Isfahan University of Medical SciencesDental Research Journal1735-33279320120821Prevalence and pattern of hypodontia in the permanent dentition of 3374 Iranian orthodontic patients10791079ENFariborzAminiVahidRakhshanDepartment of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran. vahid.rakhshan@gmail.comPardisBabaei20120821Background: Hypodontia is the most common dental anomaly and might cause clinicalcomplications. The aim of this study was to assess the prevalence and pattern of congenital missingin the permanent dentition dentition (excluding third molars), among Iranian orthodontic patients.Materials and Methods: In this descriptive cross-sectional study, all approved panoramicradiographs of 3374 orthodontic patients (aged 10 to 20 years old), who had visited the OrthodonticDepartments of all Tehran Dentistry Universities and 10 private clinics during the years 1999 to2009 were investigated, to establish the prevalence of hypodontia in the permanent dentition(excluding third molars). The data were analyzed using a chi-square test (α = 0.01).Results: Included were 2012 female and 1362 male patients. The prevalence of hypodontia was5.21% (5.86% in females, 4.25% in males). The difference between the genders in terms of missingteeth was not significant (P = 0.202). A total of 298 teeth were missing (166 in females, 132 inmales). The average of missing per individual was found to be 1.69 (1.40 missing for each girl, 2.32for each boy). There was no significant difference between the number of missing teeth in malesand females (P = 0.160). The most common missing teeth were maxillary lateral incisors (37.2%),mandibular second premolars (22.1%), and mandibular central incisors (10.7%). In both unilateraland bilateral hypodontia cases, the maxillary lateral had the highest prevalence of missing, followedby the mandibular second premolar. Missing was significantly more frequent (P = 0.001) in themaxilla (5.3%) compared to the mandible (3.5%).Conclusion: Out of every 20 Iranian orthodontic patients, one might have some missing permanentteeth, needing early attention. Hypodontia was more prevalent in females (though not significantly)and in the maxilla. Although more females were affected, the number of missing per individual wasgreater in males.Key Words: Hypodontia (congenital missing of teeth), permanent dentition, prevalence