Photodynamic Therapy Effect on Colony Count of Porphyromonas Gingivalis (An In Vitro Study)

Periodontitis is a microbial related inflammatory and prevalent disease causing destruction of tooth supporting tissues. A lot of bacteria are involved in the etiology of periodontitis. Three methods, including surgery, antibiotic therapy, and laser are the most important treatment methods available at the clinician’s disposal.
In this study, the Porphyromonas gingivalis was cultured in vitro in 20 plates. Then, the plates were divided into 2 sections: the 1st group, the examined group, consists of 15 plates and the 2nd group, the control group, consists of 5 plates. Colonies of Porphyromonas gingivalis were counted using a light microscope. Then, the photosensitizing agent (Methylene Blue 1%) was added to test group plates. Furthermore, the examined plates were treated by 810nm, 0.9W laser for 5, 10, 15, and 30 seconds. Colonies were counted separately and recorded accordingly, then, before, and after treatment.
To compare before and after treatment, paired t-test, and for quantitative comparison of groups, (K2) square were used. The intervention group was treated and the laser was irradiated for 5, 10, 15, and 30 seconds. After 5 seconds, the colonies reduced significantly and after 15 seconds all Porphyromonas gingivalis were disappeared. In controls, which were not exposed to the laser beam, the colonies of Porphyromonas gingivalis almost remained without change.
This study showed that photodynamic therapy in the in vitro situation decreased the number of colonies of Porphyromonas gingivalis significantly after 10 seconds and eliminated them after 15 seconds.