Operative Dentistry

The "sandwich" technique as a base for reattachment of dentalfragmentsLuiz Narciso Baratieri* / Sylvio Monteiro, Jr* / Mauro Amaral Caldeira de Andrada*

Esthetics and function were restored to a fractured maxillary central incisor by reat-taching the tooth fragment with the "sandwich" technique (glass-ionomer cement andcomposite resin). After 3 years, the toolh showed optimal fragment rehydration, pres-ence of pulped vitality, absence of sensitivity, and a di.screte color alteration in the ¡inebetween the fragment and tlie dental remnant. (Quintessence Int 1991:22:81-85.)

Introduction

The "sandwich" technique, first advocated by McLeanet al,' has been widely discussed and accepted foruse iu various clinical situations.'"™ Tbe techniquecombines the favorable properties of glass-ionomercements—adhesion to dental structures, release of flu-oride ions to the dental structures adjacent to the res-toration (anticaries action), better biologic compati-bility, and responsiveness to acid etcbing—witb thefavorable properties of composite resins—superiorwear resistance, greater cohesive strength, and bettertranslucency.' The combined restoration thus is moreesthetic and offers better-sealed margins.'

Tbe fact that glass-ionomer cements are responsiveto add etching,''"'" through which a porous surfaceis created by a selective wearing of its matrix,' is im-portant to the physicoehemical bonding between com-posite resins and the dental structures, particularly ifthe enamel of the cervical margin is of a poor qualityor nonexistent.^ Mechanical te,sts have shown that thebond strengtb between composite resin and acid-etched glass-ionomer cement is greater tban thecohesive strength of the cement by itself.'•''•*•"

Associate Professor. Department of Operative Dentistry, FederalUniversity of Santa Catarina. School of Dentistry, Av OsmarCunha, No. 15 Bloco A Conjunto 4Ü2, 88000 Florianópolis,Santa Catarina, Brazil.

Several techniques, including the acid-etching/fluidresin/composite resin technique, have been suggestedto enhance the stability and/or to improve the estheticresults of the reattachment of a tooth fragment to afractured anterior tooth.-* '̂'-"" This paper presents aelinical case in which a tooth fragment was reattachedto the coronal remnant with the sandwich technique.The advantages and limitations of the procedure willalso be discussed.

Case report

A 20-year-old woman hit her maxillary incisorsagainst a windowsill. fracturing tootb 11. Tbe patientlooked for a dentist itnmediately after the accident,taking the tooth fragment (not in water) with her. Shewas seen by a practitioner who carried out emergencytreatment, applying a calcium hydroxide cement plusa zinc oxide-eugenol cement to the dentin for pro-tection. The dentist referred the patient to us tn thatcondition (Fig 1). Shestillhad the tooth fragment withher. and it was still not in water (Fig 2).

Wben tbe patient came to our office, 1 day after thefracture had occurred, our ftrst action was to immersethe fragment in ajar of water. A routine examinationwas performed, and a periapical radiograph was takento evaluate the possibihty of root involvement (theroot was not involved). Next, the emergency dressingwas removed to evaluate the extent of the fracture.The fragment was repositioned against the tooth rem-nant to check its adaptation. Loss of facial tooth

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Fig 1 Incisai view ot a wide coronai fracture. The emer-gency coating (calcium hydroxide cement and zinc oxide-eugenoi cement] has aiready begun to separate.

Fig 2 (left) Paiatai view ol the dental fragment reveals theexposure of the inner surface of enamei. (right) Facial viewot the dental fragment shows the white incisai region, thearea hit by the patient.

Fig 3 Once the fragment is back in its piace, loss of faciaidental structure is found, particulariy near the cervical mar-gin.

Fig 4 Once the fragment is back in its place, no loss otpalatai dentai structure is found. The fragment has sufferedfrom dehydration, so it is whiter than the coronai remnant

Figs The giass-ionomer cement coating, after the fieldwas isolated and the exposed dentin was cleaned with 25%poiyacrylic acid for 10 seconds, washed with an air-waterspray, and air dried.

Fig 6 Phosphoric acid gei is applied to the surface of theglass-ionomer cement, to the inner enamel, and to ap-proximately 2 mm of surface enamei (30-second etch).

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Fig 7 Phosphoric acid gel is appiied to the inner surfaceof the fragment and to approximately 2 mm of the externaisurtace |30-second etch).

Fig 8 Enamei and glass-ionomer cement after acid etch-

structure next to the cervical margin (Fig 3) and goodpalatal adaptation (Fig 4) were verified.

The field was tsolated wtth a rubber dam, prophy-laxis of enamel was performed with a slurry of pumiceand water, and the exposed dentin was cleaned withair-water spray and air dried. Exposed dentin was thencoated with a film of fast-setting glass-ionotner ce-meut (Ketac-Boud, ESPE GtnbH) (Fig 5). After 8minutes of dentinal protection with the glass-ionotnercement, the fragment was again positioned andchecked for adaptation. To restore the adaptation be-tween the fragment and the coronal remnant, part ofthe inner dentin of the fragment had to be groundaway with a spherical diamond bur.

Approximately 2 mm of surface enamel, all the frac-tured enamel, and the glass-ionomer cernent surfacewere acid etched with a phosphoric acid gel for 30seconds (Fig 6). The tooth remnant was rinsed withan air-water spray for 1 minute and air-dried. Boththe outer and inner surfaces of the fragment receivedthe same treatrnent (Fig 7). The enamel of the frag-ment and the coronal remnant offered, following acidetching, a dull, white aspect (Figs 8 and 9)-

The fragment was then bonded to the tooth rem-nant. A thin layer of fluid resin (Concise Enamel BondSystem, 3M Dental Products Div) was first applied tothe etched enamel of the fragment and to the surfaceof the glass-ionomer cement, as well as to the etchedenamel of the coronal remnant. Before the fluid resinset, the fragment was loaded with a paste-paste com-posite resin system (Concise) and attached to the co-ronai remnant- Excess resin was removed with an ex-

ploratory probe. The fragment was held in positionwith a gutta-percha rod for 8 minutes.

The dam was removed and the occlusion checked.Finishing and polishing of exposed composite resin atthe facial region was carried out with flexible sequen-tial disks. The patient was cautioned about a possiblefragment detachment, and instructed not to allowforceful incisor function.

Results

Immediate results (Fig 10) indicated that there wouldbe long-term success. Clinical exatnination 60 daysafter the reattachment revealed a totally rehydratedfragment, acceptable esthetics and satisfactory func-tion (Fig 11). The 3-year examination revealed thatesthetics and function had been maintained (Fig 12).Pulpal vitality was observed both at the initial andsubsequent exarns. No kind of sensitivity was reportedby the patient pos tope ratively. Radiographs indicatedapical normality.

Discussion

The possibility of employing the sandwich technique'for the reattachment of a dental fragment representsa breakthrough in the art and science of such resto-rations, particularly for those cases in which enamelis nonexistent or minimal at the cervical margin. Acidetching of the glass-ionomer cement surface favors theformation of microporosities,"''"-^ which lead to astrong union between the composite resin and the ce-

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Fig 9 Internal surface ot the fragment after acid etching,Tbe fragment is field in place with a gutta-percha rod.

Fig 10 Clinical view immediately following reattacfimentoftbe fragment and removal of tbe rubber dam, Tbe degreeof debydration of restored tooth can be noticed when it iscompared to the opposing teetb.

Fig 11 Clinical view 6 months after reattachment Fig 12 Clinical view 3 years after reattachment.

,17 jfjj. strength of this union is greater thanthe cohesive strength of the cement itself.'"" The pro-cedure also allows, indirectly, the chemical bonding ofthe composite resins to the dental strticture,' thus re-sulting in better-sealed margins.

The reported case shows the possibihty of applymgthe sandwich technique to the reattachtnent of a dentalfragment. However, there are possible difficulties, suchas the requirement that the cement layer have a min-imal thickness of 0,5 mm to favor the formation ofmicro porosities.' To produce that effect, a greateramount of dentin will have to be ground from thefragment, to compensate for the thickness of the ce-ment layer and make possible the readaptation of thefragment to the dental remnant. This could be detri-mental to the iong-tenn esthetics of the restoration,'

Another criticism of the technique is the need towait at least 20 minutes after agglutination before acidetching the surface of a glass-ionomcr cement. Un-timely etching might cause an exaggerated, nonselec-live wearing of the cement matrix,' ' Such a delay, nec-essary for the maturation of the cement matrix, couldrender the technique unproductive, because a dentist'stime is usually precious and, thus, substantially ex-pensive. Nevertheless, "sacrificing" such time to pro-duce a better-sealed, more esthetic, and longer-lastingrestoration would be fully justified.

At the time we decided to proceed with the reat-tachment as described above, we were not aware oftbe work by Smith,'' which indicated that the etchingof glass-ionomer cernent surfaces must not exceed 20seconds. Nevertheless, it is our behef thiu »i-c suppos-

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edly excessive (30-second) etching of the glass-ionornercement has not apparently affected the efficacy ofeither the protection offered by the cement or the reat-tachment bond. The tooth has shown vitality at recallexaminations, the patient has not reported any sen-sitivity, and the fragment has not been dislodged.

When bond strength between a glass-ionomer ce-ment and a composite resin is studied, silane couplingagents should also be considered because these"primers" might produce a clinical reaction hetweenthe two materials,'* Recently, new formulations ofglass-ionomer cements have been introduced, in whicha resin matrix forms an essential part of the compo-sition. It is claimed that these materials require noetching to achieve a bond with composite resins,'^Such materials could improve, in the near future, thestability of sandwich restorations.

The decision not to adopt any kind of chamfer oneither the fragment or tooth remnant is due to a recentwork by Dean et al,-° in which they concluded thatthere were no differences in the fracture strengths ofFragments that received no mechanical preparationand those prepared with a 45-degree chamfer beforereattachment.

The final esthetics of such restorations might changefrom case to case, particularly beeause of differencesin the degree of dehydration presented by the frag-ment, the loss of dental structure, the number of frag-ments, and the technique employed in preparing andreattaching the fragment,' In the majority of patients,the fragment will be totaUy rehydrated within 1 weekfollowing reattachment; nevertheless, rehydrationmight take a few months,'^ or might not even happenat all.̂

References

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14, Amir E, et al; Restoration of fractured immature maxillarycentral incisors using the crown fragments, Pediatr Dent1986;8:285-288,

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