Systematic Review and Meta-Analysis of Shear Bond Strength after Photodynamic Therapy Versus Conventional Methods for Orthodontic Bracket Bonding

Abstract

Background: To systematically evaluate the effect of photodynamic therapy (PDT) on shear bond strength (SBS) of orthodontic brackets compared to conventional bonding methods through meta-analysis of in vitro studies. Materials and Methods: This systematic review and meta-analysis, following PRISMA guidelines, synthesized in vitro studies comparing the shear bond strength of orthodontic brackets following photodynamic therapy pretreatment versus conventional methods, utilizing a comprehensive, peer-reviewed search strategy across four databases up to December 2025. Random-effects meta-analysis was performed using Hedges’ g with 95% confidence intervals. Heterogeneity was assessed using I² statistic and Q-test. Subgroup analysis by photosensitizer type, sensitivity analysis, and publication bias assessment were conducted with subsequent trim-fill adjustments. Results: Eight in vitro studies comprising 13 PDT-control comparisons with 317 samples were included. Overall meta-analysis revealed significantly lower SBS for PDT groups compared to controls (Hedges’ g = -4.17, 95% CI: -6.350 to -3.361, P < 0.001). Substantial heterogeneity was observed (I² = 93.3%, Q = 166.645, P < 0.001). Subgroup analysis showed Methylene Blue PDT had the strongest negative effect (g = -5.795, P < 0.001), also Riboflavin PDT (k=3) demonstrated a significant negative effect (g = -3.54, P = 0.012). Mean SBS was 15.27 MPa for PDT groups versus 19.67 MPa for controls. Significant publication bias was detected (Egger’s test: P = 0.0003); while trim-fill justification remained significant in case of significantly lower SBS for PDT groups compared to controls. Conclusion: PDT, particularly with Methylene Blue photosensitizer, significantly reduces shear bond strength compared to conventional methods. Curcumin-based PDT shows more favorable bond strength profiles. Clinical application requires careful consideration of photosensitizer selection and bonding protocol optimization.