Bond-strength and morphological interface between dentine and auto-adhesive cements

Objectives: Evaluate Bond strength and the morphological interface between auto-adhesive luting cements, human dentin and indirect resin composite. Methods: The oclusal enamel of 16 human molars was removed using a low-speed saw. The medium dentin exposed was ground with Sic (600grit). Indirect composite resin discs(Sinfony, 3M-ESPE) were confectioned and were sandblasted with 50µm aluminum oxide particles, and bonded to dentin surfaces, according to manufacture's instructions with the following auto-adhesive luting cements: Rely X U100 (3M-ESPE), Maxcem (Kerr), BisCem (Bisco) and MultilinK Splint (Ivoclar/Vivadent) After 24-hour water storage (37^o C), each tooth was sectioned in X and Y directions to obtain twenty 0.8 ± 0.1mm² cross-sectional area sticks. Specimens were tested in tension with an Instron at cross-speed of 0.5mm/min. Statistical analysis included ANOVA and Tukey test. The surfaces of 8 dentine discs (1.5mm thick) were treated with each of the auto-adhesive cements and bonded to form disc-pairs for SEM analysis. Results: (Mean MPa±S.D.) RelyX U100: 21.5±5.95; Maxcem: 5.3± 2.11; BisCem: 5.4±3.25 and Multilink Splint: 10.1±3.39. U100 resulted in statistically higher bond strength values than all other cements (p=0.00001). Fracture pattern analysis in SEM revealed predominance of cohesive cement fractures for U100 and adhesive for Maxcem, BisCem and Multilink Splint cements. RelyX U100 showed continuous interaction with underlying dentin as resin tags infiltrated into the dentinal tubules. No hybrid layer formation was observed. Other cements revealed discontinued regions at the dentin-cement interfaces. Conclusions: The U100 cement presented morphological dentin interaction and higher bond strength than all other cements.

Supported by CNPq PQ 310845/06-8.