Bond strength and interfacial micromorphology of compomers in primary and permanent teeth

Objectives. To (1) test and compare the shear bond strength of compomers (Compoglass, Dyract, Hytac) to primary and permanent dentin, (2) compare the values to those obtained with a resin-modified glass ionomer (Vitremer), and (3) evaluate the material–dentin interfacial morphology.
Sample and methods. The facial and lingual surfaces of 32 primary and 32 permanent teeth were used. The manufacturers' instructions were followed for the bonding procedures. After bonding, the teeth were thermocycled and sheared.
Results . ANOVA and Student-Newman-Keuls test revealed that the shear bond strength for Dyract was significantly higher than for the other restorative systems tested, both for primary ( P <0·001) and permanent ( P <0·01) teeth. Compoglass bond strength was significantly lower than Vitremer for the primary teeth dentin ( P <0·01). The shear bond strength for Compoglass to permanent dentin was significantly lower than for all other restorative systems ( P <0·001). There was a significantly higher shear bond strength for Compoglass ( P <0·05) and Dyract ( P <0·01) restorative systems for prim-ary compared to permanent teeth. For all products tested, all samples revealed cohesive failures. The highest frequency of cohesive failure was reported with Compoglass in both primary and permanent teeth and for Hytac and Vitremer in permanent teeth. Micromorphologically, all restorative systems revealed good adaptation to the underlying dentin; however, there was no evidence of the formation of a hybrid layer or deep resin penetration inside the dentinal tubules. There was no difference in the interfacial morphological adaptation between the primary and permanent teeth.
Conclusions . The compomers tested had shear bond strength values between those of resin-modified glass ionomers and resin composites.