J Invest Clin Dent. 2017;e12295. wileyonlinelibrary.com/journal/jicd | 1 of 8 https://doi.org/10.1111/jicd.12295 © 2017 John Wiley & Sons Australia, Ltd Received: 25 April 2017 | Accepted: 8 July 2017 DOI: 10.1111/jicd.12295 ORIGINAL ARTICLE Oral and Maxillofacial Surgery Dental extractions for preradiation dental clearance and incidence of osteoradionecrosis in patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy Yoong L. See Toh 1 | Yoke L. Soong 2 | Yi X. Chim 1 | Li T. Tan 1 | Weng K. Lye 3 | Khim H. Teoh 1 1 Department of Restorative Dentistry, National Dental Centre Singapore, Singapore, Singapore 2 Department of Radiation Oncology, National Cancer Centre Singapore, Singapore, Singapore 3 Centre for Quantitative Medicine, Duke-NUS Medical School, Singapore, Singapore Correspondence Dr Yoong L. See Toh, Department of Restorative Dentistry, National Dental Centre Singapore, Singapore. Email: see.toh.yoong.liang@singhealth.com.sg Abstract Aim: The aims of the present retrospective study were to evaluate the outcomes of dental extractions in nasopharyngeal carcinoma patients who had undergone dental clearance pre- and post-radiotherapy (RT) with intensity-modulated RT, and to report on the incidence and timing of osteoradionecrosis (ORN) in these patients. Methods: A total of 231 patients were seen pre-, mid-, and postradiation therapy. Information on patient demographics, smoking history, staging, treatment modalities, dental extraction indications, and number and site of dental extractions was gathered. Wilcoxon two-sample tests and Fisher’s exact test were used to test the association between groups for patient variables. Results: The mean number of teeth removed was 4.1 teeth per patient. A total of 334 (35.2%) teeth were removed for periodontal reasons, 322 (34.03%) were removed prophylactically, and the remaining teeth were removed because of deep caries, re- tained roots, partial impaction, endodontic lesions, and prosthodontic reasons. Patients had an average of 19.6 teeth remaining after dental clearance, and only 97 (42%) required prosthetic intervention. The statistical analysis showed that there was no correlation between dental extractions pre- or post-RT and the development of ORN. Conclusions: No specific parameter was directly associated with dental extractions, although smoking and increased number of teeth removed preradiation seemed to be prevalent in patients who developed ORN. KEYWORDS dental clearance, intensity-modulated radiotherapy, nasopharyngeal carcinoma, osteoradionecrosis, tooth extraction 1 | INTRODUCTION Nasopharyngeal carcinoma (NPC) is an epithelial cancer of the naso- pharynx, most commonly originating from the fossa of Rosenmüller, an anatomical depression posterior to the torus tubarius of the eustachian tube. 1 This neoplasm exhibits varying degrees of differenti- ation, but in the endemic population (southern China, south-east Asia, and northern Africa), undifferentiated carcinoma is the most common. In Singapore, NPC is the eight most common cancer in males, with an age-standardized incidence of 8.1/100 000/year. 2