Photodynamic therapy (PDT) is widely used in medicine to treat tumours, pre-malignant lesions, macular degeneration and psoriasis, and in dentistry it is applied to periodontal pockets, herpes simplex and other microbial lesions. This therapy consists of combining a low-intensity light source with a dye. Bacteria, fungi, yeasts and viruses can also be eliminated by visible light after treatment with an appropriate photosensitiser. In this study, the effect of PDT on the dental alveoli of lower third molars immediately after extraction was verified "in vivo", showing a drastic reduction in the amount of growth of microorganisms, a statistically significant reduction in pain and oedema, and a better scar appearance after seven days.