Prevalence and pattern of hypodontia in the permanent dentition of 3374 Iranian orthodontic patients

Abstract

Background: Hypodontia is the most common dental anomaly and might cause clinical
complications. The aim of this study was to assess the prevalence and pattern of congenital missing
in the permanent dentition dentition (excluding third molars), among Iranian orthodontic patients.
Materials and Methods: In this descriptive cross-sectional study, all approved panoramic
radiographs of 3374 orthodontic patients (aged 10 to 20 years old), who had visited the Orthodontic
Departments of all Tehran Dentistry Universities and 10 private clinics during the years 1999 to
2009 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 was
5.21% (5.86% in females, 4.25% in males). The difference between the genders in terms of missing
teeth was not significant (P = 0.202). A total of 298 teeth were missing (166 in females, 132 in
males). The average of missing per individual was found to be 1.69 (1.40 missing for each girl, 2.32
for each boy). There was no significant difference between the number of missing teeth in males
and 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 unilateral
and bilateral hypodontia cases, the maxillary lateral had the highest prevalence of missing, followed
by the mandibular second premolar. Missing was significantly more frequent (P = 0.001) in the
maxilla (5.3%) compared to the mandible (3.5%).
Conclusion: Out of every 20 Iranian orthodontic patients, one might have some missing permanent
teeth, 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 was
greater in males.
Key Words: Hypodontia (congenital missing of teeth), permanent dentition, prevalence