The Impact of Antimicrobial Photodynamic Therapy (aPDT) with Various Photosensitizers on the Bond Strength of Orthodontic Brackets.

Introduction: Antimicrobial photodynamic therapy (aPDT) has demonstrated effectiveness in reducing gingival hyperplasia and preventing dental caries formation. However, concerns exist about its potential impact on the bond strength of resin composites. This study aimed to evaluate the effect of aPDT with various photosensitizers on the shear bond strength (SBS) of orthodontic brackets to enamel. Methods: A total of 102 healthy bovine central incisors were divided into six groups as follows: Group 1: control, Group 2: chlorhexidine (CHX), Group 3: aPDT with methylene blue and a 660-nm laser, Group 4: aPDT with indocyanine green and an 810-nm laser, Group 5: aPDT with curcumin and an LED, and Group 6: aPDT with riboflavin and an LED. Following the aPDT procedure, orthodontic brackets were bonded to the enamel surfaces. Shear bond strength was assessed using a universal testing machine, and the adhesive remnant index (ARI) scores were recorded. Data were analyzed using one-way ANOVA and Fisher's exact test, with a significance level set at P<0.05. Results: The highest SBS value was found in the indocyanine green group (10.31±3.46) and the lowest in the control group (7.82±1.86). ANOVA revealed no significant difference in shear bond strength between the groups (P=0.337). Additionally, the ARI scores showed no significant variation across the study groups (P=0.882). Conclusion: Photodynamic therapy does not adversely affect the bond strength of orthodontic brackets to enamel, and thus it can be applied safely in orthodontic patients due to its proven antibacterial benefits.