Photodynamic therapy (PDT) is an oxygen dependent photochemical reaction that occur upon light mediated activation of a photosensitizing compound leading to generation of cytotoxic reactive oxygen species.PDT has emerged in recent years as a non-invasive therapeutic option.Many photosensitizers like methylene blue, toluidine blue has proven to be effective. But certain disadvantages linked to these agents, such as, incidental staining, need to purchase of separate laser units etc., establish the need for a potential new photosensitizer transcending these disadvantages.A Food and Drug Administration (FDA) dye, Indocyanine green (ICG) was used in hepatic function diagnostics, fluorescent angiography in ophthalmology and later in cardiology had become established as new in dentistry.A new photosensitizer called indocyanine green (ICG) has been developed which gets activated upon absorbing light of specific wavelength. The fact that ICG does not require oxygen can make it even more effective in anaerobic subgingival area as compared to other photosensitizers and used for the treatment of periodontitis.The disadvantages of earlier dyes, better efficiency and safety with ICG and successful in vitro studies using this dye against periopathogenic bacteria, led to present studies.

Not many studies have been conducted using ICG dye to study effect of aPDT in periodontitis.Not many studies have been conducted to compare the clinical and microbial efficacy between ICG and methylene blue.

The present study helps to evaluate the clinical and microbiological effects of ICG mediated aPDT as an adjunct to non-surgical management of chronic periodontitis.