Does chlorhexidine affect the shear bond strengths of orthodontic brackets?

Background/purposeThe 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 methodsIn 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.ResultsGroup 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.ConclusionsCHX gel is thought to obviate initial caries lesions during fixed orthodontic treatment.