الفهرس | Only 14 pages are availabe for public view |
Abstract The present study was designed to evaluate in vitro the shear bond strength of a multi-mode adhesive resin cement when bonded to enamel and dentin in different application modes and to assess the morphological characterization of the tooth/adhesive interface microscopically. A total of 40 sound extracted human permanent anterior teeth and 40 extracted molar teeth were used in this study. Anterior teeth had their labial surface ground to obtain flat enamel surfaces and embedded into the acrylic resin with their labial surfaces facing upwards, Molar teeth had their occlusal surfaces ground to expose flat dentinal surfaces and they were embedded into the acrylic resin with their occlusal surface facing upwards. Each substrate specimens were then divided into four groups of 10 specimens each according to resin cement applied: RelyX Ultimate in total-etch mode, RelyX Ultimate in self-etch mode, Variolink II total-etch resin cement and Multilink Automix self-etch resin cement. A thin walled plastic tube, was placed over the surfaces and the resin cements were built up following manufacturer’s instructions. Specimens were secured to the universal testing machine and the shear load was applied at a constant cross-head speed of 0.5mm/min, then shear bond strength was calculated in MPa. The fractured surfaces were observed with a stereomicroscope for assessment of the ARI which has a range between 0 and 3 which is assigned according to the following criteria; 0 = No adhesive left on the tooth, 1 = Less than half of the adhesive left on the tooth, 2 = More than half of the adhesive left on the tooth, 3 = All the adhesive left on the tooth. Three specimens from each group after shear bond strength test were sectioned, air-dried, gold-sputtered and then observed by SEM. The resintooth interfaces were photomicrographed to be evaluated. The results were recorded, tabulated, and statistically analyzed. 79 When bonded to enamel, the studied cements showed a statistically significant difference with P<0.001. RelyX Ultimate in total-etch mode and variolink II showed the highest mean values. On dentin, studied cements showed non-significant difference with P=0.053. An etching step prior to RelyX Ultimate cement yielded higher shear bond strength values on enamel and dentin. The difference in mean values of ARI scores between studied cements were statistically significant with P<0.001 on enamel and P=0.022 on dentin. There was also a significant positive correlation between shear bond strength with ARI scores. Interfacial morphology of etched specimens showed thin resin tags penetrating into enamel. On dentin RelyX Ultimate in total-etch mode showed better interface morphology and improved tag length compared to respective self-etch counterpart. It was concluded that the multi-mode adhesive resin cement (RelyX Ultimate) has to be applied in the total-etch mode when bonded to enamel, while for dentin both self-etch and total-etch modes could be applied with improved penetration pattern in the total-etch mode. Higher shear bond strength values did correlate with higher ARI scores and the length of resin tags formed by total-etch adhesives seems not to play an important role in determining bond strengt |