Improvement of Antibacterial Potency of Riboflavin Mediated Photodynamic Therapy by Potassium Iodide Against Aggregatibacter Actinomycetemcomitans Biofilm Formed on Orthodontic Miniscrews: An in Vitro Study Publisher Pubmed



Jafarieh D ; Jafarieh R ; Bahrami R ; Pourhajibagher M ; Bahador A
Source: Photodiagnosis and Photodynamic Therapy Published:2025

Abstract

Background: This study investigated the effect of potassium iodide (KI) on the antibacterial efficacy of riboflavin-mediated photodynamic therapy (PDT) against Aggregatibacter actinomycetemcomitans biofilms formed on orthodontic miniscrews. Materials and Methods: The minimum inhibitory concentration (MIC) of riboflavin was 200 μg/mL. Biofilms were grown on orthodontic miniscrews and divided into ten groups (n = 6): PBS (negative control), 0.2 % chlorhexidine (CHX; positive control), LED, KI, PDT with riboflavin at ½ MIC (100 μg/mL), ¼ MIC (50 μg/mL), and ⅛ MIC (25 μg/mL), and the same PDT conditions combined with 100 mM KI. Biofilm viability was assessed by colony-forming unit (CFU) counts. Results: All treatments significantly reduced CFU/mL compared with PBS (P < 0.001). The addition of KI enhanced the antibacterial effect of riboflavin-mediated PDT at sub-MIC concentrations, with the strongest effect at 25 μg/mL riboflavin + KI (P = 0.001 vs. riboflavin alone). CHX and PDT with 100 μg/mL riboflavin + KI showed the highest inhibition, with 97.56 % and 95.12 % reductions, respectively. Notably, PDT with 50 μg/mL riboflavin (¼ MIC; LED 450 ± 5 nm, 1000–1400 mW/cm², 60–80 J/cm², 1 min) plus 100 mM KI achieved an antibacterial effect comparable to 0.2 % CHX. Conclusion: PDT mediated with riboflavin at 50 μg/mL combined with KI effectively reduced A. actinomycetemcomitans biofilms formed on orthodontic miniscrews. © 2025 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. http://creativecommons.org/licenses/by-nc-nd/4.0/