Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 2 1 2005 03 15 33 35 JB Taheri M Baharvand AR Vahidi-Ghahrodi 2015 10 03 Fusion is a developmental anomaly defined as the union of two normally separated tooth buds or the partial splitting of one tooth bud into two buds. Depending on the stage of development, fusion may be either complete or incomplete. The significance of this particular case was that this fusion occurred in a posterior permanent mandibular tooth, while such a manifestation is more reported in maxillary anterior teeth; either in the primary (0.5%) or permanent (0.1%) dentition. The genetic basis for this anomaly is probably autosomal dominant with reduced penetrance. In addition, the essential findings for differential diagnosis include number of teeth, radiography and clinical features. https://fid.tums.ac.ir/index.php/fid/article/view/47 https://fid.tums.ac.ir/index.php/fid/article/download/47/47