Comparison of Shear Bond Strength of Metal Brackets Bonded to Porcelain Surface using Different Surface Conditioning Methods: An in vitro Study

Abstract

To evaluate and compare the shear bond strength of metal brackets bonded to ceramic surfaces using different conditioning methods and to assess the site of bond failure after debonding. A total of 70 ceramic surfaces were produced with uniform shape, size and composition. The samples were divided into 7 groups (each of 10 samples). Group 1 was the control group (untreated surface); in group 2 the surface were roughened with a diamond bur; in group 3 the surface were etched with hydrofluoric acid; in group 4 the surfaces were sandblasted; in group 5 the surfaces roughened with bur and silane applied; in group 6 the surfaces were etched with hydrofluoric acid and silane applied and in group 7 the surfaces were sandblasted and silane applied. To all the above groups, metal orthodontic brackets were bonded with light cure adhesive. The brackets were later stored in artificial saliva and incubated at 37°C (24 hours). The samples were then subjected to shear bond strength test using an Instron universal testing machine. The debonded porcelain surfaces were then studied under stereomicroscope to assess site of bond failure. Sandblasting the ceramic surface and silane application showed the highest bond strength. Stereomicroscope examination after debonding showed that the bond failure is at bracket-adhesive interface in four groups namely hydrofluoric acid, sandblasting, hydrofluoric acid with silane and sandblasting with silane. Sandblasting with silane combination produced the highest shear bond strength, so it is a clinically suitable method for bonding orthodontic metal brackets onto ceramic surface. Bonding orthodontic brackets to ceramic crowns of patients has been a tough task. In this study, different conditioning methods were used to treat the ceramic surfaces before bonding. The results showed that sandblasting the ceramic surface prior to application of silane produced the highest shear bond strength which is clinically suitable to reduce bond failures.