Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 8 1 2021 07 07 11 15 Gholamreza Shirani Department of Oral and Maxillofacial Surgery, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Arghavan Tonkaboni Department of Oral and Maxillofacial Surgery, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran; Grupo De Investigacion En Patologia Oral Medico Quirurgica, Universidade de Santiago De Compostela, Spain. Mina Mazani School of Dentistry, International Campus, Tehran University of Medical Sciences, Tehran, Iran. Babak Mirzashahi Department of Orthopedic, Imam Khomeini Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Abel Garcia Garcia Department of Maxillofacial Surgery, University of Santiago De Compostela, A coruna, Spain. Mohammad Javad Kharazifard School of Dentistry, International Campus, Tehran University of Medical Sciences, Tehran, Iran. 2021 03 27 2021 04 20 Background: Medication related osteonecrosis of the jaw (MRONJ) is a chronic condition of the oral cavity resulting in mucosal ulceration and exposure of underlying necrotic bone, and the ensuing secondary complications. The aim of this study was to evaluate the relationship between vitamin D deficiency and osteonecrosis of the jaw related to bisphosphonates. Materials and Methods: This was a case-control study. The samples were 20 patients taking bisphosphonates, that 10 of them were with MRONJ and 10 were non-MRONJ. Clinical examination of patients was performed to diagnose jaw osteonecrosis. Demographic data of the patients were recorded including age, sex, type of drug, duration and cause of drug intake, and measurement of serum vitamin D levels. Data were analyzed using SPSS software. Results: In the patients without MRONJ, the mean age was 60.60 (±14.975) years, and in the patients with MRONJ, the mean age was 68.30 (69.92) years. As a whole, of the 16 female patients in this study, 10 cases (62.5%) were non- MRONJ and 6 cases (37.5%) were suffered by MRONJ. All of the male patients presented with MRONJ. In control group mean of vitamin D was 63.990 ng/ ml (±29.796) and in case group mean of vitamin D was 29.510 ng/ml (±23.723). The serum level of vitamin D (25-OHD) was significantly higher in control group than in the case group (p=0.010). Conclusion: According to our result, there were statistically significant relationship between age, sex, type of drug, vitamin D level, and MRONJ (p>0.05). Key words: MRONJ; Vitamin D; Bisphosphonates; Osteonecrosis of the jaws. https://jcr.tums.ac.ir/index.php/jcr/article/view/368 https://jcr.tums.ac.ir/index.php/jcr/article/download/368/316