Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 11 3 2014 06 15 319 27 Ali Peimani Assistant Professor, Department of Oral Surgery, Dental School of Rafsanjan University, Rafsanjan, Iran. Farimah Sardary Assistant Professor, Department of Oral Medicine, Dental School of Rafsanjan University, Rafsanjan, Iran. 2015 10 16 Temporomandibular disorders (TMD) are clinical conditions characterized by pain and sounds of the temporomandibular joint (TMJ). This study was designed to assess the effect of low-level laser therapy (LLLT) on healing of osteoarthritis in rats with TMD.Thirty-two male Wistar rats (250-200 g) were housed in standard plastic cages. After injection of Complete Freund's adjuvant into the TMJ, rats were randomly divided into two groups of 16 (case and control) and anesthetized; then osteoarthritis was induced via intraarticular injection of 50 µl of Complete Freund's adjuvant; into the bilateral TMJs. In the case group, LLLT was done transcutaneously for 10 minutes daily, starting the day after the confirmation of osteoarthritis. Exposure was performed for 10 minutes at the right side of the TMJ with 880 nm low-level laser with 100 mW power and a probe diameter of 0.8 mm. Control rats were not treated with laser.After three days of treatment the grade of cartilage defects, number of inflammatory cells, angiogenesis, number of cell layers and arthritis in rats in the case group were not significantly different compared with controls (P>0.05). After seven days, the grade of cartilage defects, number of inflammatory cells, number of cell layers, and arthritis in the case group improved compared to controls (P https://fid.tums.ac.ir/index.php/fid/article/view/450 https://fid.tums.ac.ir/index.php/fid/article/download/450/426