Effect of Pretreatment with Fluoride, Chlorhexidine, and Mixed Fluoride-Chlorhexidine Gels on Shear Bond Strength of Orthodontic Brackets: An Ex-Vivo Study

Background and Aim: Orthodontic patients are at an increased risk of caries due to difficulty in plaque control. Antimicrobial agents, such as fluoride and chlorhexidine, can be useful in preventing tooth demineralization. The present study aimed to determine the effect of fluoride and chlorhexidine gels and their mixture on the shear bond strength (SBS) of orthodontic brackets. Materials and Methods: In this ex-vivo study, 70 premolars were divided into seven groups. The first group was considered as the control. The second, third, and fourth groups were first etched with 37% phosphoric acid and then pretreated with chlorhexidine, fluoride, and fluoride-chlorhexidine gels, respectively. The brackets were then bonded. In the fifth, sixth, and seventh groups, the enamel surface was etched after pretreatment, and then, the brackets were bonded. After mounting the teeth, SBS was measured using the Instron machine. Data were analyzed using one-way analysis of variance (ANOVA) and Tamhanechr('39')s T2 test (α≤0.05). Results: The mean SBS was 19.7 MPa in the control, 11.1±2.5 MPa in the second, 11.8±3.6 MPa in the third, 21±7.5 MPa in the fourth, 19.4±9 MPa in the sixth, and 14.1±6.7 MPa in the seventh group with no statistically significant differences. However, there was a statistically significant decrease in the mean SBS (8±5.2 MPa) of the fifth group (chlorhexidine before etching) compared to the control group (P=0.04). Conclusion: The use of fluoride and chlorhexidine can be recommended to orthodontic patients because of antibacterial and anticaries properties and no significant decrease in the SBS of orthodontic brackets (except when chlorhexidine is used before etching).