[A statistic analysis on absence of third molar germs in orthodontic patients]

To examine the absence of the third molar germs in orthodontic patients and to evaluate the relationship between third molar germs and malocclusion.

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 statistic chi2 test.

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 either maxilla or mandible. The absent percentage of third molar germs in skeletal III subjects was higher than those in both skeletal class I and II subjects. The absent difference of third molar germs was in upper arches (P < 0.05), but not in lower arches (P > 0.05). There was no significant difference in absent percentage of third molar germs between skeletal class I and II subjects.

Male patients have higher absent frequencies of third molar germs than female ones. Skeletal class III patients have higher absence of third molar germs in upper jaws than skeletal class I and II patients.