Alveolar Bone Morphology Of The Maxillary And Mandible Central Incisors In Skeletal Class Ⅲ Patients After Camouflaged Treatment: A CBCT Study

Objective:Cone beam computed tomography（CBCT）was performed before and at the end of treatment in patients with skeletal Class Ⅲ malocclusion who were treated with camouflaged treatment.To study the effect of camouflaged treatment on alveolar bone morphology of upper and lower central incisors and the movement of teeth,so as to provide reference for the safety evaluation of orthodontic disguised treatment of skeletal Class Ⅲ malocclusion.Methods:Twenty-nine patients with skeletal Class Ⅲ malocclusion who received orthodontic treatment in Hospital of Stomatology Hebei Medical University since 2016 were included.All patients were scanned with CBCT before treatment（T₀）and after treatment（T₁）,and the upper and lower central incisors were used as the measurement area with invivo5.1.3 software.The measurement items included:（1）The incidence of bone fenestration and bone cracking in the labial and lingual（palatal）alveolar bone.（2）the thickness of labial and lingual（palatal）side of alveolar bone（ULa,UP,LLa,LP）measurement:Four measuring lines（enamel cementum boundary,root apex and two equal points between two points）perpendicular to the tooth long axis were made to measure the thickness of alveolar bone at 1/3 of the root neck,1/3 of the apical and apical sites on the lingual（palatal）side.（3）thickness of alveolar bone on the lingual（palatal）side（d1,d2,d3,d4）:the distance from enamel cementum junction to the top of alveolar ridge on the lingual（palatal）side.（4）tooth length（UL,LL）and inclination angle of teeth（U1-SN）and（L1-MP）.SPSS 22.0 statistical software was used to analyze the measurement data.Results:1.The detection rate of labial bone cracking of upper central incisor was20.69%before treatment and 41.38%at the end of treatment.The detection rate of labial bone fenestration of lower central incisor was 13.79%before treatment and 41.38%at the end of treatment（P<0.05）.The detection rate of labial bone fenestration was 1.72%before treatment and 1.72%at the end of treatment.The detection rate of palatal bone fenestration was 1.72%before treatment and 6.90%at the end of treatment.The detection rate of palatal bone cracking of upper central incisor was 20.69%before treatment and 34.48%at the end of treatment.The detection rate of labial bone cracking of lower central incisor was 62.07%before treatment and 68.97%at the end of treatment;28%before treatment and 62.07%at the end of treatment.The detection rate of lingual bone fenestration of lower central incisors was20.69%before treatment and 34.48%at the end of treatment.2.The thickness of alveolar bone at 1/3 of labial root neck of upper central incisor was 1.23±0.94mm before treatment and 0.92±0.31mm at the end of treatment and the difference was statistically significant（P<0.05）.The thickness of alveolar bone at 1/3 of palatal apex was 4.05±0.42mm before treatment and 3.41±1.15mm at the end of treatment,and the difference was statistically significant（P<0.05）.The distance from apical point to palatal cortex was 7.08±1.28mm before treatment and the difference was statistically significant（P<0.05）.The thickness of alveolar bone at 1/3 of the labial root tip of upper central incisor was 1.49±0.27mm before treatment and 1.62±0.19mm at the end of treatment,the difference was not statistically significant.The thickness of alveolar bone at the labial root tip of upper central incisor was2.91±0.42mm before treatment and 3.37±0.58mm at the end of treatment,and the difference was not statistically significant.The thickness of alveolar bone at 1/3 of palatal root neck of maxillary central incisor was 2.39±0.68mm before treatment and 2.38±0.85mm at the end of treatment,and the difference was not statistically significant.The total thickness of alveolar bone at the apex of maxillary central incisor was 10.00±1.54mm before treatment and9.34±1.61mm at the end of treatment,and the difference was not statistically significant.The thickness of alveolar bone at 1/3 of lingual apex of lower central incisor was 2.46±0.94mm before treatment and 1.54±0.94mm at the end of treatment,the difference was statistically significant（P<0.05）.The distance between apical point and lingual bone cortex was 5.28±0.82mm before treatment and 4.30±0.66mm at the end of treatment,and the difference was statistically significant（P<0.05）.The total thickness of alveolar bone in apical area was 9.04±1.67mm before treatment,and the difference was statistically significant（P<0.05）.The thickness of alveolar bone at 1/3 of labial root neck of lower central incisor was 10.41±0.09mm before treatment and0.46±0.17mm at the end of treatment,and the difference was not statistically significant.The thickness of alveolar bone at 1/3 of labial root tip of lower central incisor was 0.92±0.44mm before treatment and 0.70±0.63mm at the end of treatment,and the difference was not statistically significant.The thickness of alveolar bone at labial apex of lower central incisor was3.76±1.47mm before treatment and 3.25±1.83mm at the end of treatment with no statistical significance.The thickness of alveolar bone at 1/3 of lingual root neck of lower central incisor was 0.94±0.77mm before treatment and0.70±0.39mm at the end of treatment with no statistical significance.3.The distance from enamel cementum junction to alveolar crest was1.83±0.58mm before treatment and 1.96±0.46mm at the end of treatment,and the difference was not statistically significant.The distance from palatal enamel cementum to alveolar crest was 2.00±0.60mm before treatment and2.02±0.54mm at the end of treatment,and the difference was not statistically significant.The distance between the labial enamel and the crest of the alveolar ridge of the lower middle incisors was 2.42±0.57mm before treatment,and2.81±0.45mm at the end of the treatment,and the difference was statistically significant（P<0.05）.the distance between the lower middle incisor lip enamel and the crest of the alveolar ridge was 2.15±0.51mm,and 2.66±0.44mm before the treatment of the fascicle,and the difference was statistically significant（P<0.05）.4.The length of upper central incisor（UL）was 21.26±1.24mm before treatment and 20.62±1.12mm at the end of treatment,the difference was not statistically significant;the length of lower central incisor（LL）was20.15±0.74mm before treatment and 19.35±0.89mm at the end of treatment,the difference was statistically significant（P<0.05）.The upper central incisor angle（U1-SN）was 109.45±2.66°before treatment and 106.09±2.21°at the end of treatment（P<0.05）,the lower central incisor angle（L1-MP）was 86.25±4.46°before treatment and 82.25±3.88°at the end of treatment（P<0.05）.Conclusions:1.In mild to moderate skeletal Class Ⅲ patients,the compensatory labial movement of the upper central incisor and the compensatory lingual movement of the lower central incisor were observed after camouflaged treatment.The lingual alveolar bone in the apical area of the mandibular central incisor became thinner which made the alveolar bone in the apical area thinner,the attachment height of the mandibular alveolar bone tended to decrease.2.In mild to moderate skeletal Class Ⅲ patients,the incidence of labial bone cracking of upper central incisors increased,and the incidence of labial bone fenestration of lower incisors increased.Bone resorption was the main biological remodeling,and root resorption occurred during the movement of mandibular central incisors.3.Before taking camouflaged orthodontic treatment for mild to moderate skeletal Class Ⅲ patients,we should pay attention to the thickness and height of the alveolar bone in the upper and lower anterior teeth,especially the labial lingual（palatal）side of the lower anterior teeth,and pay attention to the safe movement range of the upper and lower anterior teeth,and choose the appropriate tooth movement speed and way in the orthodontic process,and pay close attention to the morphological changes of the alveolar bone,so as to avoid the periodontal risks such as fenestration,bone cracking,alveolar bone thinning and root resorption.