PEDIATRC DENTISTRY/Copyright © 1982 byThe American Academy of Pedodontics/Vol. 4, No. 1

Cast anterior bridges utilizing composite resin

Gerald E. Denehy, DDS, MS

J. he loss of a permanent anterior tooth on ayoung patient poses unique problems in replacementfor the pedodontic practitioner. Full crown coverageof the abutment teeth necessary for conventionalfixed bridgework is often contraindicated due to thelarge size of the pulp chamber and the potential forpulpal damage. Even if possible, this reductionviolates the current concepts of good conservativedentistry, since these teeth rarely have caries orrestorations.

The care necessary for proper maintenance of a fullcoverage fixed bridge may often be neglected by ayoung patient, and dislodgement or damage is morepossible during the accident prone years. As the pa-tient ages, increased exposure of the clinical crownsof teeth also occurs, decreasing the esthetics of thegingival margins of anterior full coverage crowns.

Most young patients therefore, have missinganterior teeth replaced by a removable appliance,often of the "flipper" type. Although these ap-pliances are conservative, they are often damagingto the supporting tissues of the teeth and an incon-venience to the patient.

The new composite resin systems, in combinationwith the acid-etch procedure, have offered the prac-titioner a wide range of esthetic techniques for thesolution of anterior teeth problems.13 One of these isa conservative, relatively inexpensive, and perma-nent method of replacing missing anterior teeth withlittle or no tooth structure removal.4The techniqueinvolves bonding a thin cast metal framework withporcelain pontic to the lingual surface of the anterior

abutment teeth utilizing the acid-etch technique withcomposite resin as the bonding agent.

The use of acid-etch retained cast appliances hasalso been expanded to include applications other thananterior tooth replacement. These include posteriortooth replacement,5 postorthodontic stabilization,6

periodontal splinting,7 and tooth recontouring.8

Clinical ProceduresThe anterior acid-etch retained cast bridge normally

requires two patient appointments with appropriateintervening laboratory time. The first appointmentshould involve a careful analysis of the patient'smouth to determine suitability for treatment. Aswith any restorative treatment, proper case selectionis essential to ensure success (Figures 1 and 2).

Considerations of proper principles of design andsupport normally used with traditional fixed appli-ances should also apply to acid-etch retained castbridges. Excessively long spans or periodontally com-promised abutment teeth are definite contraindica-tions. For an acid-etch bridge to be successful, suffi-cient enamel surface area must be present to provideadequate retention. Abutment teeth with short clini-cal crowns, lingual surfaces abraded into dentin, orlarge restorations are contraindicated.

Approximately one millimeter of clearance spacein occlusion is necessary to provide adequateframework thickness. In limited clearance situations,this may often be achieved by selectively removing0.5mm of enamel from both the lingual fossa of theabutment tooth and the incisal edges of the oppos-

Figure 1. Maxillarythree-unit acid-etch re-tained cast bridge —facial preoperativeview. Patient was18-year-old male withabsence of lateral in-cisor due to partialanodontia. Patient wascurrently wearing aremovable appliance.

Figure 2. (right) Lingual preoperative view showing intact enamel surfaces.

44 CAST ANTERIOR BRIDGES/COMPOSITE RESIN: Denehy

ing mandibular teeth. Direct incisal forces on the pon-tic should be minimized, although the pontic may bekept in incisal function.

Once the dentist has determined that the case isappropriate for treatment, with sufficient spaceavailable, the teeth should be pumiced and a detailedimpression made of the arch using an elastic impres-sion material.

Selection of the shade for the pontic should takeinto account the degree of translucency of the incisaledge of the abutments. Shade variations and incisal"bluing" will result from metal reflection throughtranslucent abutments. Minimal incisal extensionwith the framework and the use of an opaquer maybe necessary when this problem is anticipated. Aftershade selection the patient may be dismissed.

The impression is poured in die stone and an outlineof the framework drawn on the model (Figure 3).

Figure 3. Stone working cast with framework outline.

Coverage of the lingual surface of the abutment teethshould be maximal with the retainer margins ter-minating proximally on the marginal ridges andsupragingivally just inside the crest of curvature toprevent over contouring. Care should be taken tominimize incisal show of metal from either the con-nectors or the retainers.

The framework is constructed with thin metalplates over the lingual surface of the abutment teeth,the mechanical retention placed in the metal. Theplates should be 1/2 to 3/4 mm thick and taper downto knife-edge margins. The connector bars joining thepontic to the plates should be located in a positionto facilitate patient cleaning, and should have enoughstrength and rigidity to prevent metal fatigue. Ifmultiple abutments are utilized, the connectorsshould be located at the contact area between theadjacent teeth to maintain the gingival embrasurespace. Retention in the framework is achieved by theplacement of six to eight round holes approximately1.0mm in diameter in each retainer. The holes shouldbe spaced in a manner that will not jeopardize thestrength of the connector bar. A porcelain adaptable,non-precious alloy is recommended for frameworkconstruction because of its rigidity and low cost.

The pontic may be made of any laboratory adaptedesthetic material. Porcelain is recommended,however, because of its excellent esthetics anddurability. Construction of acid-etch retained castanterior bridges is available at many commercial den-tal laboratories (Figure 4).

Figure 4. Cast anteriorbridge with porcelainpontic showing reten-tive holes.

The second appointment with the patient involvesthe try-in and attachment of the appliance. Thebridge is carefully checked for color, contour, and fit.Occlusion is checked in centric and excursive move-ments. A loop of dental floss may be used to hold theappliance in place while checking fit and incisal rela-tionships (Figure 5).

Color change due to metal reflection through trans-lucent abutment teeth becomes much more apparentwhen the bridge is seated with the resin. If a colorchange is suspected, the bridge may be trial seatedwith the unmixed universal filled resin. This shouldbe done before etching, and both the tooth and frame-work should be cleaned following the trial seating.If discoloration is apparent, a composite resinopaquer should be used on the inside surface of theframework when attaching the bridge.

When the appliance is ready for attachment, thelingual and proximal surfaces of the abutment teethare thoroughly pumiced (Figure 6). After rinsing, theteeth are isolated with cotton rolls and gauze to pre-vent contamination, then air dried. An etching solu-tion of phosphoric acid is applied to all surface areasto be covered with the framework. The teeth are etched

Figure 5. Dental floss used to support cast bridge duringtry-in for fit, function, and esthetics.

PEDIATRIC DENTISTRY: Volume 4, Number 1 45

Figure 6. Enamel sur-faces to be etchedcleaned with pumice.

for sixty seconds, rinsed for twenty seconds, airdried, and reisolated.

A self-polymerizing composite resin system is usedto attach the appliance. Although a commerciallyrecommended system11 works well, any of the self-polymerized systems containing both filled and un-filled resins may be used.

The unfilled resin is mixed for fifteen seconds,applied to the etched enamel surfaces (Figure 7), andthe excess blown off with air. The filled resin is nextmixed and applied in a thin layer to the inside sur-face of the appliance retainers (Figure 8). The ap-pliance is immediately seated in place using fingerpressure to insure stability. An explorer may be usedto clear the gingival embrasures of excess resin if careis taken not to disturb the framework (Figure 9).

The resin is allowed to polymerize undisturbed forsix minutes. The framework should then be carefullyexamined for deficiencies in the retentive holes or theperipheries. If any discrepencies are noted, additionalfilled resin should be added and polymerized beforefinishing procedures are initiated.

Polymerized excess resin is removed using conven-tional composite-resin finishing instruments such asfinishing burs and discs (Figure 10); care must betaken to remove all excess in the gingival embrasureareas. Any metal surfaces scratched during finishingprocedures should be repolished. The finished frame-work should exhibit composite resin only in the reten-tive holes (Figures 11 and 12). Before dismissal,the patient should be given thorough home-careinstructions. "Comspan, The L. D. Caulk Co., Milford, DW.

Figure 9. Explorerremoving excess filledresin while framework

securely stabilizedisduring polymerizationof filled resin.

The appliances should be checked for looseness atroutine recall examinations. If any looseness is noted,the entire appliance should be removed and reattached.All residual composite resin on the abutment teethmust be removed and the framework cleaned beforereattachment. Careful analysis and correction of thereason for dislodgement should be made before theappliance is replaced.

DiscussionOver two-hundred and fifty acid-etch cast appli-

ances have been placed with excellent results at TheUniversity of Iowa College of Dentistry over the pastseven years. Cases have ranged from single toothreplacement to eleven unit appliances with five pon-tics. Dislodgements have been few in number andspecific cause can usually be found for bondingfailures. The majority of these cases have been reat-

Figure 10. Sandpaper disc used to remove excess resin fromframework.

Figure 7. Unfilled resinapplied to etchedenamel surfaces ofabutment teeth.

Figure 8. (right) Castbridge with filled resinready for insertion.

46 CAST ANTERIOR BRIDGES/COMPOSITE RESIN: Denehy

Figure 11. Maxillarythree-unit acid-etch re-tained cast bridge —facial postoperativeview.

Figure 12. Three unitbridge — lingualpostoperative view.

tached and are currently functioning satisfactorily.Although the acid-etch cast appliances have shown

excellent retention, they still present the option ofreversibility. If crown lengthening is necessary as thechild grows older, the bridge may be removed, porce-lain added to the pontic and the bridge reattached.Removal is also easy in the event of orthodontictreatment.

The procedure is relatively atraumatic, requiringno anesthesia and minimal chair time — both impor-tant factors for the pedodontic patient. Since the costof the procedure is approximately one-third to one-half that of a conventional bridge, parents readilyaccept it.

Finally, the conservative service provided the pa-tient is maximal in terms of tooth tissue relationship,esthetics, and pulpal vitality of the abutment teeth.

Dr. Denehy is professor, department of operative dentistry, Univer-sity of Iowa College of Dentistry, Iowa City, Iowa 52242. Requestsfor reprints should be sent to him.

1. Fuller, J. L. The acid-etch technique as a substitute for or-thodontic treatment. Quint Internat 4:49, 1977.

2. Denehy, Gerald E. and Fuller, James L. Use of the acid-etchtechnique to improve anterior esthetics. Dent Surv 51:34,1975.

3. Chalkley, Yvonne. Clinical use of anterior laminates — construc-tion and placement. JADA 101:485, 1980.

4. Howe, Donald F. and Denehy, Gerald E. Anterior fixed par-tial dentures utilizing the acid-etch technique and a cast metalframework. J Prosthet Dent 37:28, 1977.

5. Livaditis, Gus J. Cast metal resin-bonded retainers for posteriorteeth. JADA 101:926, 1980.

6. Rochette, A. L. Attachment of a splint to enamel of loweranterior teeth. J Prosthet Dent 30:418, 1973.

7. Reinhardt, J. W., Denehy, G. E., and Chan, K. C. Acid-etchbonded cast orthodontic retainers. Am J Orthod 75:138,1979.

8. Thayer, K. and Doukoudakis, A. Acid-etch canine riser occlusaltreatment. J Prosthet Dent 46:149, 1981.

Quotable QuoteWith respect to nutrients, what is an inappropriate level of intake? All nutrients, of course, are required

in the human diet at some minimum level in order to satisfy a wide variety of bodily functions. But we arenow beginning to recognize that an excessive intake of nutrients may be harmful. When evaluating the effectsof nutrients on the risk of cancer, we should attempt to identify the optimum intake — within some range— that produces the most beneficial nutritional results while minimizing the risk of cancer. One emerging con-cept is that those levels that optimize such traditional nutritional effects as healthy growth are the same levelsthat minimize cancer risk. We now know that inappropriately low intakes of some nutrients may cause anenhancement of the cancer process, whereas with other nutrients inappropriately high intakes create the sameresult.

From: Campbell, T. Colin: "The web ofhunger-more is not necessarily better,"

Natural History 90(5) May, 1981.

PEDIATRIC DENTISTRY: Volume 4, Number 1 47