Orthodontic bonding to porcelain surfaces: in vitro shear bond strength

purpose: to evaluate in vitro the shear bond strength of orthodontic accessories to porcelain, under different porcelain surface treatment protocols, and the resultant failure pattern after debonding. methods: the sample consisted of 80 feldspathic porcelain discs, divided into 4 groups: group 1 - 37% phosphoric acid etching; group 2 - 10% fluorhydric acid; group 3 - 37% phosphoric acid and silane application; group 4 - 10% fluorhydric acid and silane application. the samples were submitted to the shear bond strength test in a universal test machine to record the maximum rupture force. results: group 1 showed lower results, and group 4 presented higher results than the other tested groups.there was no statistical difference between groups 2 and 3. groups 1 and 3 presented exclusively adhesive failures between porcelain and resin, whereas groups 2 and 4 showed cohesive failures in porcelain. conclusion: the use of phosphoric acid followed by silane application was the best protocol for bonding orthodontic accessories to porcelain surfaces, since it was capable of resisting the forces applied during orthodontic treatment without causing irreversible failures in restorations.