The shear bond strength of composite brackets on porcelain teeth

Recent advances in materials and techniques suggest that direct bonding of orthodontic attachments to surfaces other than enamel may now be possible. To test the effectiveness of bonding orthodontic attachments to porcelain teeth, composite brackets (Spirit MB) were bonded to 64 porcelain teeth by means of a self-cure non-mixed resin system (Unite). The 64 porcelain teeth were divided into groups of eight and after roughening with a green stone they were subjected to a combination of treatments. Some were etched, some primed with a silane coupling agent and some received both treatments before the brackets were bonded to them. Half of the teeth were then thermally-cycled 500 times between 4 and 60°C before all the brackets were removed in a shear test. The shear data was analysed by one way analysis of variance and the Student-Newman-Keul test. The results showed that the highest bond strength existed in the group which had been both etched and primed but not thermocycled (P < 0.05). The factors that affected the bond strength, beginning with the most significant, were acid etching, primer application, and then thermocycling. A mechanical based composite bracket can offer good bond strength to porcelain teeth.