Shear bond strength of metallic brackets bonded with a new orthodontic composite

Aim: The aim of this study was to assess the shear bond strength of orthodontic brackets in different enamel surfaces using the Transbond Plus Color Change composite (TPCC-3M Unitek), and to analyze the Adhesive Remnant Index (ARI). Methods: Seventy-two human premolars were divided into six groups (n = 12), as follows: Group 1(control) - Transbond XT conventional; in Groups 2 to 6, TPCC was used under the following enamel treatment conditions: phosphoric acid and XT-primer; Transbond Plus Self-Etching Primer (TPSEP); phosphoric acid only; phosphoric acid, XT-primer and saliva; and TPSEP and saliva, respectively. Twenty-four hours after bonding, the brackets were debonded with an Instron machine at a crosshead speed of 0.5 mm/min, and ARI was evaluated by using a stereoscopic magnifying glass. Results: The mean shear strength values (MPa) for Groups 1 to 6 were 24.6, 18.7, 17.5, 19.7, 17.5 and 14.8, respectively. Data were submitted to ANOVA and Tukey’s test (α = 0.05). Group 1 had significantly higher shear bond strength values than Groups 3, 5, and 6 (p < 0.05), but did not differ significantly from Groups 2 and 4 (p > 0.05). No statistically significant differences (p > 0.05) were found between Groups 2, 3, 4, 5 and 6. Conclusions: Bracket bonding using TPCC showed adequate adhesion for clinical use, and the type of enamel preparation had no influence.