Direct bonding to porcelain: an in vitro study.

Three different force strengths were tested to investigate the effect of Fusion in direct bonding of brackets to porcelain. The resistance values of shear, tensile, and rotation strength forces are acceptable in the range of forces commonly used in orthodontics. The mean shear strength had greater resistance values to breaking than two other groups. The roughness of glazed porcelain and the fit of brackets to contoured porcelain teeth seems to be of great importance in the bonding effects. The role of Fusion in direct bonding is comparable to that of other sealants which are commonly being used in direct-bonding systems. It is claimed that Fusion creates a chemical bond with acrylic or composite resins to porcelain. The technique could be summarized as follows: (1) Glaze is removed in the area which is supposed to be bonded directly. (2) Fusion is applied over the roughened surface. (3) Acrylic or composite resin is mixed and applied on the mesh part of brackets. (4) The bracket is pressed against the porcelain teeth by moderate pressure until final polymerization.