Effect of applying chlorhexidine antibacterial agent on the shear bond strength of orthodontic brackets

The purpose of this study was to determine whether the application of chlorhexidine as an antibacterial agent affects the shear bond strength and debonding failure modes of orthodontic brackets. Thirty-six recently extracted human premolars were cleaned and randomly assigned to one of three groups: prophylaxis with pumice only prophylaxis using a 13,500 ppm fluoridated pumice, and prophylaxis with pumice followed by application of 0.12% chlorhexidine paste. All teeth were etched with a 37% phosphoric acid gel and metal orthodontic brackets were bonded to each tooth using the same bonding system. The teeth were mounted in phenolic rings and stored in deionized water at 37 degrees C for 72 hours. A Zwick Universal Testing Machine was used to determine shear bond strengths. The residual adhesive on the enamel surfaces was estimated using the Adhesive Remnant Index. The analysis of variance was used to compare the various groups. Significance was predetermined at P < 0.05. The results indicated that there were no significant differences in bond strengths between the chlorhexidine-, fluoride-, and nonfluoride-treated teeth (P = 0.233). The Chi-Square test evaluating the residual adhesive on the enamel surfaces also showed no significant differences (P = 0.456) between the various groups. In conclusion, the use of chlorhexidine and/or fluoride prophylactic pastes does not significantly affect shear bond strength nor bond failure location of orthodontic brackets.