Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 8 4 2022 06 11 178 186 Aryan Hesam Arefi Dental Research Center, Zahedan University of Medical Sciences, Zahedan. Iran. Seyed Morteza Samimi Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Reza Ghorbani Dentist, Gonabad, Iran. 2021 12 07 2022 04 22 Objectives: Impacted teeth fail to erupt fully into the oral cavity within the expected time due to interferences with the jaw bone, adjacent tooth, or even the gingivae. The third molar impaction frequency is related to space deficiency in dental arches. This study investigated different patterns of third molar impaction in various skeletal malocclusions in anteroposterior and vertical dimensions. Materials and Methods: In this study, 362 panoramic and lateral cephalograms of the patients with orthodontic treatment indications were verified and investigated. The malocclusion type was determined and diagnosed using lateral cephalogram tracing. Results: 39.2% of the patients were male, and 60.8% were female. The mean age of all the patients was 19.2 years; 35.6% of patients exhibited deep bite, and 32% had class II malocclusion. 44.5% of patients had two impacted third molars, and 23.5%, 20.7%, and 11.3% had four, one, and three impacted third molars, respectively. The frequencies of the mesio-angular pattern were 80.8% and 83.5% in the left and right quadrants of the mandible, respectively. The disto-angular pattern frequencies in the left and right quadrants of the maxilla were 91.1% and 93.3%, respectively. Conclusion: The current study revealed that the highest incidence of third molar impaction was in the deep bite and class II malocclusions. The most common pattern of impaction was mesio- angular and disto-angular in the mandible and maxilla, respectively. Statistical analysis showed no significant relationship between the numbers and patterns of third molar impaction and skeletal malocclusion types. . https://jcr.tums.ac.ir/index.php/jcr/article/view/398 https://jcr.tums.ac.ir/index.php/jcr/article/download/398/338