Assessment of Antimicrobial Photodynamic Therapy With Curcumin on the Shear Bond Strength of Orthodontic Bracket: An In Vitro Study.

Background: Antimicrobial photodynamic therapy (aPDT) is a noninvasive treatment approach that eradicates a broad variety of harmful microorganisms. This study aimed to examine the impact of aPDT with curcumin on the shear bond strength (SBS) of orthodontic bracket to enamel. Materials and Methods: In this in vitro study, 45 intact human premolars were randomly divided into three groups (N = 15): the control group, aPDT group with curcumin 500 mg/L, and aPDT group with curcumin 1000 mg/L. After performing aPDT, the orthodontic brackets were attached to the surface of the teeth and then samples were thermocycled for 3000 cycles. The brackets were then debonded using a universal testing machine. The SBS and adhesive remnant index (ARI) were calculated. Data were analyzed in SPSS25 software. ANOVA with post hoc tests was used to compare SBS among groups. Results: The findings of this study indicated that the aPDT with curcumin 500 mg/L showed the highest SBS mean, while the control group had the lowest. The average SBS difference between the control group and the curcumin 500 mg/L group as well as the curcumin 1000 mg/L group was statistically significant (p  < 0.05). However, the difference between the average SBS of the two curcumin groups was not statistically significant (p = 0.184). The experimental groups using curcumin had a considerably higher ARI value compared to the control group (p ≤ 0.001). However, this index was not statistically different among the C₅₀₀ and C₁₀₀₀ groups (p  > 0.05). Conclusions: aPDT with curcumin increases the ARI and the bond strength of the orthodontic brackets and can be used as an effective method to reduce microbial plaque and inflammation before bonding in orthodontic patients.