Objective: Bond strength testing is a popular method to gain insight into the bonding of adhesive restorative materials. Bond strength tests usually are done to enamel or dentin, but not in combinations of the tissues, although this combination is the clinical norm. An improved in vitro simulation of clinical use requires integration of both dentin and enamel within a single restoration, but has not been previously considered. Therefore, the purpose of this study was to investigate the influence of enamel on bonding to dentin.

Methods: Freshly extracted (<6months) gamma radiation sterilized human third molars were sectioned to yield proximal specimens that were prepared to 320 grit roughness. Enamel (etched (K-Etchant Gel, Kuraray America, Inc.). and not-etched), dentin and surfaces integrating both enamel (~50%) and dentin within a single specimen (enamel - etch and not-etched) were used. Specimens were bonded with a self-etching adhesive bonding material (Clearfil SE, Kuraray America, Inc.) followed by a restorative composite (Z-100, 3M-ESPE). All specimens were bonded according to manufacturer's instructions, stored for 24 hours @ 37șC and100% RH prior to testing (Single Plane Shear Test) . The load for the enamel/dentin specimens was applied on the enamel to simulate the clinical situation. Specimens were examined by SEM to determine failure location. Results: SBS(MPa),N=6; Dentin=34.6±2.1; Enamel=31.9±3.5; Enamel/Dentin=31.2±2.9; Enamel(etched)=39.1±4.1*; Enamel(etched)/Dentin=32.6±4.4. (* significantly different, ANOVA and SNK P<0.05) All debonded specimens exhibited a mixed mode failure, but predominantly a cohesive failure through the adhesive layer.

Conclusion: The acid etched enamel group exhibited significantly higher bond strength than the others. Despite this, it was apparent from the fractured surfaces that the cohesive strength of the adhesive material was the limiting factor under the parameters of this study Supported by NIH/NIDCR GrantP01DE09859.

Back to the Dental Materials: I - Adhesion-Composite Bond Strength Program
Back to the IADR/AADR/CADR 82nd General Session (March 10-13, 2004)

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