The effect of enamel air abrasion on the retention of bonded metallic orthodontic brackets

The purpose of this study was to compare the conventional acid-etch techniq ue with an air abrasion surface preparation technique. Eighty freshly extra cted noncarious human premolar teeth were randomly divided into the followi ng 4 groups: (1) acid etched with 37% phosphoric acid for 15 seconds (Expre ss Dental Products, Toronto, Canada), (2) sandblasted with 50 mu aluminum o xide by a microetcher (Danville Engineering Inc, Danville, Calif), (3) poli shed with pumice followed by acid etched with 37% phosphoric acid for 15 se conds, (4) sandblasted with 50 mu aluminum oxide by a microetcher followed by acid etched with 37% phosphoric acid for 15 seconds. All the groups had stainless steel brackets (Dentaurum, Standard Edgewise) bonded to the bucca l surface of each tooth with no-mix adhesive (Express Dental Products, Toro nto, Canada). A Lloyd testing machine (Lloyd Instrument LR 30K; Segensworth West, Foreham, UK) was used to determine tensile bond strengths at a cross head speed of 0.5 mm/sec. The mean bond strength values of these are as fol lows: the only sandblasted group was 38.05 +/- 9.93 N; the only acid-etched group was 62.72 +/- 11.44 N; the group that was polished with pumice follo wed by acid etched was 69.78 +/- 14.87 N; and the group that was sandblaste d followed by acid etched was 89.31 +/- 13.34 N. The statistical analysis w as done by an analysis of variance and Scheffe test. The sandblasting follo wed by acid etching group had significantly higher bond strength values whe n compared to the other 3 groups, This study showed that sandblasting shoul d be followed by acid etching to produce enamel surfaces with comparable bo nd strength. The current findings indicate that enamel surface preparation using sandblasting with a microetcher alone results in a significantly lowe r bond strength and should not be advocated for clinical use as an enamel c onditioner.