A CBCT Analysis Of The Density Of Alveolar Bone With Class Ⅲ Skeletal Adults In Different Vertical Facial Types

Objective:The purpose of this study was to quantitatively evaluate the cortical density of maxillary and mandibular alveolar bone in adult patients with different vertical facial types using a cone-beam computed tomography(CBCT)image,in order to provide reference for the selection of the mini-implant placement sites in orthodontic treatment.Methods:According to the measured values of ANB and mandibular plane angle FMA(FH-MP),60 CBCT images of adult skeletal class III patients(20-35 years old)were selected and divided into three groups:low angle group(20 cases)and mean angle group(20 cases)and high angle group(20 cases).The cortical density(unit:Hounsfield)at maxillary and mandibular interdental sites from the distal aspect of the canine to the mesial aspect of the second molar were measured on the images,and the results were statistically analyzed.Results:There was no significant difference in bone cortical density between the left and right jaws of the patients in different measurement areas(P>0.05).The difference of alveolar septal cortical density in skeletal class III patients with different vertical facial types was statistically significant in the 4-5,5-6 regions of the upper jaw(including the buccal and palatal sides)and the 4-5,5-6 regions of the mandibular buccal side(P<0.05),high angle group<low angle group;the difference in the cortical density between the buccal and palatal sides of the skeletal class III patients was statistically significant,and the buccal side was higher than the palatal side.For the skeletal class III patients with different vertical bone types,the difference in alveolar space between 6-7 of the male and female maxillary palatal sides of the lower angle group was statistically significant(P<0.05),and the female was higher than the male;In the mean angle group,there was a statistically significant difference in the density of alveolar septal cortex between 4-5 of the maxillary palatal side,6-7 of the maxillary palatal side,and 6-7 of the mandibular buccal side(P<0.05).Female were higher than male;In the high angle group,the difference in bone cortical density in all measurement areas of the maxillary palatal side was statistically significant(P<0.05),and women were higher than men.Conclusions:The cortical density of the maxillary and mandibular alveolar bone in adult skeletal class III patients is related to the vertical bone type.The difference of alveolar septal cortical density in skeletal class III patients with different vertical bone types was statistically significan in the 4-5,5-6 regions of the upper jaw(including the buccal and palatal sides)and the 4-5,5-6 regions of the mandibular buccal side.Alveolar septal cortical density in high angle group lower than in low angle group.The bone cortical density of the maxillary buccal side of patients with skeletal class III is higher than that of the palatal side.In clinical practice,orthodontists should pay close attention to changes in bone cortical density in the area of mini-implant placement.In areas with low bone density,large diameter and long type micro-implants can be selected to improve the success rate of implantation;in areas with high bone density,the excessive heat generated during implantation should be avoided which will affect the success rate of implantation.In difficult cases,such as patients with severe craniofacial malformations or defects,each site should be fully evaluated before the implantation of the micro-implant.In addition,on the basis of previous experiments,for those orthodontic patients with severe alveolar bone resorption and defect,we may consider using bone tissue regeneration technology to repair alveolar bone in the future.