A CBCT Study Of Hard Tissues In The Canine Area Of Adolescent Malocclusion With Different Skeletal Types

Objective:The study presented in this thesis aims to used of CBCT measure and analyze the thickness and height of alveolar bone in the canine area and bone defects in adolescent skeletal malocclusions with different skeletal surface types,and investigate the hard tissue and sagittal shape of the canine area in adolescents with skeletal malocclusion.The relationship between the angle of skeletal face ANB and the angle of vertical skeletal face FMA provides a theoretical basis and reference to some extent for the formulation of orthodontic plans and clinical treatment.Methods:A total of 105 cases(equivalently a total of 420 canine teeth)before orthodontic treatment eligible for inclusion were screened,including 42 males and 63 females,with ages ranging from 12 to 18 years old.According to the angle of the sagittal surface type ANB,is the cases were divided into skeletal type I,skeletal type Ⅱ,and skeletal type Ⅲ.According to the angle of the vertical bone surface type FMA,the cases were divided into low angle type,average angle type,and high angle type.The New Tom NNT viewer is used to reconstruct and analyze CBCT images,and measure the height of the alveolar crest on the labial and lingual sides of the upper and lower canines,the thickness of the alveolar crest on the labial and lingual sides,and the thickness of the alveolar bone on the labial and lingual sides of the root apex.Statistical analysis was performed using SPSS 21.0 statistical software,measurement data were compared between groups using one-way analysis of variance;pairwise comparison was performed using LSD-t test,and Pearson correlation coefficient was used for correlation analysis.the chi-square test was adopted for the enumeration data,with the significance level set to α=0.05.Results:1.The height of alveolar crest of different bone surface types:there is no difference in the height of the alveolar crest on the labial and lingual sides of the maxillary canine(P>0.05),which is weakly negatively correlated with the FMA angle(P<0.05).The height of the alveolar crest on the labial and lingual side of the mandibular canine is the lowest(P<0.05),which is positively correlated with the FMA angle(P<0.01).The height of the alveolar crest on the labial and lingual side of the mandibular canine is the lowest(P<0.05),which is negatively correlated with the FMA angle(P<0.01).2.Thickness of alveolar crest and labial alveolar bone thickness at the apex:the thickness of the alveolar crest on the labial and lingual side of the maxillary canine and the labial alveolar bone thickness at the apex have nothing to do with bone types(P>0.05).The thickness of the labial alveolar crest of the mandibular canine and the thickness of the labial alveolar bone at the apex are thickest in the low-angle type(P<0.05),which is negatively correlated with the FMA angle(P<0.01).The order of thickness of the lingual alveolar crest of the mandibular canine is bony typeⅢ<bone type Ⅱ(P<0.05),which is weakly positively correlated with ANB(P>0.01),and weakly negatively correlated with FMA(P<0.01).3.The thickness of the lingual alveolar bone at the apex:the sequence of the thickness of the lingual alveolar bone at the apex of maxillary canines of different bone types is:bony type III<bony type I<bony type Ⅱ(P<0.05),high angle<average angle and low angle(P ＜0.05),which are weakly positively correlated with ANB angle(P<0.05),and weakly negatively correlated with FMA angle(P<0.01).The thickness of the lingual alveolar bone at the apex of the mandibular canine is the bony type I<bony type Ⅱ(P<0.05),high angle type<average angle type and low angle type(P<0.05),which is weakly negatively correlated with FMA angle(P<0.01).4.Lip-tongue alveolar bone thickness at the apex:the order of thickness of the lip-tongue alveolar bone at the apex of the maxillary canine is high angle type<average angle type and low angle type(P<0.01),which is weakly negatively correlated with FMA angle(P<0.01).The ratio of the thickness of the alveolar bone on the labial and palatal sides of the maxillary canine area show that:skeletal type Ⅱ<skeletal type I and skeletal type III(P<0.05),average angle type,and low angle type<high angle type(P<0.05).The order of the thickness of the lip-tongue alveolar bone at the apex of the mandibular canine is skeletal type Ⅰ<skeletal type Ⅲ(P<0.01),and high angle type<average angle type<low angle type(P<0.05),and weakly negatively correlated with ANB angle(P<0.01),negatively correlated with the FMA angle(P<0.01).5.Bone defect detection rate:the detection rate of alveolar bone defect in the canine area is not different from the sagittal bone surface type(P>0.05).The detection rate of the high-angle type with the vertical bone surface type canine area and the simultaneous bone opening and dehiscence was higher than that of the average-angle type and the low-angle type(P<0.05).Conclusions:1.The height of the alveolar crest on the lip and tongue side of the mandibular canines decreases with the increase of the FMA angle,and the possibility of dehiscence increases.The thickness of the lingual alveolar crest of the mandibular canines increases with the increase of ANB angle,and the thickness of the labial and lingual alveolar crest decreases with the increase of FMA.2.The thickness of the lingual alveolar bone at the root apex of the maxillary canine increases with the increase of ANB angle,and decreases with the increase of FMA.The thickness of the alveolar bone at the root apex of the mandibular canine decreases with the increase of the ANB angle,and decreases with the increase of the FMA.The apex of skeletal class Ⅱ mandibular canines and skeletal class III mandibular canines are biased toward the labial side,and there is more space for the lingual side to move than the labial side.3.The detection rate of dehiscence and simultaneous dehiscence and fenestration in patients with high-angle type is higher than that of average-angle type and low-angle type.