Does chlorhexidine affect the shear bond strengths of orthodontic brackets?

Abstract Background/purpose The purpose of this study was to examine the effect of 1% chlorhexidine (CHX) gel on the shear bond strength (SBS) of orthodontic brackets bonded with Transbond XT (XT, 3M Unitek) and Transbond Plus Self-Etching Primer (TSEP, 3M Unitek). Materials and methods In total, 75 extracted premolars were collected and randomly divided into five groups of 15 teeth each. Brackets were bonded to teeth using a different experimental technique for each group as follows: (I) (control): etch/dry/Transbond XT; (II) CHX gel/etch/dry/Transbond XT; (III) etch/dry/CHX gel/Transbond XT; (IV) dry/TSEP; and (V) CHX gel/dry/TSEP. All products were used according to the manufacturers’ instructions. An Instron Universal Testing Machine was used to directly apply an occlusal shear force onto the enamel-bracket interface at a speed of 0.5 mm/min. Residual adhesive on each tooth was evaluated using an adhesive remnant index (ARI). Analysis of variance was used to compare the SBS of the groups, and a Chi-squared test was used to compare ARI scores. Results Group I had the highest mean SBS (16.47 ± 4.2 MPa), followed by Groups II (16.24 ± 4.5 MPa), III (13.08 ± 4.50 MPa), IV (11.95 ± 2.7 MPa) and V (11.16 ± 2.8 MPa). No statistical differences were observed between Groups I and II (P > 0.05) or between groups IV and V (P > 0.05). However, SBS scores for Groups IV and V were significantly lower than those of Groups I and II (P > 0.05). No significant difference was observed in ARI scores among any of the groups (P > 0.05). Prior application of CHX gel did not significantly affect the SBS of orthodontic bonding adhesives. Conclusions CHX gel is thought to obviate initial caries lesions during fixed orthodontic treatment.