Comparisons of two approaches for removing excess adhesive during the bonding procedure

The purpose of this study was to compare the effects on shear bond strength of removing excess adhesive from around the bracket base at 2 time periods : (1) immediately after placing the bracket on the tooth, and (2) after sub jecting the adhesive to 5 seconds of light curing to initially secure the b racket in its proper position, The debonding forces were evaluated at 2 tim es; within half an hour after bonding and after storing for 24 hours in wat er at 37 degrees C. These comparisons will help determine the most advantag eous time for the clinician to remove excess adhesive from around the brack ets during the bonding process, The teeth were randomly divided into 4 grou ps according to: (a) the time of removal of the excess adhesive from around the bracket base namely; immediately after placing the bracket or after 5 seconds of light curt: and (b) the time of debonding the brackets, namely w ithin half an hour or after 24 hours. Shear bond strength was measured usin g a Zwick test machine and calculated in Megapascals. The results of the an alysis of variance (F = 35.05) comparing the 4 experimental groups indicate d the presence of significant differences between all 4 groups (P = .0001). In general, the shear bond strengths were significantly larger for the 2 g roups debonded after 24 hours, whether they were light cured for a total of 40 seconds ((X) over bar = 8.8 +/- 3.6 MPa) or 45 seconds ((X) over bar = 6.9 +/- 3.4 MPa). On the other hand, the shear bond strengths was significa ntly lower in the 2 groups debonded within half an hour from their initial bonding, whether light cured for 40 seconds ((X) over bar = 0.4 +/- 1.0 MPa ) or 45 seconds ((X) over bar = 3.4 +/- 2.7 MPa). In conclusion, the additi onal 5 seconds of light cure significantly increased the initial shear bond strength. On the other hand, removing excess adhesive after 5 seconds of l ight cure significantly decreased the shear bond strength at 24 hours.