Bone Density And The Cortical Bone Thickness In Different Skeletal Facial Types Adolescent Evaluated With Cone Beam Computerized Tomography

OBJECTIVE:Different parts of the bone mineral density and thickness of cortical bone are measured and analyzed with different facial types in young patients alveolar bone by Cone-beam CT,in order to provide a reference for clinical orthodontic treatment design and selection of implant anchorage.METHODS:Select60cases in chronological order from the Nanchang University Affiliated Stomatological Hospital outpatients whose met the inclusion criteria.According to the mandibular plane angle measurement of the lateral film,the patients are divided into high angle, average angle and low angle of the three groups, n=20.After the agreements of patient,we use CBCT to scan craniomaxillofacial and make three-dimensional reconstruction on the computer, the maxillary and mandibular anterior region, the canine area, the first molar area and molar alveolar bone mineral density and buccal cortical thickness are measured through the invivo dental software. At last, statistical analysis made to the result.RESULTS:1. Bone mineral density1.1The cortical bone density of the high angle group ranged between898and1357Hounsfield units (HU).The highest cortical bone density area was observed in the buccal cortical bone of the mandibular molar area, the lowest cortical bone density area was observed in the buccal cortical bone of the maxilla incisor area.The cancellous bone density of the high FMA group ranged between279and692Hounsfield units (HU).The highest cancellous bone density area was observed in the mandibular incisor area, the lowest cancellous bone density area was observed in the the maxilla molar area.There are significant differences in different measurement areas (P<0.05) 1.2The cortical bone density of the average angle group ranged between899and1484Hounsfield units (HU),the highest bone density area was observed in the buccal cortical bone of the mandibular premolar area,the est bone density area was observed in the buccal cortical bone of the maxilla incisor area.The cancellous bone density of the high angle group ranged between378and670Hounsfield units (HU). The highest cancellous bone density area was observed in the mandibular incisor area. The highest bone density area was observed in the buccal cortical bone of the maxilla molar area.there are significant differences in different measurement areas.(P<0.05)1.3The cortical bone density of the low angle group ranged between927and1665Hounsfield units (HU),the highest cortical bone density area was observed in the buccal cortical bone of the lower molar area,the lowest cortical bone density area was observed in the buccal cortical bone of the upper incisor area.The cancellous bone density of the high angle group ranged between434and849Hounsfield units (HU).The highest cancellous bone density area was observed in the lower incisor area. The lowest bone density area was observed in the buccal cortical bone of the lower molar area. In addition to the low-angle group of cancellous bone between the mandibular four regional are no differences, there are significant differences between the different measurement areas of the same group.(P<0.05)1.4In addition to the upper anterior buccal cortex, the anterior region under the tongue side of cortical bone and the maxillary canine area lingual bone cortex,the Cortical bone density data analysis found that the low-angle group was higher than the average angle group,and the latter was higher than the average angle group. Significant differences was found among the three groups.(P<0.05)2. Thickness of cortical bone2.1The cortical bone thickness of the high angle group ranged between0.44and2.39millirmeter,and the thickest was found at the7mm level in the lower molar area and the thinnest was found at the3mm level in the upper incisor area. At the same level of measurement,it has been observed that a difference in the cortical bone thickness exists for the four regions,with the anterior region<the canine area<the premolar area<the molar area (P<0.05). At the different level of measurement, the cortical bone thickness in maxillary molar area with5mm<3mm<7mm (P<0.05). However,it has been found that3mm<5mm<7mm(P<0.05) in the other measurement areas.2.2The cortical bone thickness of the average angle group ranged between0.45and2.85millirmeter. The cortical bone thickness of the high angle group ranged between0.44and3.11millirmeter.These two group had the same thickness and thinnest areas to high angle group.And had the same difference whether in different measurement areas or at the different measurement level.2.3Among the three groups there are no difference at the3mm measurement level in the maxillary and mandibular anterior region, maxillary and mandibular canine area, maxillary premolar area and maxillary molar area(P>0.05).But in other measurement areas, significant differences have been found that high angle<average angle<low angle(P<0.05).At the5mm and7mm measurement level,no difference was found in the maxillary and mandibular anterior region, mandibular canine area, maxillary premolar area and maxillary molar area(P>0.05), significant differences have been found that high angle<average angle<low angle(P<0.05)in other meas-urement areas.CONCLUSION:1. Cancellous bone density in the different different facial typles have significan-tdifferences.The low angle group has highest bone density,and the high angle group has the least bone density. The results showed that the teeth movement in patients of high angle group is easier,it needs enhance the anchorage.2.There are significant differences in cortical bone density of different areas.It’s larger in the areas of molars and premolars than in anterior teeth. The results indicate that use an increased diameter implant to remain the stability is needed in anterior area. The stability of implant is better when insert in mandibular molars area.But the self-tipping implant should be choosen and decrese the diameter.temperature to increase the success rate for the larger cortical bone density.3. There are significant differences in cortical bone thickness of different areas. Except the cortical bone thickness in the area of maxillary molars is5mm<3mm<7mm (P<0.05), others is3mm<5mm<7mm (P<0.05).The results indicate that the site selection of implant need contact the apical aspect of alveolar as possible,and5mm level in the maxillary molar area should avoid.4. There are significant differences in cortical bone thickness of different skeletal facial profile. The cortical bone thickness of mandibular molars area is high angle group<average angle group<low angle group.It indicates that the implant inserted in patients of low mandibular plane angle is a higher success rate.