JKAU: Med. Sci., Vol. 18 No. 4, pp: 83-90 (2011 A.D. / 1432 A.H.) DOI: 10.4197/Med. 18-4.7 ________________________________ Correspondence & reprint request to: Dr. Laila A. Bahammam P.O. Box 35168, Jeddah 21488, Saudi Arabia Accepted for publication: 24 July 2011. Received: 08 May 2011. 83 The Incidence of Radix Entomolaris in Mandibular First Permanent Molars in a Saudi Arabian Sub-Population Laila A. Bahammam, BDS, MSc and Hammam A. Bahammam, BDS Department of Conservative Dental Science, Division of Endodontic and Intern Faculty of Dentistry, King Abdulaziz University Jeddah, Saudi Arabia lbahammam@yahoo.com Abstract. The aim of this study was to investigate the incidence of radix entomolaris in mandibular first permanent molars in Saudi Arabian sub- population. A total of 280 extracted mandibular first permanent molar were included in the study. The teeth were examined visually and the number of roots was recorded. The results showed that the majority of cases had two roots 93.9% (263 teeth), whereas the remaining 6.07% (17 teeth) had three roots. It is apparent from the previously reported studies and the findings of this study, that a higher frequency of occurrence of radix entomolaris in mandibular first molars in Saudi Arabian population than in other populations in west Asia. In addition to a higher frequency of occurrence in the East Asian population than in the West. Keywords: Anatomical variations, Endodontic treatment, Mandibular first molar, Radix entomolaris. Introduction The main objective of root canal treatment is the thorough chemomechanical cleansing of the entire root canal system, and its complete obturation with an inert filling material and a coronal filling preventing ingress of microorganisms. One of the main reasons for