The Effect of Peri-Bracket Excess Adhesive on Shear Bond Strength and Enamel–Adhesive Interface Morphology With Confocal Laser Scanning Microscopy: An In Vitro Comparative Study

Abstract

Aim: To evaluate the effect of leaving excess adhesive around orthodontic brackets on the shear bond strength and on the enamel–adhesive interface characteristics. Materials and Methods: One hundred forty four human premolars were randomly divided into two groups according to the test performed. For the shear bond strength, 120 teeth were bonded with stainless steel orthodontic brackets using Transbond XT light cure adhesive composites. After positioning the bracket and before light curing, excess adhesive was removed according to the test group: group 1, all excess adhesive was removed (0 mm excess); group 2, 1 mm excess adhesive was left; group 3, 2 mm excess adhesive was left; shear bond strength was measured immediately and after three months of natural aging using a universal testing machine; and adhesive remnant index scores were also evaluated. For the enamel–adhesive interface characteristics, 24 teeth were bonded with stainless steel orthodontic brackets using Transbond XT light cure adhesive composites mixed with Rhodamine B fluorescent dye, excess adhesive was removed in the same manner according to the test groups, and teeth were evaluated using confocal laser scanning microscopy. Results: Time did not significantly affect the bond strength results ( P = .888) but the amount of excess adhesive significantly affected the results ( P < .05). Interaction terms were not significant ( P = .337). In both immediate and aged conditions, group 1 (0 mm excess) presented the highest bond strength results (MPa; P < .05). No significant difference was found in adhesive remnant index scores or enamel–adhesive interface characteristics. Conclusion: Excess adhesive around orthodontic bracket does not increase shear bond strength.