Antimicrobial Photodynamic Therapy in Clinical Dentistry: Unravelling the Mechanisms and Exploring Hidden Benefits

Antibiotic efficacy, as a mainstay of therapy support in addressing bacterial infection, has witnessed a decrease due to the extensive and inappropriate use of these drugs; consequent efforts to find new methods to eradicate bacteria and combat multidrug resistance are intensifying. Antimicrobial photodynamic therapy (aPDT) has emerged as a notable alternative in view of the non-invasive nature of light, ease of application, and notably, the lack of potential resistance. Furthermore, the interactions and suppression of microorganisms upon exposure to reactive oxygen species (ROS) are key benefits of this therapy. The mechanisms of action of aPDT, influencing factors related to both the photosensitizer and the light delivery system, current challenges as well as new technologies-strategies for overcoming them, have been thoroughly discussed. Until today, there are no clear recommendations regarding the applied aPDT protocol, and this may be attributed to the multifactorial nature of this treatment and the complexity of incorporating advanced mathematics, physics, and optical technologies into clinical practice. Thus, the aim of paper #1 was to critically evaluate the recorded parameters of laser aPDT applications in clinical dentistry through a systematic review of randomized clinical trials. It has been suggested that aPDT significantly enhances tissue healing. Following the application of the photosensitizer to the target tissue, the incident light scatters beyond the intended area, leading to a secondary therapeutic effect known as photobiomodulation (PBM), which promotes healing and repair in surrounding tissues. The mechanisms of action and the beneficial effects of this therapy have been extensively examined. Specifically, paper #2 is the first systematic review of PBM's effects on periodontal ligament stem cells, highlighting its potential to enhance proliferation and osteogenic differentiation for periodontal regeneration. Hence, a comprehensive understanding of the optical properties of both the photosensitizer and the target tissue is paramount to achieving predictable treatment outcomes. Understanding light distribution is essential in determining the light parameters used during aPDT to optimize beneficial outcomes for both the target and surrounding tissues. As light penetrates through the photosensitizer, it may induce additional beneficial PBM effects in the surrounding environment. Therefore, a thorough understanding of light propagation is vital for developing effective aPDT protocols that exploit the dual benefits of antimicrobial action and photobiomodulation. The spectrophotometric analysis performed as part of this thesis in paper #3, illustrates the light attenuation through various photosensitizers and highlights the potential combined beneficial effects of aPDT and PBM. Calculated fluences are proposed and future studies should prioritize evaluating these proposed fluences for each photosensitizer to thoroughly assess and validate the beneficial effects of photomedicine.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2024

Author dc:creator

• Mylona, Vasiliki

Licence

• https://dora.dmu.ac.uk/bitstreams/9658d1b4-d271-4043-97e3-526e0249948f/download