Effect of Pre-etching and Thermocycling on Self-etching Adhesive Enamel Bonding

Objective: The purpose of this study was to evaluate pre-etching (PE) with phosphoric acid (PA) and thermo-cycling (TC) on the enamel shear bond strength (SBS) of a self-etching adhesive system on ground enamel. Materials and Methods: Human teeth were embedded in phenolic rings using methylmethacrylate resin and the enamel surfaces were ground flat to a 600 grit surface and divided in 4 groups (n=10): Group A – PA pre-etch and self-etching primer (Panavia 21 OP, Kurray America, NY); Group B – PA pre-etch and self-etching primer and TC; Group C – self-etching primer; Group D – self-etching primer and TC. In groups A and B, the teeth were etched for 30 seconds with 40% PA (Panavia Etching Agent V, Kurray America), rinsed, re-etched for 30 seconds and rinsed again. Metal rods of Rexillium III (Pentron, San Diego, CA), 3.8 mm in diameter were particle abraded with 50 micron aluminum oxide, and bonded to the ground enamel surfaces with 2 Kg pressure using Panavia 21 OP. Specimens were stored in distilled water for one week at 37˚C. Groups B and D were thermo-cycled between baths of 5±2˚C and 55±2˚C for 5000 cycles. Specimens were loaded to failure at a crosshead speed of 1 mm/min. Mean values were analyzed with a two-way ANOVA (factors PE and TC). Results: No effect was shown for either PE (p=0.062) or TC (p=0.859) or the interaction of PE and TC (p=0.651). Values for SBS (Mean MPa and SD) were: Group A – 21.8 (4.5); Group B – 22.3 (4.3); Group C – 19.2 (5.8) and Group D – 18.1 (6.7). Conclusions: There was not a statistically significant difference (p>0.05) between any of the groups but a tendency toward better bond strengths with the phosphoric acid pretreatment was seen. Thermo-cycling did not significant affect SBS.