Influenza dei restauri estetici sulla cementazione adesiva dei bracket

Direct or indirect bonding of orthodontic brackets on previously restored anterior teeth must ensure clinically satisfactory adhesion forces to a surface that is often composed of a micro-filled composite resin. Being chemically passive because of its permanence in the oral cavity, this surface must be prepared to restore ideal conditions for bracket bonding. This study examines the effectiveness of polishing with rubber cup and abrasive paste in surface preparation before orthodontic bonding. Specimens of microfilled composite resin (Gradia Direct) and human enamel have been polished with fine silicon cups and Prisma-gloss extrafine paste; a standard bracket for upper central incisor has been bonded to these specimens by direct (Transbond XT system) or indirect (Transbond XT, Sondhi Rapid-set) technique. Adhesion forces have been evaluated with shear bond test. The values measured were lower than the clinically acceptable interval of 6-8 MPa for indirect technique on polished composite. Statistical analysis with ANOVA, Tukey and Student’s T tests showed significant differences between enamel and composite as well as between direct and indirect techniques: the most effective adhesion has been found on enamel with direct technique.