Objective: The aim of this study was to assess self-ligating brackets on dry enamel and contaminated human blood enamel, tested in 3 different moments of the bonding procedures: before the adhesive application, after the adhesive application, before and after the adhesive application.
Method: 400 inferior permanent bovine incisors were randomly divided into 20 groups of 20 specimens; 320 brackets (Step Leone, Smart Clip 3M Unitek, Quick Forestadent, Damon Ormco) and 80 buttons (Leone) were bonded. Shear bond strength (SBS) was recorded using an Instron machine and statistically analyzed by ANOVA. The enamel surface of all teeth and brackets bases were evaluated with an optical microscope and the quantity of remaining adhesive was estimated by ARI index. The chi-square test was used to determine significant differences in the ARI scores among the different groups.
Results: Damon, Step brackets and lingual buttons showed significant higher SBS than Smart Clip and Quick brackets on dry enamel. On the contrary, all groups showed a significant reduction of shear bond strength on contaminated enamel and no significant differences in the SBS was found among the different contaminations. The ARI index in dry enamel condition had a significantly higher frequency of “1” and “2”; whereas in blood contaminated enamel the ARI index had a significantly higher frequency of “0” and “1”.
Conclusions: Smart Clip, Damon brackets and lingual buttons showed higher shear bond strength than Step and Quick brackets in dry condition; in blood contamination no significantly differences of SBS were found among them.