PHOTODYNAMIC THERAPY IN DENTISTRY

### Photodynamic Therapy in Dentistry

Photodynamic therapy (PDT) is a minimally invasive therapeutic approach that has emerged as a promising adjunct in modern dentistry, particularly for the management of microbial infections. PDT requires three essential components: a photosensitizing agent, a suitable light source, and molecular oxygen. When the photosensitizer is activated by light of an appropriate wavelength, it undergoes photochemical reactions that generate reactive oxygen species (ROS), including singlet oxygen and free radicals. These highly reactive molecules cause oxidative damage to microbial cell membranes, proteins, lipids, and nucleic acids, ultimately resulting in microbial inactivation and cell death.

The antimicrobial potential of PDT has led to its investigation across several dental specialties, including preventive dentistry, restorative dentistry, endodontics, periodontics, implant dentistry, and oral medicine. Commonly investigated photosensitizers include methylene blue, toluidine blue O, curcumin, and riboflavin. Depending on their chemical properties, these agents can preferentially interact with microbial cells and, following light activation, produce ROS with potent antimicrobial effects. The multifactorial oxidative mechanism of PDT is considered advantageous because it reduces the likelihood of microorganisms developing resistance through conventional antibiotic-resistance mechanisms.

In preventive and restorative dentistry, PDT has been investigated for the reduction of cariogenic microorganisms and residual bacteria within carious dentin. Its application may complement minimally invasive caries removal by reducing viable microorganisms that remain within the treated dentin. In endodontics, antimicrobial PDT (aPDT) has received considerable attention as an adjunct to conventional chemomechanical preparation. Root canal anatomy contains areas such as lateral canals, isthmuses, fins, and dentinal tubules that may harbor microorganisms beyond the direct reach of instruments. PDT may therefore provide additional microbial reduction following conventional instrumentation and irrigation. It has demonstrated activity against important endodontic microorganisms, including Enterococcus faecalis and Candida albicans.

In periodontal and implant therapy, PDT has been investigated as an adjunct to mechanical debridement for reducing pathogenic biofilms and improving local microbial control. Its localized action and limited systemic exposure make it particularly attractive for managing biofilm-associated infections.

Despite its potential, clinical application of PDT is associated with limitations such as restricted light penetration, photosensitizer concentration and staining, oxygen dependence, variable treatment parameters, and lack of standardized clinical protocols. Recent advances include nanoparticle-mediated photosensitizer delivery, targeted photosensitizers, natural photosensitizers, and optimized light-emitting diode and laser systems.

Overall, PDT represents a promising adjunctive technology for microbial control in dentistry. However, further well-designed clinical studies are required to standardize treatment parameters and establish its long-term clinical effectiveness.