An experimental study on the direct bonding method to reduce the risk of porcelain fracture

To evaluate resin-reinforced glass ionomer cement (RGIC) for bracket bonding to the enamel and porcelain surfaces employing the direct bonding system, the tensile and shear bond strengths of RGIC were measured. At the same time, the surfaces of the bonded materials were observed before the bond strength test. In addition, residual bonding agents on the bonded surfaces were investigated after the bond strength test to evaluate the bonding condition. The results were as follows:(1)The silane-treated porcelain surface was smooth, and no deposit was noted.(2)There was no significant difference in the tensile bond strength between the composite resin and RGIC.(3)The shear bond strength of composite resin was significantly greater than that of RGIC.(4)No significant difference was noted in tensile and shear bond strength between the porcelain and enamel.(5)The porcelain surface bonded using the composite resin was frequently destroyed after the shear bond strength test, indicating that it is desirable to load a tensile force during bracket removal.(6)The risk of destroying porcelain bonded with RGIC is low even when a tensile or shear force is loaded.(7)RGIC also showed favorable bond strength on porcelain, as well as on enamel, suggesting that its characteristics are clinically useful.