544

After bacteria pass permanent occlusal fillings, thereappears to be a clear track right past the bases placedover the root canal filling—either zinc phosphatecement or temporary stopping.578

Melton et al. recommended that leaking permanentrestorations “should be removed in their entiretybefore endodontic treatment”560; it makes even moresense to remove any suspicious restorations after treat-ment as well, not try simply to restore the access cavity.

There is a terrifying body of literature, for example,that testifies to microleakage all the way to the pulp

under full crowns.579–583 One must assume that, alongthese pathways, bacteria could reach the pulp spaceoccupied by root canal fillings and then down the rootcanal filling to the apex.544 “None of the current lutingagents routinely prevent marginal leakage of castrestorations.”582 Furthermore, “…all crowns leakedgingivally regardless of the type of crown marginpreparation.”583

Therefore, it goes without saying that so-called “per-manent” restorations of endodontic access cavities suf-fer microleakage as well. At the University of Iowa,Wilcox and Diaz-Arnold restored lingual access cavitieswith either Ketac-Fil glass ionomer cement orHerculite composite resin (Sybron Endo/Kerr DentalOrange, Calif.). Acid etch was used as well as GLUMAdentin-bonding agent. After thermocycling, all of thespecimens leaked and they leaked right past the zincphosphate and/or temporary-stopping bases under-neath. One specimen even leaked all the way to the api-cal foramen.578

A series of experiments at the University of Iowafound that coronal microleakage, in the presence ofsaliva, was inevitable up to 85% of the time.584 AtIndiana University, researchers also noted the penetrat-ing effect of saliva and recommended “re-treatment ofobturated root canals that have been exposed to theoral cavity for at least 3 months.”585

To confirm in vivo the penetrating effects of salivafrom leaking coronal restorations seen in vitro,586 theIowa group did coronal microleakage studies on mon-keys. They reported dye penetration down the filledroot canals no matter which sealer was used: Sealapex,AH-26, or ZOE.587

Undoubtedly, one of the causes of microleakageunder cemented restorations relates to the dissolutionof the cement. Phillips et al., in a human in vivo study,found that zinc phosphate cement was much morelikely to disintegrate than were polycarboxylate or glassionomer cements.588 This is particularly importantbecause zinc phosphate is still the most widely used lut-ing agent.

If all of these standard luting cements are faulty intheir sealing ability, what is one to do to preventmicroleakage? The answer appears to lie in the use ofthe new adhesive resins, or glue that will adhere to alltooth structures, as well as metals, other resins, andporcelain.

Tjan, Tan, and Li, at Loma Linda University, haveshown that when the 4-META adhesive Amalgambond(Parkell Dental, Farmingdale, N.Y.) is used to line boththe prepared dentin and enamel, the newly placedamalgam filling is virtually leakproof (Figure 11-97, A).

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In contrast, a cavity lined with Copalite allowed leakagearound the amalgam as far as the pulp589,590 (Figure11-97, B). Amalgambond can also be used to bond newamalgam to old amalgam, or composite to amalgam,gold, or other composite. Another 4-META product,C & B Metabond (Parkell Dental, USA), will lute gold orporcelain restorations to tooth without future leakage.

Wilcox attempted to use GLUMA (MilesLaboratories, USA), the dentin-bonding agent, toadhere a composite resin to the tooth structure ofendodontic access cavities in anterior teeth. After ther-mocycling, it failed.578

At this juncture, the solution to the problem ofmicroleakage appears to be the resin-adhesive agents,particularly those that will adhere to more than justother resins, and possibly another approach—placingan intraorifice barrier base, medicated or nonmedicat-ed, over the coronal root canal filling.

At the University of Tennessee, the Himel groupplaced pigmented glass-ionomer cements over thecoronal termination of the root canal filling. Theyreported that “the teeth without an intraorifice barrierleaked significantly more than the teeth with the [glass-ionomer] barriers (p < .05).”591 Similar research at

652 Endodontics

Northwestern University revealed much the sameresults—the root canals that received an intraorificebarrier leaked significantly less than the unsealed con-trols, all of which leaked in < 49 days.592

At the University of Toronto a different approachwas tried—sealing the canals with two experimentalglass-ionomer sealers, one containing an antimicrobialsubstance. The first sealer proved effective in prevent-ing the “penetration of E. faecalis” probably because ofthe natural release of fluoride. The experimental sealerwith the added antibacterial “needs more study.”593

Martin has recently introduced gutta-perch pointsand an accompanying ZOE sealer, both of which con-tain iodoform, a well-known bacterial suppressant. Invitro results appear promising; however, long-term invivo efficacy has yet to be shown. The products aremarketed as MPG gutta-percha points and MCS rootcanal sealer (Medidenta Products, Woodside, N.Y.).

A NEW ENDODONTIC PARADIGM

It has been recognized for decades that the ideal endresult of root canal therapy would be the closure of theapical and all lateral foramina with reparative cemen-tum.594,595 This permits re-establishment of a complete

Figure 11-97 Comparative study in microleakage between resin adhesive and copal varnish. A, Amalgam filling bonded to dentin (D) andcementum (arrow) with Amalgambond and no microleakage. B, Amalgam filling lined with Copalite. Gross microleakage at gingival floor(arrows) as well as from upper margin (curved arrow). (Courtesy of Drs. A. H. L. Tjan and D. E. Tan.)

A B

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attachment apparatus and precludes future failurecaused by pulpoperidontal fluid exchange and retroin-vasion of bacteria.

Following well-executed treatment, wherein infec-tion and irritation are terminated, cementoblasts andperiodontal ligament slowly resurface the damagedroot and even close minor foramina that no longercontain neurovascular bundles.

But well-obturated major foramina that present a sur-face of sealers and/or gutta-percha to the periradiculartissue will not be closed over. Cementum will not growacross mildly irritating sealer surfaces. This leaves theseforamina vulnerable to leakage as cement sealers dissolveaway over the years. How can this dilemma be resolved?

Cementification. In the last two editions of thistext, Ingle and Luebke made a case for the wider use ofcalcium hydroxide as a stimulating and healing agent(Figure 11-98). The same thought occurred to others—to use calcium hydroxide in filling the canal as well asan interappointment canal medicament.595–597

Today, these speculations have become a reality.Calcium hydroxide is frequently being used as an apicalplug before total obturation.499–526,598 Furthermore,calcium hydroxide is being incorporated into rootcanal sealers in such commercial products as CRCS andSealapex. Although the reviews have been mixed onthese latter products, there have been some favorablereports, but not without unfavorable side effects fromoverfilling.105–111,153–160,599–601

A Turkish group found “hard tissue formation morepronounced after root filling with Sealapex than withcalcium hydroxide…”600 However, a Tel Aviv group

reported that the “…disintegration of Sealapex indicat-ed that solubility may be the price for increased activi-ty.”601 In other words, these sealers must dissolve torelease their calcium hydroxide. It then becomes aquestion of which will happen first—cementificationacross the apex or leakage into the exposed canal withits attendant problems? Is there a substitute for calciumhydroxide that may have its stimulating effects but notits drawbacks? The answer may be hydroxyapatite!

Calcium-Phosphate Cement Obturation. Yearsago, Nevins and his associates were using cross-linkedcollagen–calcium phosphate gels to induce hard tissueformation.602 More recently, Harbert has suggestedusing tricalcium phosphate as an apical plug, much likedentin shavings and calcium hydroxide have beenused.603 Even more recently, calcium phosphate cement(CPC) has been suggested as a total root canal fillingmaterial.138

The ADA-Paffenbarger Dental Research Center atthe US National Institute of Standards and Technologyhas developed a simple mixture of calcium phosphatesthat sets to become hydroxyapatite.“Two calciumphosphate compounds, one acidic and one basic, areunique in that when mixed with water they set into ahardened mass”—hydroxyapatite—the principal min-eral in teeth and bones.137 Tetracalcium phosphate isthe basic constituent, and the acidic component iseither dicalcium phosphate dihydrate or anhydrousdicalcium phosphate. “Water is neither a reactant noran important product in the reaction, but merely avehicle for dissolution of the reactants.”137 Setting timemay be extended by adding glycerin to the mixture.Using a mild phosphoric acid solution speeds the dis-solution of the components. Even aliquots of bloodfrom a surgical site may be substituted for water.

The final set, calcium phosphate cement (CPC),consists of nearly all crystalline material, and porosityis in direct ratio to the amount of solvent (water) used.It is as radiopaque as bone. It is nearly insoluble inwater and is insoluble in saliva and blood, but is readi-ly soluble in strong acids, which may be considered inthe event it must be removed.137

In testing the sealing ability of CPC when used as aroot canal sealer-filler, the Paffenbarger group report-ed that in most of the specimens there was “no dyepenetration into the filler-canal wall interface”(Figure 11-99). The mean depth of penetration wasonly 0.15 mm overall.

Glycerin was used in mixing the CPC to improve itsextrudability from a 19-gauge needle. A funnel-shapedneedle is being considered (L. C. Chow, personal com-munication, August 1992). As far as tissue response to

Obturation of the Radicular Space 653

Figure 11-98 Calcification forming around nidus of calciumhydroxide in tissue (arrow). (Courtesy of Dr. Raymond G. Luebke.)

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CPC is concerned, the “calcium phosphate treated ani-mals showed mild irritation after 1 month, but thereafterthe adverse tissue reactions were minimal. New bone for-mation adjacent to the cement was also observed.”137 Inanother study, 63% of the specimens “showed no evi-dence of inflammatory response to the CPC.”604 Stillanother study, done on monkeys, in which canals weredeliberately overfilled, new bone formation developed

654 Endodontics

immediately adjacent to the cement218 (Figures 11-100,11-101). Exhaustive tests of CPC by Chinese researchersin Shanghai found that “CPC had no toxicity and all testsfor mutagenicity and potential carcinogenicity of CPCextracts are negative.” They also noted that “the implanttightly joined with the surrounding bone.…”605

Krell and Wefel also found that, as a sealer, CPCadheres well to the canal wall.606 In marked contrast to

Figure 11-99 Noticeable difference in density of interface between filling materials and dentin wall (D). A, Canal filled with gutta-percha(GP) and Grossman’s cement (GC). Note discrepancies in sealer interface. B, Canal filled with calcium phosphate cement (CPC-A). Denseinterface explains superiority in apical leakage pattern. Reproduced with permission from Sugawara A, et al. JOE 1990;16:162.

Figure 11-100 Periradicular area 3 months after purposeful overfill of canal with calcium phosphate cement CPC. The CPC (C) is borderedby slender new bone trabeculae (NB) at the periphery where foam histocytes (H) are frequently present (right). LB, lamellar bone. A, ×75original magnification. B, ×300 original magnification. Reproduced with permission from Hong YC et al.218

A B

A B

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CPC, leakage was observed in the gutta-percha/ZOEcontrols138 (see Figure 11-99). And at the US NavalDental School, CPC was used as an apical barrier tofacilitate obturation much as dentin chips and calciumhydroxide have been used. “The teeth receiving apicalCPC barriers...had significantly less dye penetrationthan teeth without apical barriers.” They recommend-ed CPC as a replacement for calcium hydroxide inapexification cases.607

Japanese researchers have already marketed apatitesealers. Two of them, G-5 and G-6, were tested atIndiana University against Super-EBA for biocompata-bility.608 While finding Super-EBA and G-5 biocompat-able, the researchers found G-6 “promoted moderateinflammation and foreign body giant cell response.” Inaddition to CPC, both G-5 and G-6 contain radiopaci-fiers, potassium fluoride, and citric acid, except G-6contained more of the latter.608

A Japanese group at Osaka tested another commer-cial apatite sealer, ARS (Apatite Root Sealer), and foundthat it “caused severe inflammatory reactions.”609 In thesame test, the Osaka group added 2.5% chondroitinsulfate to CP cement (TMD-5) and reported that it“has excellent histocompatability and potential as aroot canal sealer.”609

An Italian company has added hydroxyapatite toZOE sealer, Bioseal (Ogna Lab. Farma., Italy), much ascalcium hydroxide has been added to CRCS sealer.Whereas Gambarini and Tagger reported that Bioseal“did not adversely affect the sealing properties” of thecement, its beneficial effects were “not within the scopeof the study.”610

In an entirely different direction in the developmentof apical barrier materials, Japanese researchers havetested the use of freeze-dried allogenic dentin powder

as well as True Bone Ceramics (TBC), the latter derivedfrom the incineration of bovine bone.611 Initially, withboth products, multinucleate giant cells and boneresorption appeared. Within 3 months, however, newbone had formed and “the apex had been closed com-pletely with new hard tissue.”611

If a delivery system can be perfected for CPC, itcould well be the sealer/barrier/filler of futureendodontics. The Paffenbarger Center did find thattheir material provided better sealant qualities than didZOE and gutta-percha.165 The fact that hydroxyapatiteis a naturally occurring product, and that bone growsinto and eventually replaces extruded material, makesit very acceptable biologically.612 Moreover, it mayreplace calcium hydroxide in treating open-apex casesand fractured roots.

Another possibility of using hydroxyapatite relatesto the laser. A cross-linked collagen-hydroxyapatitemixture has been placed in the root canal and “melted”to place with a laser beam through a fiber optic.

To date, none of these uses of calcium phosphatecements have been approved by the US Food and DrugAdministration, although clinical trials have beenapplied for. This long, slow, and costly process must beundertaken before the products can be released for useby the profession. More recently, an experimentalmaterial, mineral trioxide aggregate (MTA), has beensuggested as a root-end filling material.613 This mayalso turn out to be a promising material for use as anorthograde filling of the apical end of the root canalprior to filling the remainder of the canal withgutta-percha. It is presently being used primarily as aretrofilling material.

Adhesive Resins. Very little has been published onthe use of adhesives in filling root canals.126,130,131 It

Obturation of the Radicular Space 655

Figure 11-101 Periradicular area 6 months after CPC overfill. A, Numerous ossification nidi (arrowheads) extend in various directions tocommunicate with one another. Surrounding calcium phosphate cement (C), better seen in B, high power (×300 original magnification). LB,lamellar bone. Reproduced with permission from Hong YC et al.218

A B

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stands to reason that adhesive resins could serve to sealdentin walls after smear removal. If it can be made toadhere to other filling materials such as gutta-percha,and if it can be made radiopaque without ruining itssetting and adhesive qualities, one would think thatadhesives may have a bright future in endodontics.Amalgambond already has been used to seal amalgamretrofillings against microleakage.

At the University of Minnesota, Zidan and El Deebfound that Scotchbond, which bonds chemically to cal-cium, provided a significantly better seal thanTubliseal.130,131 In Australia, Gee found that he couldonly achieve a result comparable to lateral compactionwith AH-26 as a sealer by falling back on a complex sys-tem involving GLUMA as a bonding agent, followed byConcise composite, plus AH-26 and gutta-percha.GLUMA and Concise alone gave a poor leakage result.614

This hardly speaks well for GLUMA or Concise.Kanca has shown that certain “bonding” agents will

not adhere to moist dentin. GLUMA is one of these, aswell as Scotchbond II, Clearfil, Photobond, and Tenure.Since it is almost impossible to totally dry a root canal,an adhesive must be selected that bonds to both wetand dry dentin. Kanca recommended All Bond 2 (BiscoDental, USA),615 although Amalgambond and C & BMetabond are just as effective.

SUMMARY

All in all, one must be aware that on the horizon, thereare a number of possible methods of obturating rootcanals that will be “kinder and gentler.” More laborato-ry and clinical research is needed, along with FDAapproval, before a new endodontic paradigm is ful-filled. Endodontics is moving from nineteenth-centurygutta-percha and calcium hydroxide into the twenty-first century of chemistry and lasers. The transition isslow, but exciting.

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