Effect of water contamination on the shear bond strength of self-ligating brackets

Purpose: The aim of the present study is to evaluate the effect of water contamination on the shear bond strength (SBS) and adhesive remnant index (ARI) score of self-ligating brackets. Materials and methods: One conventional bracket and three different self-ligating brackets were bonded onto 160 bovine permanent mandibular incisors, divided randomly into 8 groups. For each type of bracket, 20 samples were bonded on dry enamel and 20 after water contamination. After 24 h, all specimens were tested for SBS using an Instron Universal Testing Machine, and ARI scores were evaluated. Results: All groups showed clinically adequate SBSs. Quick brackets bonded onto dry enamel showed significantly higher SBSs than all other groups tested, whereas the lowest shear strength values were recorded for Step, Quick, and Damon 3MX brackets bonded onto contaminated enamel and for Damon 3MX onto dry enamel. Frequency distribution of ARI Scores showed a prevalence of ARI “2” and “3” for all the groups tested. Conclusions: Water contamination reduces the SBS of self-ligating brackets, but significant differences have been found only for Quick brackets. All groups showed a significant higher frequency of ARI Score of “2” and “3”.