Evaluation of the ceramic/ceramic interface

The purpose of this study was to investigate bond strength for ceramic orthodontic brackets bonded to dental porcelain. The following factors were tested. Two types of ceramic brackets were placed on two different types of porcelain surfaces with two different bonding systems. Three different debonding techniques, and various composite removal techniques and surface restoration techniques were used. Two hundred porcelain samples were used that duplicated the labial surface of a maxillary right central incisor. Bond strengths were measured with an Instron Universal testing machine (Instron Corp., Canton, Mass.). Mean bond strength and standard deviations were calculated and significance was determined with analyses of variance (ANOVA) and a chi-square test. Composite removal and polishing methods were investigated by scanning electron microscopy. The results showed that tensile type debonding methods are the least likely to damage the porcelain surface. Some brackets (Unitek Corp., Minn.) having a higher bond strength (p < or = 0.01) fractured the porcelain surface when tested in the shear debonding mode. The bonding materials tested were comparable to adhesion studies of similar brackets to enamel. The Ormco primer-Concise porcelain bonding system was significantly stronger (p < or = 0.01) than the Scotchprime-Transbond. Composite removal by careful use of a carbide bur, followed by the use of the Shofu porcelain adjustment kit and porcelain glaze polish, restored the finish to a normal porcelain surface after debonding. The study showed that shear and tensile debonding forces for glazed porcelain with the use of silane primer, were comparable with those reported in the literature for enamel, thus clinically sufficient. At the same time, preservation of the glaze allowed an almost ideal polishing of the porcelain surface after debonding.