Janani M et al. Strange Anatomy of Maxillary First Molars. 123 Journal of Advanced Medical and Dental Sciences Research |Vol. 3|Issue 2| April - June 2015 STRANGE ANATOMY OF MAXILLARY FIRST MOLARS: AN ENDODONTIC CHALLENGE: REPORT OF THREE CASES Maryam Janani 1 , Ahmad Nouroloyouni 2 , Amirala Aghbali 3 , Bita Talebzadeh 4 , Vahide Asqary 5 , Sarah Nuroloyuni 6 1 Assistant professor of Endodontics, 2 Postgraduate student of Endodontics, 3 Associate professor of oral and Maxillofacial Pathology, 4 Postgraduate student of Endodontics, 5 Postgraduate student of Endodontics, 6 Assistant professor of pediatric dentistry, Faculty of Dentistry, Ardabil University of Medical Sciences, Ardabil, Iran. Corresponding Author: Ahmad Nouroloyouni, Golgasht Street, 5166614713, Tabriz, Iran, E-mail: a.noorolouni@gmail.com This article may be cited as: Janani M, Nouroloyouni A, Aghbali A, Talebzadeh B, Asqary V, Nuroloyuni S. Strange Anatomy of maxillary first Molars: An Endodontic Challenge: Report of three Cases. J Adv Med Dent Scie Res 2015;3(2):123-128. NTRODUCTION The main objectives of root canal therapy are thorough cleaning and shaping of all the canals and their obturation with an inert obturation material; therefore, successful root canal therapy requires a thorough knowledge on the root and root canal morphology and the possible variations. Maxillary first molars have the most complicated roots and canal morphologies of the maxillary dentition. 1,2 Based on a literature review, the most common form of maxillary first molar has three roots and four root canals. 2 Previous investigations have shown that maxillary first molars might have one to six root canals, 3-7 and cases with C-shaped canal configuration have also been reported. 8 One of the rarest anatomical variations in these teeth is taurodontism which was first described and reported by Gorjanovic-Kramberger in 1908. In 1913 Sir Arthur Keith proposed the term taurodontism for the “bull-like” configuration of teeth. 9 The characteristic features include an enlarged pulp chamber, apical displacement of the pulpal floor and no anatomical constriction at the level of the cementoenamel junction (CEJ). 10 The etiology of taurodontism is unclear. The most accepted cause is the failure of Hertwig’s epithelial sheath diaphragm to invaginate at the proper horizontal level. 11 Taurodontism has been reported to be associated with several developmental syndromes and anomalies. 11 Based on the severity and furcal displacement, taurodontism has been classified as follows: In hypotaurodontism, considered the mildest aberrant form, only the pulp chamber is enlarged; in mesotaurodontism, regarded as a moderate form, the roots are divided only at the middle third; and in I Case Report ABSTRACT: Background: Knowledge on the root canal system morphology of maxillary molars is an essential prerequisite for the success of root canal therapy. The aim of this article is to present endodontic management of three maxillary first molars with unusual root canal system morphologies. The most common form of maxillary first molar has three roots and four canals, but variations are always present. Methods: This case report presents one case of single unilateral mesotaurodont maxillary first molar in a healthy person, which is reported for the first time. The second case is a maxillary first molar with two canals in a single root as one of the rarest variations of maxillary first molars, and a maxillary first molar is presented with two roots and two canals. Results: This article extends the range of known possible anatomical variations to include teeth with fewer roots and canals. Conclusion: Clinicians must have proper knowledge on root canal morphology and the possible variations. Keywords: Anatomic variation, case report, maxillary first molar, root canal treatment.