The effect of air abrasion preparation on the shear bond strength of an orthodontic bracket bonded to enamel.

The purpose of this study was to determine the method of preparation of enamel which best retains a bonded orthodontic bracket against a shear force. Two hundred and twelve human lower premolars were randomly divided into four equal groups. Group 1 underwent no air abrasion, group 2 received treatment with 25 microm aluminium oxide particles, group 3 with 50 microm particles, and group 4 with 100 microm particles. All groups were treated with a self-etching primer before bonding of an orthodontic bracket. Each tooth was tested in a JJ Lloyd M30K machine to determine the maximum shear force required to dislodge the bracket from the tooth. A one-way analysis of variance test conducted at a 95 percent confidence level (CL) demonstrated that there was a significant difference (P < 0.01) with respect to the four methods of preparation of the enamel surface. An unpaired t-test was then applied at a 95 percent CL. There was no statistically significant difference between groups 1 and 2. There was, however, a statistically significant difference between groups 1 and 3 (P < 0.01), as well as between groups 1 and 4 (P < 0.01). In addition, there was significant difference found between groups 2 and 3 (P < 0.05), groups 2 and 4 (P < 0.01), and groups 3 and 4 (P < 0.05).