Comparative evaluation of antimicrobial effect of indocyanine green and methylene blue dye as photosensitizers for photodynamic therapy as an adjunct to scaling and root planing in patients with moderate periodontitis - A randomized controlled trial

Ø  The primary goal of periodontal therapy is to eliminate bacterial biofilm and endotoxins from root surfaces of the teeth. However, owing to anatomical variations in root surfaces, complex furcation areas, concavities on root surfaces, and bacterial invasion of the surrounding soft tissues, nonsurgical periodontal therapy (NSPT) alone cannot eliminate periodontal pathogens.1

Ø  Although systemic and local administration of antibiotics into periodontal pockets may be effective for disinfection, the frequent usage of antibiotics bears the potential risk of producing resistant microorganisms.1

Ø  In recent years, photodynamic therapy (PDT) with the help of lasers has been used to decontaminate the pocket environment as it is a minimally invasive treatment that activates the immune system, has low systemic toxicity, and possesses high bactericidal properties. The eradication of tissue invasive microorganisms associated with periodontitis and peri-implantitis by lasers has been amply demonstrated.2

Ø  Combining lasers and photosensitizing agents can result in photo destruction of target cells due to cytotoxic effect in the presence of oxygen. This light-induced effect is due to the conversion of the excited photosensitizer from the ground state to the triplet state resulting in production of singlet oxygen and other reactive agents, which are very toxic to certain cells or bacteria.3

Ø  A recent in vitro study had shown the efficacy of a new photosensitizer dye, indocyanine green (ICG), against Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, when activated at a wavelength of 810 nm by a diode laser. It has high absorption in the infrared spectrum, low toxicity, and rapid elimination.4

Ø  Methylene blue has a strong absorption band in the 550-700 nm region and has been extensively used for photooxidation of natural and synthetic molecules. Fontana et al, in 2009, demonstrated aPDT with 25 μg/mL methylene blue and red light resulted in 63% reduction of planktonic bacteria and 32% decrease in bacteria forming biofilms.5

Ø  The photokilling rate in antimicrobial photodynamic therapy is highly related to interaction of reactive oxygen species (ROS) produced, ability of photosensitizers (PS) in incorporating into microorganisms and light devices/microorganism type.6

Ø  While methylene blue and indocyanine green are present in the dental practice as PS there is an acute paucity of literature comparing their efficacy in terms of improvement of clinical parameters and suppression of periodontal pathogens. Therefore, the present study aims at comparative evaluation of antimicrobial effect of indocyanine green and methylene blue dye as photosensitizers for photodynamic therapy as an adjunct to scaling and root planing in patients with moderate periodontitis.