Use of Wide-Diameterand Standard-Diameter

Implants to ReplaceSingle Molars:

Two Case Presentations

Mari<us B. Blatz, DMD'förg R. Strub, DMD, PhD''Rainer Gläser, MDT^Walter Gebhardt, MDT''

Purpose: The ultimate goal in modern esthetic dentistry is the restoration of lost hard and soft(issues by imitating nature as ciosely as possible. With the increasing esthetic awareness ofpatients, surgical and technical developments, and dentists' enhanced skills and knowledge,optimal function and esthetics are achievable even with implant-supported restorations in molarregions. Anatomic and morphologic factors and poor bone quantity and quality might reducesuccess rates of dental implants in the posterior jaw. Today, there are two options to replace asingle missing molar by an implant-supported crown; the single wide-diameter Implant or twostandard-diameter implants. These two approaches are described and their advantages anddisadvantages discussed in two exemplary clinical cases. Materials and Methods: In one case, theedentulous ridge in the area of the mandibular righl first molar (FDI tooth 46) provided sufficientmesiodistal space to restore tooth 46 with a porcelain-tused-to-metal crown on two standard-diameter implants, placed in a root-analog manner. In the other case, the manibular first molarsIFDI teeth 36 and 46) were replaced by porcelain-fused-to-metal crowns on wide-diameterimplants. Results: It can be concluded that both options to replace a single molar provide moresurface area and better biomechanicai properties than one standard implant. Conclusion: Long-term data are needed before these treatment modalities can be recommended for the privatepractitioner, Ittt I Prosthodont 1998:11:356-363.

The highest goal in modern esthetic dentistry isto imitate nature as closely as possible. With

today's surgical and technical possibilities, this canbe achieved to a very high levelJ"^ This is alsovalid for prosthetic restorations supported by im-

Historically, the totally edentulous jaw was themain indication for dental implants, with prosthe-ses supported by implants placed in the anteriormandible and maxilla,''^ ^'' Today, not only aredental implants used successfully in the partiallyedentulous jaw,^^"^"" but implant-supported single-

^Asíiítam Professor, Department of Prosthodontics, Universityof Freiburg, Freiburg, Germany.

''Dean, Professor and Chairman, Department cf Prosthodontics,University of Freiburg, Freiburg, Germany.

•^Master Dentai Technician, Department of Prosthodontia,University of Freiburg, Freiburg, Germany.

''Master Dental Technician, Zürich, Switzerland,

Reprint requests: Dr Markus B. Biatz, Department ofProsthodontics, School of Dentistry, University of Freiburg,Hugstetterstrasse 55, D-79106 Freiburg, Germany.

tooth restorations are becoming more and morecommon,^^"^^

Most clinical studies with single-tooth implantsrefer to implants inserted in the anterior ¡aw, proba-bly because of higher failure rates of dental implantsin premolar and molar sites.-^'^" Certain anatomicand morphologic factors in posterior areas may limitlong-term success rates of implants and differenttreatment modalities are mandatory for those areas.Major limiting anatomic structures are the maxillarysinus in the maxilla and the alveolar nerve in themandible. High occlusal load in posterior regionswhere bone quality and quantity are generallypoorer^' must be considered,^-"^'' Problems withthe use of a standard-diameter implant to restoremolars have been described. Different authors havereported loosening of the gold screws and screw orimplant fracture,^^-^? Those facts, combined withthe discrepancy of a natural molar's diameter com-pared to that of a standard implant, demand the cre-ation of a larger implant surface. Langer et aP^ a^dLazzara^^ suggested using wide-diameter implants.Sufficient bone quantity in the buccolingual dimen-

loumal of Prostliodontif 356 Volume]!,Number4,1998

Fig 1 (Left) Occlusai view otmandible at the beginning ottreatment- edentuious ridge inthe area of tootti 46 and inade-quate restorations in teetti 35and 47.

Fig 2 (Righi) Atter a diagnosticwax-up ot tooth 46, a radi-ograptiic tempiate witti standard-ized metai pins at the optimal im-plant position was manutactured.

Wnie-OiJtncter and Standard-Dianieler implanis to Replace MoiarE

sion is mandatory and limits their application.^^"^^Therefore, the insertion of two standard-diameterimplants for the restoration of a molar was pro-posed.^^"•'̂ •^^ Using two standard-diameter implantsguarantees both a large surface area and a favorableciistribution of occlusai forces. But the mesiodistalspace must be at least 12..̂ mm. This distance is thesum of the two implants' diameters, the minimal in-terimplant space of 1.5 mm, and the minimal dis-tance between the implants and the adjacent toothroots, which should also be at least 1.5 mm.^^'-'^'''''Technical problems at the time of implant place-ment, impression taking, and fabrication of the finalcrown because of limited access have to be takeninto consideration at the treatment-planning stage.Another important issue is the retention of the finalcrown either via cementation or by using a trans-occlusal or lingual retention screw. Cementation ofan implant-supported crown offers optimal estheticsbut limited retrievability. Sometimes the only way toretrieve a cemented crown is to cut it down andthereby destroy it. Both options, esthetics and re-trievability, are achievable when using a lingual re-tention screw. The major disadvantages are screwloosening, thread damage, and cost.

Using two implants to support a single crown in-creases the cost still further and this should be dis-cussed with the patient.

In this article, two clinical cases are presented,showing implant-supported restorations of molarsby two standard-diameter implants and a wide-di-ameter implant. The advantages and disadvantagesof both concepts are discussed.

Case 1

A 25-year-o ld man was referred to tbeDepartment of Prosthetic Dentistry, Albert-1 udwigs University, for placement of an implant-supported crown to replace the mandibular rightfirst molar (FDI tooth 46), which was missing (Fig

1). The treatment planning further included therestoration of the second molar (FDI tooth 47)with a partial coverage crown, and replacementof the amalgam filling in the mandibular left sec-ond premolar (FDI tooth 35) with a compositerestoration. An impression of the mandible wastaken, a diagnostic wax-up of the missing molarwas made, and a radiographie template was man-ufactured. The mesiodistal space between theright second premolar and second molar (FDIteeth 45 and 47) was 13 mm, providing sufficientspace for two implants. Two .3-mm-long metalpins were polymerized into the template in thearea of tooth 46 in positions resembling the posi-tions of the two standard implants that wereplanned to be placed (Fig 2). A panoramic radi-ograph was taken with the x-ray guide in place toevaluate the bone height (Fig 3). The x-ray guidewas converted to a drilling guide by cutting it inhalf and removing the metal pins so that the de-sired implant position could be marked intraoper-atively (Fig 4). After local anesthesia, a crestal in-cision, and elevation of two full-thickness flaps,two titanium plasma-spray (TPS)-coated implants(Steri-Oss) with dimensions of 3.8 x 10 mm and3.8 X 12 mm were placed in a root-analog man-ner. Parallel pins were used for control of implantposition and angulation (Fig ."i). The flaps wereclosely adapted to provide primary wound closurewith interrupted sutures.

After a healing period of 4 months, second-stagesurgery was performed and oval-shaped healingabutments were placed. Four weeks later the heal-ing abutments were removed and transfer pinswere mounted. An impression of the implants andthe prepared tooth 47 was taken using polyetherimpression material (Impregum, ESPF) and a cus-tom-made tray of ultraviolet (UV)-curing resin(Convertray, Wilde). At the same appointment, analginate (Palgaflex, FSPEI impression of the oppos-ing jaw was taken. Using the face bow and check

Volumen,Number 4, 1998 357 The Intern.itionai lournal of Prosllioilontii

éter and Standard-Oiameter ImplanK to Replace Mola

Fig 3 Panoramic raöiograpli wittt >!-ray guide in place to evaluate ttie underlying bone height.

Fig 4 (Leñ) Radiographic tem-plate converted to a drillingguide.

Fig 5 ¡Rigfit) Jvjo Steri-Oss im-plants were used to replace tooth46. Parallel pins show root-ana-og implant position and angula-tion.

Fig 6 (Left) Bio-Esthetic abut-ments were selected and individ-ually prepared in the laboratory.

Fig 7 (Rigfit) Lingual view ofmetal Irame including a lingualretention screw. The metal mar-gin guarantees a precise fit.

bites, the master models were mounted in an ar-ticulator ISAM 2, SAM-Präzisionstechnik], TwoBio-Esthetic abutments (Steri-Oss) of the dimen-sions 7 X 4.7 X 3 mm were selected, mounted onthe implant analogs, and individually prepared inthe laboratory by the dental technician"*^"^^ ¡Fig 6),A metal frame was cast in high precious metalalloy using an index (Formasil i l, Heraeus Kulzer)taken from the diagnostic wax-up. The castablethread for the lingual retention screw {Suprafix,Métaux Précieux Métalor) was included (Fig 7).

The lingual screw allowed the removal of the finalporcelain-fused-to-metal (PFM) crown withoutcompromising the esthetic result. The ceramic ma-terial (Creation, Girrbach-Dental) was fired on themetal framework. After the PFM crown was fin-ished, an acryiic index was fabricated to transferthe post position from the master model to themouth. The Bio-Fsthetic abutments and the PFMcrown, as well as the partial coverage crown fortooth 47, were inserted and a final radiograph wastaken (Figs 8 to 13),

Tfie International Journal of Prosthodontics 358 l,Number 4,1998

Wide-D,amelcr,ir,<ISMndard.Dir n[)l5nt5 in Repbce Mola

Fig 8 Occlusal viewot the acrylic index inposition for abutmentconnection. Try-In otthe partial coveragecrown on looth 47.

Fig 9 Occlusal view ot mandible atter aöLitment connection.

Rg 10 Lingual view ol the final PFM crown on the mastercast.

Fig I I Lingual view of the tinal PFM crown cn two implantsin the area ot tooth 46.

Fig 12 Occlusal view of mandible at the end of treatment:restoration of tooth 46 with metal ceramic crown on two im-plants, partial coverage orown on tooth 47, and composite tiil-ing on tooth 35.

Fig 13 Final raciiograüi^ alltr placomcnt otcrown on two standard-diameter implanta placed in aroot-analog manner and atter cementation ot the partialcoverage crown.

• t 1 , fviimber4, H 359

Wide-Diameter and SWndsrd-Diameter Implant! lo Replace Molars BUl?. et

Fig 14 Occiusai view of mandible at thebeginning of treatment; inadequate com-posite fiilings Oh teeth 35, 38, and 48.

Fig 15 Panoramic radiograph at the beginning of treatment; severe iocaiized boneioss is visibie.

Fig 17 Oociusal view of mandible;heaiing caps are placed on impiants inthe first moiar region; the composite fill-ings on teeth 38, 35, and 48 have beenre piaced.

Fig 16 Panoramic radiograph after several teeth were extracted, some of the teeth inthe maxiiia are restored with provisionai restorations, and three Osseotite implantshave been placed (area of teeth 24, 36, and 46).

Case 2

A 50-year-olcl woman was referred to the Depart-ment of Prosthetic Dentistry, Mbert-LudwigsUniversity, for treatment of her periodontal prob-lems. The treatment planning for the mandiblewas as follows: Extraction of the mandibular firstmolars (FDI teeth 36 and 46) (pocket depths 6 to12 mm, furcation involvement degree 3), scalingand root planing of all remaining teeth, compos-ite fillings of the mandibular right second premo-lar and third molar and left third rrtolar (FDI teeth35, 38, and 48), placement of wide-diameter im-plants in the area of the first molars, and restora-tion with PFM crowns (Figs 14 and 15), The treat-

ment was executed according to the proceduresdescribed in Case 1, In this case, two Osseotiteimplants (3i, Wieland) with dimensions of 6,0 X13 mm were placed (Fig 16), Figure 1 7 shows thesituation 6 weeks after abutment connection andreplacement of the composite fillings {teeth 35,38, and 48), For the fabrication of the PFMcrowns, the prefabricated UCLA (3i, Wieland)burn-ojt patterns with a high precious marginwere used (Figs 18 and 19). Figures 20 to 22show the try-in of the two PFM crowns in themandibuiar first molar regions and the control ra-diograph. For esthetic reasons, the occiusai screwholes were covered with two temporarily ce-mented acrylic inlays {Fig 23),

The international Journal of Proslhodonlii 3 6 0 Volume 11, Number 4, t99B

lí ^' ¡il Wide-Diameter ¡ind Standiird-Dianieter Imiibnts to Reillace Mo/.lr

Figs 18 and 19 Lateral view ot the PFM crowns on the master cast. Notice the metal margin to guarantee a good fit.

Fig 20 Occiusal view of mandible: try-in of the two PFMcrowns on the implants in the area ot teeth 36 and 46.

Fig 21 Radiograph after placement cf the two PFM crownson wide-diameter implants.

Fiq 22 Radiograph atter plaoement of the two PFfWI crownson wide-diameter implants.

Fig 23 Occlusal view ot mandible at llie end of treatment.O«;lusal screw holes are covered witti temporarily cementedacrylic inlays.

Volume 11, Number 4, 199ö 35-J The International lournal ol Prostliodontics

Wide-Diameter and Standard-Diameter ImpianLs lo Repla

Discussion

Anatomic and morphologic factors and poor bonequantity and quality may reduce success rates of den-tal implants in the posterior jaw. If adjacent teeth arecaries-free, have adequate intracoronal restorationsor partial- or full-coverage crowns, a missing molarcan be replaced by an implant-supported crown.Today, there are two options for replacement of amolar: a single wide-diameter implant or two stan-dard-diameter implants. Fven though the advantagesof these treatment procedures are obvious, long-termprognosis of such restorations is unknown.Publications that address this subject are either casepresentations or contain only short-term data. Craveset aH- followed 266 wide-diameter Brânemark im-plants in 196 patients for 2 years. In the mandible,the success rate was 94%, and in the maxilla the suc-cess rate was 98%. Becker and Becker '̂ reported acumulative success rate of 95% for 24 wide-diameterBrânemark implants replacing a single molar over thesame observation period. Bahat and Handelsman^''compared the use of wide-diameter Brânemark im-plants with double implants in the posterior jaw. Thefailure rate was 2.3% for wide-diameter implants(mean loading period: 13 months), and 1.6% for dou-ble implants (mean loading period: 37 months).Balshi et aP^ published a comparative study of singleversus double implants replacing a single molar. The3-year cumulative success rate for both was 99%,whereas the marginal bone loss during the follow-upperiod was significantly higher for the group with twoimplants than for the group with only one implant.

Problems reported when using wide-diameter im-plants to replace a molar were mainly gold screw-loosening and breakage. Insufficient space in amesiodistal direction is the major contraindicationfor the use of two implants in the area of a missingmolar. Even if adequate space is provided, problemsmay occur during implant placement because of un-favorable root angulation of the adjacent teeth. Mostofthe impression transfer posts are not designed foruse in areas with limited space. This might cause se-rious problems with the conventional open-tray orclosed-tray impression techniques, which are evenworse when implants are placed in root-analog con-vergence. With this configuration, impression postsoften have to be customized. The restricted spacebetween two implants placed closely together de-mands advanced manual skills by the patient forproper cleaning and maintenance after placement ofthe final crown. Long-term data are needed beforewide-diameter implants or two standard implantscan be recommended for replacement of a molar inprivate practice.

Conclusion

Wide-diameter implants and double implants to re-place molars provide more surface area and betterbiomechanical properties than one standard im-plant. Long-term data are needed before thesetreatment modalities can be recommended for theprivate practitioner.

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