An in vitro study of the effect of Pro Seal varnish on the shear bond strength of orthodontic brackets.

Aim: To compare the effect on the shear bond strength of orthodontic brackets when applying Pro Seal light-cure varnish to the enamel surface either before or after the application of sealant.

Methods: Sixty noncarious premolars were randomly divided into 3 equal groups. In groups I and 2, Pro Seal, a fluoride-releasing light-cure varnish, was applied to the enamel surface before or after, respectively, the sealant provided with the adhesive, while group 3 (control) was bonded regularly using only the sealant supplied with the adhesive. Mono-Lok 2 no-mix bonding system was used to bond stainless steel brackets to each tooth. All teeth were embedded in self-cure acrylic, placed in steel rings, and secured in a jig attached to the base plate of a universal testing machine. A perpendicular force was applied to the bracket at a crosshead speed of 0.5 mm/min. The residual adhesive on the enamel surface was evaluated after debonding with the adhesive remnant index.

Results: The mean shear bond strength for group 1, treated with Pro Seal varnish before the sealant, was 10.06 +/- 3.11 MPa. However, for group 2, where varnish was applied after the sealant, the mean shear bond strength was 12.78 +/- 3.7 MPa, while it was 12.81 +/- 2.6 MPa for the control group. An analysis of variance test showed that the mean shear bond strengths of the 3 groups were not significantly different. The chi-square test evaluating the residual adhesive on enamel surfaces showed no significant differences between all groups.

Conclusions: Application of Pro Seal before or after the sealant did not reduce the mean shear bond strength of orthodontic brackets. However, further studies are recommended to compare the amount of enamel protection offered in either situation.