Chulalongkorn University Dental Journal

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Objective To estimate the prevalence and distribution of impacted premolars in a group of New Zealand children aged 10 to 15 years and to report any associate findings. Materials and methods Panoramic radiographs of 1608 children aged 10 to 15 years were selected. All children had been registered as patients of the School of Dentistry, University of Otago, Dunedin, New Zealand since 1969. The radiographs were taken on the same panoramic machine and examined by one experienced radiologist for the presence and location of the impacted premolars and any associate pathological changes. Results One hundred and sixty nine individuals (10.5%) had 291 impacted premolar teeth. Among these teeth, the most frequently impacted premolar was the lower second premolar (59.1%), followed by the upper second premolar (26.1%), the lower first premolar (14%), and the upper first premolar (0.6%). Three-quarters of the impactions were in the mandible. The distribution of impactions were approximately equal on both sides except for first premolars, which were more common on the right side. Vertical impaction was the most frequent type of impaction (46%), followed by mesioangular (39%), distoangular (14%) and transverse (1%). Enamel hypoplasia affecting the crown of the impacted tooth was diagnosed in 3 children, and one child had an associated dentigerous cyst. Conclusion Panoramic radiographs showed a 10% prevalence of impacted premolars and few associated pathological changes in a group of New Zealand children. The frequency and type of impaction varied depending on the tooth number. This study demonstrated the importance of the panoramic radiograph in detecting various types of premolar impaction and associate findings.



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