Overview
What is it?
Antimicrobial photodynamic therapy (aPDT) combines a photosensitizing agent (commonly methylene blue or toluidine blue) with a specific wavelength of light to produce reactive oxygen species that kill bacteria.
How does it work?
A photosensitizer is applied to periodontal pockets where it binds to bacterial cells. When illuminated with light of the matching wavelength (typically 660–670 nm for methylene blue), the photosensitizer enters an excited state and transfers energy to molecular oxygen, generating singlet oxygen and free radicals that damage bacterial cell membranes and organelles.
When is it commonly used?
Used as an adjunct to SRP for chronic and aggressive periodontitis, peri-implantitis, and in endodontic disinfection. Applied immediately after mechanical debridement.
Mechanism of Action
The photosensitizer preferentially binds to bacterial cell membranes via electrostatic interactions (bacterial membranes are negatively charged). Upon light activation, the photosensitizer transitions to a triplet excited state and generates singlet oxygen (Type II photochemical reaction) or superoxide/hydroxyl radicals (Type I reaction). These reactive oxygen species cause oxidative damage to bacterial membranes, proteins, and DNA. The effect is localized and non-specific, reducing resistance risk.
Organisms Studied
| Organism | Abbr. | Research Finding |
|---|---|---|
| Porphyromonas gingivalis | Pg | Significantly reduced by methylene blue-mediated PDT as adjunct to SRP in clinical trials. |
| Fusobacterium nucleatum | Fn | Sensitive to PDT in both planktonic and biofilm forms. |
| Aggregatibacter actinomycetemcomitans | Aa | Reduced by PDT; some studies show effectiveness comparable to local antibiotics. |
| Tannerella forsythia | Tf | Reduced in clinical studies of PDT adjunct to SRP. |
| Candida albicans | Ca | PDT effective against Ca in oral candidiasis models. |
Evidence Summary
Benefits
- Broad-spectrum antimicrobial without resistance risk
- No systemic side effects
- Can be repeated safely
- Effective against biofilm-embedded bacteria
Limitations
- Effect is localized and short-term
- Requires specialized equipment (light source + photosensitizer)
- Added time and cost per visit
- Optimal protocols (dose, exposure time, photosensitizer concentration) not standardized
Quality of Evidence
Systematic reviews show modest adjunctive benefit over SRP alone, but studies vary in protocol and quality. Evidence is emerging.
Key Clinical Takeaways
- 1A safe adjunct with no resistance risk
- 2Benefits are modest and protocols need standardization
- 3May be particularly useful for patients with antibiotic allergies or resistance concerns
Evidence Meter
Early studies and pilot data show promise, but larger trials are needed.
Frequently Asked Questions
References
Antimicrobial photodynamic therapy in periodontitis: A systematic review and meta-analysis
Sgolastra F et al. (2013)
DOI: 10.1111/jcpe.12864Photodynamic therapy in periodontics: A systematic review
Azarpazhooh A et al. (2014)
DOI: 10.4103/0975-7406.163453Organisms Studied with This Therapy
Related Therapies
Educational use only. This page provides general information and does not recommend this therapy over others or provide medical advice. Always consult a licensed dental or medical professional for diagnosis and treatment decisions.