Bonding Performance of Etch-and-Rinse and Universal Adhesives for Metal Bracket Fixation: An In Vitro Mechanical and...

Background: Durable adhesion between orthodontic brackets and enamel is essential for successful fixed orthodontic therapy. Despite simplified adhesive systems being available, conventional etch-and-rinse adhesives remain widely used due to their reliable enamel bonding. Methods: This in vitro study evaluated the bonding performance of three orthodontic adhesive strategies in combination with Transbond XT composite resin for metal bracket fixation. Thirty extracted human premolars were randomly allocated to three groups according to the adhesive system applied: OptiBond Solo Plus (etch-and-rinse method), SafeBond Universal DC (selective enamel etching method) and Transbond XT primer (control method). Shear adhesion resistance, maximum force and breakout force were measured and statistically analysed. Results: No statistically significant differences were observed between the OptiBond and SafeBond groups for any of the evaluated mechanical parameters (p > 0.05), although the OptiBond group exhibited higher mean values. The Transbond XT primer group showed significantly lower adhesion resistance and debonding forces than both of the other groups (p < 0.05). SafeBond demonstrated lower variability of results compared with OptiBond. Conclusions: When used with Transbond XT composite resin, both OptiBond Solo Plus and SafeBond Universal DC provided comparable mechanical performance for metal bracket bonding. While OptiBond yielded higher mean bond strength values, SafeBond exhibited more consistent behaviour. The Transbond XT primer alone resulted in inferior bonding performance.