Effect of different surface treatments (mechanical and chemical) on the repaired bond strength of a laboratory composite

Abstract

The aim of this in vitro study was to compare the effects of two mechanical surface preparation techniques, including air abrasion and Nd:YAG laser, with the use of two self-etch and etch-and-rinse adhesive systems on the repair bond strengths of laboratory composite. Materials and methods: One hundred fifty cylindrical samples of laboratory composite (Gradia), measuring 4 mm in height and 6 mm in diameter, were prepared. The samples were randomly divided into 6 groups (n=25). In groups 1-3 the composite resin surfaces were prepared, respectively, as follows: no mechanical roughening, mechanical roughening by air abrasion and roughening by Nd:YAG laser, followed by application of Single Bond etch-and-rinse adhesive. In groups 4-6 the preparation techniques were respectively the same as those in groups 1-3, followed by application of Clearfil SE Bond self-etch adhesive. Subsequently, direct Gradia composite was bonded to the prepared surfaces as a repair material in all the groups. Repair bond strength values of the samples were measured and the fracture patterns were determined in all the groups. In addition, surface topography and micro-structure were evaluated after application of mechanical preparation techniques using a scanning electron microscope and atomic force microscope in selective samples. Data were analyzed with two-way ANOVA and a post hoc Tukey test at a significance level of P<0.05. Results: The mean repair bond strength value was significant based on the preparation technique used (P<0.001), i.e. in the air abrasion and Nd:YAG laser groups repair bond strength values were significantly higher than those in no-preparation groups (P<0.0005). In addition, there were significant differences in repair bond strength values between the air abrasion and Nd:YAG laser groups, with significantly higher values in the air abrasion groups (P<0.0005). However, there were no significant differences in repair bond strength values between the adhesive systems used (P>0.05). Furthermore, the cumulative effects of the adhesive system and the surface preparation technique were not significant (P>0.05). Conclusion: Surface preparation of laboratory composite resin with air abrasion and Nd:YAG laser resulted in a significant increase in repair bond strength, with air abrasion being more effective in this respect. However, there were no significant differences in bond strength between etch-and-rinse and self-etch adhesive systems