Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemotherapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. In recent years, PDT has been introduced as an important novel disinfection therapy in the field of implant dentistry. The inactivation of microorganisms using PDT has been defined as antimicrobial PDT. PDT has the potential to be an alternative of antibiotics, especially for the treatment of localized infections and oral biofilm. PDT is unlikely to cause bacterial-resistance and is equally effective against antibiotic-resistance and antibiotic-susceptible bacteria.

Inconsistent results have been reported regarding the potential role of PDT as an adjunct to mechanical debridement in the management of peri-implant infection. Thus, the aim of the present trial is to investigate the treatment effect of non-surgical treatment with and without photodynamic therapy on initial peri-implantitis.

Inclusion Criteria:

1. Male and female subjects, ages over 18.
2. Subjects with at least one implant with initial peri-implantitis: PPD of 4-6mm combined with BOP+, bone loss of 0.5-2mm on peri-apical radiographs compared to the time point of restoration placement.
3. Availability for the 12 month duration of the study.
4. Good general health (ASA classification I-II).
5. Signed Informed Consent Form.

Exclusion Criteria:

1. Medically compromised subjects (ASA classification III-V)
2. Pregnant or lactating females.
3. Peri-implant mucositis defined as the absence of radiographic marginal bone loss between restoration placement and pre-screening review.
4. Subjects treated for >2 weeks with any medication known to affect soft tissue condition (e.g. phenytoin, calcium antagonists, cyclosporin, Coumadin and non-steroidal anti-inflammatory drugs) within 1 month of the baseline examination.
5. Unwilling to participate in the study.