Effect of treatment frequency on the efficacy of superhydrophobic antimicrobial photodynamic therapy of periodontitis in a wistar rat model

Superhydrophobic antimicrobial photodynamic therapy (SH-aPDT) is advantageous wherein airborne singlet oxygen (¹O₂) is delivered from a device tip to kill a biofilm with no photosensitizer exposure and no bacterial selectivity (Gram + or Gram -). For effective treatment of periodontitis, the frequency of treatment as well as the optical light fluence required is not known. Thus, we sought to determine whether single or repeated SH-aPDT treatments would work best in vivo using two fluence values: 60 and 125 J/cm². We assessed the efficacy of three protocols: single treatment; interval treatments (days 0, 2, and 7); and consecutive treatments (days 0, 1, and 2). After 30 days of evaluation, we found that, SH-aPDT in 3 consecutive treatments significantly decreased Porphyromonas gingivalis levels compared to single and interval SH-aPDT treatments, as well as SRP-chlorhexidine (CHX) controls (p < 0.05). Notably, clinical parameters also improved (p < 0.05), and histological and stereometric analyses revealed that consecutive SH-aPDT treatments were the most effective for promoting healing and reducing inflammation. Our study shows what works best for SH-aPDT, while also demonstrating SH-aPDT advantages to treatment of periodontitis including no bacterial selectivity (Gram + or Gram -) and preventing the development of bacterial resistance.