Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 2026 2 2026 08 25 233 237 Fateme Gharibpour Department of Orthodontics, School of Dentistry, Guilan University of Medical Sciences, Rasht, Iran. Paria Dehghanian Department of Orthodontics, Texas A&M University College of Dentistry, TX, USA. Mohsen Nosouhian Private Practice, Shahrekord, Iran. Nariman Nikparto Private Practice, Nastaran Dental Clinic, Tehran, Iran. Rashin Bahrami Department of Orthodontics, School of Dentistry, Iran University of Medical Sciences, Tehran, Iran. 2025 12 31 2026 07 12 Tooth transposition poses a significant challenge in dental clinics when it comes to treatment. The exact cause of tooth transposition remains a topic of debate and is still not fully understood. Approximately 20% of transpositions that occur in the upper arch involve the canine and lateral incisor. Although relatively uncommon, transpositions can also affect the upper central and lateral incisors. Among all transpositions, the mandibular lateral incisor-canine transposition is exceptionally rare, with a prevalence rate as low as 0.03%. Tooth transposition in the posterior side of the mandible is an uncommon occurrence. However, the present case report with complete transposition of the mandibular right second premolar erupted in the distal of the mandibular right first molar in a 12-year-old male patient with class II malocclusion is a rare case entity for clinical consideration. The current study proposed a factor or etiology, which is the correlation between the position of the tooth and inadequate growth of the mandible, as a potential explanation for complete transposition involving the mandibular second premolar. Further research and clinical studies are necessary to validate this etiology and gain a better understanding of the underlying mechanisms of tooth transposition.  Keywords: Mandibular premolar; Transposition; Mandibular deficiency; Malocclusion; Angle class II. https://jcr.tums.ac.ir/index.php/jcr/article/view/612 https://jcr.tums.ac.ir/index.php/jcr/article/download/612/502