[ effect of different tooth surface preparation methods on microshear bond strength]

ABSTRACT

Evaluation of new adhesives efficacy in bonding orthodontic brackets to enamel has led to different results. The new measuring method, micro-shear bond strength, is preferred as an accurate method due to its ability to reduce confounding factors.The purpose of this study was to evaluate and compare the micro-shear bond strength of three different adhesive systems for enamel surface preparation before bracket bonding.In this experimental study, 90 extracted premolars were randomly divided into three groups of 30. Transbond XT was bonded to enamel after enamel surface preparation with acid etch in the first [control] group, Transbond plus self-etch primer in second group, and Adper prompt L-pop self-etch adhesive in third group. Then each group was randomly divided into two subgroups of 15. Micro-shear bond test was performed after 24 hours [T1] and 3-months [T2]. Bond failure mode was also evaluated according to Adhesive Remnant Index [ARI]. Two way ANOVA and Tukey tests were used for bond strength evaluation in groups, and mode of bond failure was analyzed with Kruskall Wallis and Mann Whitney tests.The highest bond strength was found in acid etch group [29.17 MPa]. Difference of bond strength at two intervals was statistically significant in all groups [p <0.001]. Bond strength difference between T1 and T2 was also significant in three groups [p <0.001]. However changes over time in three groups did not reveal any significant differences [p = 0.091]. Bond failure analysis demonstrated significant differences in ARI between groups.Bond strength of acid etch group was the highest and self etch primer showed higher bond strength than self etch adhesive group. Less adhesive remnant was found in self etch group