DIRECT BONDING TO PORCELAIN

Orthodontic brackets were bonded to 180 faces of 45 porcelain cubes th at were divided into three groups according to their surface preparati on. In group I, the glaze had been removed with a sandpaper disk, wher eas in group II, it was maintained. A solution of acidulated phosphate fluoride (APF) gel was applied to the samples in groups I and II for 5 minutes after pumicing, in group III, the glaze had been removed wit h a coarse diamond bur. Each group was further divided into four subgr oups, depending on whether a priming agent had been used, and the type of composite used to bond the brackets, Shear force was used to debon d the brackets, and the results showed that the APF solution was unabl e to provide enough retention on porcelain surface to bond brackets. M echanical retention, obtained with a coarse diamond bur, was necessary to increase bond strength, which can be further improved by chemical bonding, with a silane priming agent. Therefore bonding to porcelain i s clinically possible and is an acceptable procedure in orthodontic tr eatment.