Comparative Efficacy of Photodynamic Therapy and Conventional Methods for the Disinfection of Clear Thermoplastic Sheets: An in Vitro Study Publisher

Summary: What best disinfects clear dental aligners? Lab tests found peroxide plus chlorhexidine beat photodynamic therapy against biofilms. #DentalCare #InfectionControl

Pourmousa L ; Mirhashemi A ; Keshvad M A ; Saberi S ; Sanaee Y ; Pourhajibagher M
Source: Frontiers in Dentistry Published:2026

Abstract

Objectives: This study compared the efficacy of photodynamic therapy (PDT) with that of conventional methods for disinfection of clear thermoplastic sheets used for the fabrication of aligners. Materials and Methods: In this study, 70 pieces of clear dental aligners measuring 15×15mm were gamma-sterilized, and randomly assigned to two groups (n=35) for inoculation with Streptococcus mutans and Lactobacillus acidophilus. After biofilm formation, the specimens were randomly assigned to 7 subgroups for disinfection with 0.2% chlorhexidine (CHX), 2.5% acetic acid, 3% hydrogen peroxide (HP), 100 µL/mL methylene blue (MB), PDT with MB and diode laser, diode laser alone, and distilled water (control). After sonication and culture, the colonies were counted and compared using ANOVA, Tamhane, and one sample t-test (alpha=0.05). Results: HP showed the highest efficacy in both bacterial groups (P<0.05). In S. mutans group, CHX had a significantly higher efficacy than the other modalities (P<0.05). Distilled water showed no significant difference compared with MB or laser (P>0.05), and acetic acid showed no significant difference compared with PDT (P>0.05). In the L. acidophilus group, CHX demonstrated significantly higher efficacy than the other modalities (P<0.05). Distilled water showed no significant difference compared with laser, and acetic acid showed no significant difference compared with PDT (P>0.05). Conclusion: Within the limitations of this in vitro study, PDT demonstrated moderate antibacterial activity against S. mutans and L. acidophilus biofilms. However, HP followed by CHX showed significantly greater antibacterial efficacy and remained the most effective disinfection approach among those evaluated. Copyright © 2026 The Authors.