CBCT Measurement Of Mandibular Shape And Impacted Mandibular Wisdom Teeth

Objective:To investigate the relationship between mandibular shape and mandibular wisdom tooth impaction using CBCT,analyze the influence of various measurement indicators of mandibular shape on whether and where impacted mandibular wisdom teeth were,and explore the independent factors affecting the impacted mandibular wisdom teeth.Methods:According to the inclusion criteria and exclusion criteria,according to the results of CBCT imaging examination,80 patients(112)aged between 20 and 35 years with mandibular wisdom teeth were included in the study and divided into the eruption group(56)and the impaction group(56);the impaction group was divided into three groups:class I(15),class II(24),and class III(17).CBCT measurement indicators include:mandibular ramus inclination,length,width,upper end curvature,relative height,the maximum distance of mandibular volume,the length of the lower edge of the mandibular body,the size of the mandibular angle and the height of the lower posterior alveolar 9indicators.The data were imported into SPSS 25.0 for statistical analysis and expressed as mean ± standard deviation((?)±s).Independent t test was used for comparison between the two groups.When P <0.05 was used,the difference was statistically significant.Logistic regression analysis was used for measurement indicators with statistical significance.One-way analysis of variance was used for comparison between multiple groups.LSD method was used for comparison.When P <0.05 was used,the difference was statistically significant.Results:1.the mandibular ramus slope of the impacted group(79.98 ± 4.18)° and the size of the mandibular angle(118.26 ± 7.31)° were greater than those of the erupted group(78.44± 3.86)° and(115.33 ± 7.56)°,and the difference was not statistically significant(P >0.05);the mandibular ramus length of the impacted group(40.27 ± 4.67)mm,the mandibular ramus width(23.67 ± 2.94)mm,and the maximum distance of the mandibular volume(73.83 ± 5.89)mm were less than those of the erupted group(41.78 ± 4.41)mm,(24.81 ± 2.66)mm,and(77.59 ± 6.36)mm,and the difference was not statistically significant(P > 0.05).2.The curvature of the upper end of the mandibular ramus(104.32±10.95)mm and the relative height ratio of the mandibular ramus(0.55±0.08)in the impacted group were greater than those in the eruption group(100.16±7.51)mm and(0.54±0.06),and the differences were statistically significant(P<0.05).3.The length of the lower edge of the mandibular body in the impacted group(48.49±3.85)mm and the height of the inferior posterior alveolar(21.41±2.40)mm were smaller than those in the eruption group(51.51±5.49)mm and(23.90±3.34)mm,and the differences were statistically significant(P<0.05),and these two indicators were independent protective factors for impacted mandibular wisdom teeth.4.The analysis of the subgroups of the impacted group showed that the maximum distance of mandibular volume between Class I,II,and III impactions was(78.13 ± 4.10)mm,(73.98 ± 6.01)mm,and(70.47 ± 4.23)mm,respectively,and there were significant differences between the two groups(P < 0.05);the length of the lower edge of the mandibular body between Class I,II,and III impactions was(50.74 ± 4.79)mm,(48.20 ±3.06)mm,and(46.91 ± 3.14)mm,respectively,and there were significant differences in the length of the lower edge of the mandibular body between Class I impactions and Class II and III impactions(P<0.05),and there were no significant differences in the length of the lower edge of the mandibular body between Class II and III impactions(P > 0.05).Conclusion:1.The curvature of the upper end of the mandibular ramus,the relative height of the mandibular ramus,the shorter the length of the lower edge of the mandibular body,and the lower the height of the lower posterior alveolus of the mandible are more likely to cause mandibular wisdom tooth impaction.2.The length of the lower edge of the mandibular body and the maximum distance of the mandibular volume affect the position of the mandibular wisdom tooth;the maximum distance of the mandibular volume and the longer the length of the lower edge of the mandibular body,the more likely it is to have Class I impaction.3.The length of the lower edge of the mandibular body and the height of the lower posterior alveolus can be used as indicators to predict whether the mandibular wisdom tooth can erupt;the longer the length of the lower edge of the mandibular body and the height of the lower posterior alveolus,the greater the possibility of mandibular wisdom tooth eruption.