Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 11 3 2014 06 15 355 60 Zahra Bahrololoomi Associate Professor, Department of Pediatric Dental School, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Roya Ghafourifard Assistant Professor, Department of Pediatric Dental School, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Ali Asghar Soleimani Assistant Professor, Department of Pediatric Dental School, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 2015 10 16 Single rooted primary mandibular first molar is a rare developmental anomaly. Literatures reveal that failure of invagination of Hertwig's epithelial root sheath leads to this unusual root form. Thorough knowledge of root canal morphology and anatomical variations of primary teeth can help a pediatric dentist in successful root canal treatment. Hereby, we describe two cases of primary mandibular first molars with an unusual morphology as a single root called pyramidal molar. https://fid.tums.ac.ir/index.php/fid/article/view/442 https://fid.tums.ac.ir/index.php/fid/article/download/442/418