Investigation Epidemiology Of Hypodontia In800Orthodontic Patients And Correlation With Dental Anomalies

OBJECTIVEThe purpose of this study was to evaluate the prevalence and distributionof hypodontia in the permanent dentition，including the third molars，in asample of800Dalian orthodontic patients;and the prevalence ofsupernumerary teeth、peg-shaped teeth（or microdontia）、dilaceration andshort or blunt roots in a sample of800DaLian orthodintic patients withhypodontia(including the third molar),and the correlation with hypodontia.METHODSBased on pretreatment diagnostic records，the cases of800orthodonticpatients（260males，540females）between9to40Yrs in Stomatologicalhospital of Dalian from July2008to June2011were examined.800orthodontic patients between the age of9and40Yrs were examined to findout the cases of hypodontia,in which the prevalence of supernumerary teeth、peg-shaped teeth(or microdontia)、dilaceration、short or blunt roots wereassessed.Investigate the correlation between each dental anomaly andhypodontia using Pearson contingency coefficient.RESULTSThe prevalence of hypodontia was36.13%（including the third molar）and12.5%（excluding the third molar）. No significant statistical gender differencewas observed. The prevalence of mild hypodontia patients was87%and themoderate hypodontia patients was10%,the serious hypodontia patients was3%.the most frequently missing tooth was different according to the severity of hypodontia. The most frequently missing tooth was anterior tooth in mildhypodontic and was posterior in moderate or severe hypodontic.Theprevalence in mandibular was higher than maxillary in mild hypodontic,butthere was no difference in moderate or sevece hypodontic. There was nodifference between the prevalence of the left and right.when the number ofcongenital missing teeth is the same as two or beyond,symmetrical hypodontiawas predominant，and the most frequently missing tooth was the mandibularsecond premolar. In the cases of hypodontia,the prevalence of supernumeraryteeth was3.5%,the prevalence of peg-shaped teeth(or microdontia) was14.5%,the prevalence of dilaceration was3.5%,the prevalence of short or bluntroots was3.0%.Statistically significant correlations were found betweenpeg-shaped teeth(or microdontia) or short or blunt roots and hypodontia,Pearson contingency coefficient are0.169and0.097.CONCLUSIONExcluding the third molar，The most frequently missing tooth was themandibular lateral incisor， with the increasing of the number of absenced，themost frequently missing tooth became the mandibular second premolar. Aprevalence of peg-shaped teeth(or microdontia)、 supernumerary teeth、dilaceration and short or blunt roots was14.5%、3.5%、3.5%and3.0%in thecases of hypodontia.There were the correlations between the incidence ofpeg-shaped teeth(or microdontia) or short or blunt roots and hypodontia.