An In Vitro Comparison of Shear Bond Strength Between Two Orthodontic Light-Curable Adhesive Pastes

Abstract

Background and Objectives: A relatively new light-cure orthodontic adhesive BracePaste® can fluoresce under UV light to assist in cleaning up excess flash after bonding. Complete removal of excess resins around the bonded brackets may minimize excessive loss of enamel upon debonding. The objective of this study was to determine the shear bond strength of BracePaste compared to that of the conventional “Transbond XT” adhesive. Additionally, enamel and bracket interfaces were examined to determine the location of bond failure and the tooth surfaces were visually examined to assess severity of enamel marks and the presence of remaining adhesives on the enamel. Materials and Methods: A sample of 84 extracted human premolars were randomly divided into two groups. Group 1 (control) metal twin brackets were bonded with the Transbond™ XT composite resin; Group 2 brackets were bonded with Bracepaste ® composite resin. All samples were etched with 37% phosphoric acid, rinsed with distilled water, dried, applied with a layer of Assure Plus resin, and then composite resin. All bonded brackets were placed in a thermocycler for 24 hours cycling between baths of 5oC and 55oC. After thermocycling, brackets were debonded with an Instron machine simulating and calculating debond shear force. The bracket and tooth were examined under 10x magnification to determine the adhesive remnant index (ARI) value and Visual Index scale was used to measure enamel marks on teeth after finishing and polishing. Two independent sample t tests were used to compare the difference in mean SBS between groups. Exact Mantel-Haenszel chi-square analysis was conducted to assess the association between ARI value and group. We considered statistical significance for all tests with a two-sided p-value of ≤0.05. Results: There was no significant difference in mean SBS between the teeth bonded with Transbond XT or BracePaste . No significant differences were found in the ARI scores between the 2 groups using either the 4 point or 6 point scoring systems. There was no significant difference in adhesive remnants left after polishing between the 2 groups of brackets. Conclusions: BracePaste resin possessed similar SBS to Transbond XT resin and both are able to withstand occlusal forces during orthodontic treatment. The addition of the UV light system with the new composite resin did not compromise the bond strength or result in more enamel defects after debonding and finishing.