| Background:The Class Ⅱ malocclusion can be divided into two subcategories: Class Ⅱclassification 1(upper incisor lip inclination)and Class Ⅱ classification 2(upper incisor tongue inclination).In the treatment of two malocclusion malformations,the torque control of the anterior teeth and the vertical control of the anterior teeth are both difficult and key.Existing studies have shown that mini-implants implanted in the anterior dental region can not only assist the compression of the anterior teeth and the opening of the bite,but also assist the control of the torque of the anterior teeth in the process of the anterior adduction,and the good stability of the mini-implants is the premise to achieve these correction goals.At present,mini-implants are mainly implanted between anterior teeth roots,that is,between bilateral central incisor roots,between bilateral lateral incisor roots and central incisor roots,and between bilateral lateral incisor roots and cusp roots.Factors affecting the stability of mini-implants in the above areas were mainly bone anatomical structure at the implant location,including the width between the roots of the teeth,the thickness of the lip and lingual bone cortex,and the thickness of the lip and lingual bone.Studies have shown that there are differences in the anatomic morphology of labial alveolar bone in the anterior dental region of patients with Class Ⅱ malocclusion.However,there are no reports on the anatomic morphology of alveolar bone in the anterior dental region of patients with Class Ⅱ malocclusion.Objectives of the study:In this study,CBCT measurement was used to analyze the anatomical structure of alveolar bone at the implant site of anterior dental orthodontic mini-implant in patients with Class Ⅱ malocclusion and individual patients with normal occlusion,and to explore the factors affecting the anatomical structure of alveolar bone at the implant site of anterior dental orthodontic mini-implant,so as to provide reference for the selection of the implant site and the size and model of the mini-implant in clinical anterior dental area.Research methods:Sixty-two adult skeletal Class I patients were divided into three groups: individual normal jaw group(group A,n = 21),Class Ⅱ division 1 group(group B,n = 21)and Class Ⅱ division 2 group(group C,n = 20).CBCT was taken and DICOM data were imported into the Smart V2 image processing system for three-dimensional image reconstruction.The distances between the roots of bilateral maxillary central incisors,central incisors and lateral incisors,lateral incisors and canine roots were measured14 mm,17mm,and 17 mm above the reference plane.The thickness of labial and lingual cortical bone,the thickness of labial and lingual bone and the width between the roots at the height of 20 mm were statistically analyzed by SPSS 23.0 software.One-way ANOVA was used for inter-group and intra-group comparison.Pearson test was used for correlation analysis.P < 0.05 meant that the difference was statistically significant.Findings:1.The thickness of labial cortex and labiolingual bone at the same measurement site in the anterior dental region were statistically different among patients with different malocclusion(P<0.05),which showed that individual normal occlusion group(group A)≥ Angle Class Ⅱ Group 1(group B)> Angle Class Ⅱ group C.2.There was no significant difference in the thickness of labial cortex at the height of 20 mm in some normal occlusion group(Group A)and the thickness of labial cortex,apical width at the height of 17 mm and apical width at the height of 20 mm in group B.In other measurement sites,There were statistically significant differences between the measured values of different dental positions in the anterior dental region of the same malocclusion deformity(P<0.05)3.In terms of bone thickness,the thickness of labiolingual bone at all measurement sites was greater than 7mm;In terms of the cortical thickness of lip-lingual bone,the cortical thickness of the labial bone was greater than 1mm in the 14 mm height between the incisor root and the central incisor root and the lateral incisor root in the patients with Class Ⅱ and Class 2,except that the cortical thickness was less than 1mm in the other areas.In terms of interroot width,except for the 14,17 mm height between the central incisor and lateral incisor in some normal occlusion patients and the 14 mm height between the incisor and lateral incisor in Class Ⅱ group 1,the interroot width in other areas could reach 3mm.4.At the height of 14,17 and 20 mm,the thickness of labiolingual bone and the thickness of labiolingual bone were positively correlated with U1-NA/(mm)and U1-NA/(°),and negatively correlated with the Angle of ANB.The distance between the teeth roots was negatively correlated with U1-NA/(mm)and U1-NA/(°).Conclusions:1.There are significant differences in the anatomical morphology of the alveolar bone at the implant site of the anterior dental region of patients with different malocclusion,and there are also significant differences in the anatomical morphology of the implant site of the anterior dental region between different dental positions of the same malocclusion.It is recommended to use CBCT to fully evaluate the bone condition of the implant site before mini-implant implantation.To select the best implantation site and the most appropriate mini-implant size.2.Mini-implants with length of 7mm can be selected for each implant site in the anterior tooth area of Class Ⅱ and individual normal occlusion patients.3.In patients with Class Ⅱ and Class 2,the mini-implants should be implanted at a certain Angle in the 14 mm height area between the bilateral central incisor teeth and between the central incisor teeth and the lateral incisor teeth,or longer mini-implants should be selected to achieve bilateral cortical bone implantation.These two methods can increase the thickness of the cortical bone in the implant area and thus improve the stability of the mini-implants after implantation.4.The 14,17 mm height between the central and lateral incisors of individual normal maxillary patients and the 14 mm height between the incisors and lateral incisors of Class Ⅱ group 1 were smaller,so it is recommended to avoid these implant sites clinically.In order to ensure sufficient inter root width of the tooth to prevent damage to bilateral anatomical structures during and after implantation of mini-implants,and even cause loosening and loss of mini-implants. |
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