Distribution of Congenitally Missing Teeth (Hypodontia) and Its Prevalence in Orthodontic Patients. Study at Princess Basma Teaching Hospital
Dr. Ali Abdul Kareem Abu Ain

Abstract
Study Background and its purpose: congenitally missing teeth (Hypodontia) is considered one of the frequently observed phenomena in the orthodontic clinic. Therefore, this study aimed to determine the prevalence of congenitally missing teeth and its relation to gender in a sample of orthodontics patients at the Princess Basma Teaching Hospital in Irbid from 08/2017 to 08/2018. Study Sample and its Methodology: The study sample consisted of 2212 patients who visited the orthodontic clinic at the Princess Basma Teaching Hospital in Irbid, aged 9-27 years. The data of the study were collected through clinical and radiological examination of the patients, where the lost permanent teeth were counted. Pearson's chi-squared test (χ2) was used at 5% significance level to investigate the significance of differences between males and females. Results: The number of lost permanent teeth was 810 in 196 patients, which is 8.86% of the individuals of the population of the study. The study showed that (except the third molars), the maxillary lateral incisor is the most lost by 36%. Then, the mandibular second premolars with 28% followed the maxillary second premolars and the mandibular molars by 9% . The first premolars were lost by 6% then the mandibular second molars by 5%, while the canines, the maxillary second molars and maxillary central incisor were rarely absent. There was no observation about the absence of the maxillary and mandibular first molars. It was noticed that 88% of the patients have lost more than one tooth. The arithmetic average of lost teeth in the males (except the third molars) equal 2.16 teeth while it was equal 2.36 for the females which indicates that there is no significant difference according to gender. Recommendations: the percentage of congenitally missing teeth was high especially the mandibular second premolars and the maxillary lateral incisors. The study recommended making panoramic images for the patients before treatment.

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