New type metal bracket for suppression of resin remaining in debonding

A new type of metal bracket was prepared to minimize the destruction at the bracket-resin interface and to suppress resin from remaining on the tooth surface in debonding. The brackets were made of stainless steel and had a modified cylindrical outward shape (phi 3.8 mm x 1.8 mm), twin-type wings, and a 0.018 inch (0.457 mm) slot. Retentive forces and debonding aspects of residual resin for the brackets were studied using three representative adhesives. The mean tensile strengths at the bracket-resin interface were over 80 kgf/cm2 for all three resins. As the quantitative evaluation for the residual resin condition, a resin remaining ratio (RRR) was adopted. The aspects of the residual resin differed according to the type of adhesive resin used. Almost no resin was detected on the tooth surface just below the central part of the bracket, and even for the peripheral part which did not have an effective resin retention form, the RRR was under 30% for the heavily filled resin.