The Relationship Between The Absence Of The Third Molar Germs And Vertical Skeletal Type

Objective:This study was designed to survey the situation of clinical three vertical facial skeletal type and the situation of the absence of the third molar germs, in order to analyse whether relevant between them. Discuss the absence of the third molar germs of 300 cases orthodontics patients, and analyse the relationship between third molar germs and vertical skeletal type. Methods:The subjects comprised 300 patients from the orthodontic clinic of the Stomatological Affiliated Hospital of Luzhou Medical College from 2006 to 2010 whose ages were 14-18. The assessments of the third molar germs were made from panoramic radiographs, and the assessments of SN-MP,FH-MP angles were made from lateral cephalograms. Then ascertain the vertical facial skeletal type. Statistical three vertical facial skeletal type patients'the absence of M3 in four quadrants. In number and tooth germ respectively lack of number of statistical M3. Compare the lack of left right side M3, jaw M3 that loss, the lack of three vertical facial skeletal type M3. All the data were analyzed by statistic X2 test,0.05 meaningful boundaries. Results:In 300 patients, there are high angle 123 cases(female 77 cases, male 46 cases), average angle 126 cases (65 male,female 61 cases), low angle 51 cases (female 25 cases, male 26 cases).The percentage of subjects with one or more third molar germs missing was 24.33%; and the numeral percentage of third molar germs missing was 12.5%. There are 36 patients missing M3 in 131 Male, and there are 36 patients missing M3 in 169 female. There was no significant difference between the absent frequencies of third molar germs on left and right sides in either maxilla or mandible, nor in male and female(p>0.05). There was no significant difference between average angle patients and low angle patients either maxilla or mandible(p>0.05). The absent percentage of third molar germs in high angle patients are lower than average angle patients and low angle patients in maxilla(p<0.01), but no difference in mandible. Conclusion:The percentage of orthodontic patients with one or more third molar germs missing is about 25%, and there are 11 persons missing 4M3,about 3.67% in all patients. Maybe there are some relationship between the absence of third molar germs and vertical skeletal type, the absent percentage of third molar germs in high angle patients are lower than average angle patients and low angle patients in maxilla, about lower 5%.