关键词: 第三磨牙牙胚, 正畸, 统计分析

Abstract:

Objective　To examine the absence of the third molar germs in orthodontic patients and to evaluate the relationship between third molar germs and malocclusion.Methods　The subjects comprised 234 patients (male 92, female 142) from the orthodontic clinic whose ages were 14-18 .The assessments of the third molar germs were made from panoramic radiographs, and the assessments of ANB angle were made from lateral cephalograms. All the data were analyzed by statisticχ2test.Results　The percentage of male who missed one or more third molar gems (37.0%) was higher than that of female (24.6%). There was no significant difference between the absent frequencies of third molar germs on left and right sides in eithermaxilla ormandible. The absent percentage of third molar germs in skeletalⅢsubjectswas higherthan those in both skeletal classⅠandⅡsubjects. The absent difference of third molargermswas in upper arches (P<0.05), but not in lower arches (P>0.05). Therewas no signif- icant difference in absent percentage of third molar germs between skeletal classⅠandⅡsubjects.Conclusion　Male patients have higher absent frequencies of third molargerms than female ones. Skeletal classⅢpatients have higher absence of third molar germs in upper jaws than skeletal classⅠandⅡpatients.

Key words: third molar germ, orthodontics, statistic analysis