Measurement Of The Mandibular Posterior Area For Miniscrew Insertion In Different Skeletal Facial Types With CBCT

Objective: Application of CBCT at mandibular posterior area of different vertical bone for miniscrew of micro screw measurement analysis, To select the buccal cortical thickness of the corresponding cross-section and near- far and bucco-lingual bone width?Then dicuss the difference of micro planting area between high and low Angle in clinical orthodontic. To provide the reference for miniscrew insertion in the mandibular posterior area.Methods:From February 2014 to October 2015, 53 patients were chosen from the patients at the Orthodontic Department in hebei province stoma- tological hospital, age range for 18 to 40 years old.excluding the patients who have mandibular trauma, tumor, the adult retained deciduous teeth; get rid of periodontal diseases[1], which were divided into 2 groups, high and low angle[2]. All the patients were informed and agreed to take part in. All data was saved and imported into Invivo software. Use Invivo Dental 5.0 threedimensional cephalometric analysis software to present the reconstructed data in the form of three-dimensional images, and determine horizontal, sagittal and coronal plane in Scetion window at Invivo Dental 5.0 software. Then use the measurement function that comes with the software to measure.To select 2mm, 4mm, 6mm, 8mm, 10 mm fault from the top of the alveolar crest in the the mandibular posterior area(second premolar and first molar, first molar and second molar), the buccal cortical thickness of the corresponding cross-section and near- far and bucco-lingual bone width were measured.Input all data into SPSS 21.0 software, statistical analysis.Results:1 With the increase of distance alveolar ridge crest,the low-angle group and high- Angle group mesial and distal direction between the second premolar and the first molar,the first molar and second molar, nearly far in the near- far and bucco-lingual bone width showed a trend of increase.2 In hypodivergent group, the minimum distance between the mesial and distal roots, the minimum buccal cortical thickness and the minimum alveolar bone thickness were all in the 2mm section under the alveolar ridge crest between the second premolar and the first molar. The maximum distance between the mesial and distal roots and the maximum buccal cortical thickness were in the 10 mm section between the first molar and the second molar, and the maximum alveolar bone thickness was in the 8mm section between the first molar and the second molar. In hyperdivergent group, the minimum distance between the mesial and distal roots, the minimum buccal cortical thickness were in the 2mm section between the second premolar and the first molar, and the minimum alveolar bone thickness was in the 2mm section between the first molar and the second molar. The maximum distance between the mesial and distal roots, the maximum buccal cortical thickness and the maximum alveolar bone thickness were all in the 10 mm section between the first molar and the second molar.3 In hypodivergent group and hyperdivergent group, there were significant differences in the thickness of the buccal cortical thickness and alveolar bone thickness in each section. As to the distance between the mesial and distal roots, there was statistical difference in the 2mm section in hyperdivergent group, while there were no significant differences in hypodivergent group.4 Longitudinal comparison of hypodivergent group and hyperdivergent group showed that: the distance between mesial and distal roots were statistically significant. Buccal cortical bone thickness and alveolar bone thickness were statistically significant between the second premolar and the first molar in both hypodivergent and hyperdivergent group.While between the first molar and the second molar, there was no significant difference ony between 8mm and 10 mm section.5 Comparison of hypodivergent group and hyperdivergent group showed that: between the second premolar and the first molar, there were significant differences in the distance between mesial and distal roots as well as the thickness of the buccal cortical thickness in 2mm, 4mm, 6mm, 8mm section. While there were no significant differences alveolar bone thickness in each section. Between the first molar and the second molar, there were significant differences in the distance between mesial and distal roots in 2mm, 4mm sectio, and there were significant differences in the thickness of the buccal cortical thickness in 4mm section. However, there were no significant differences alveolar bone thickness in each section.Conclusion:1 Low Angle between the second premolar and the first molar, micro screw implant from the alveolar crest of 4 mm, 6 mm, 8 mm, 10 mm cross-section implanted relatively safe, low Angle between the group of the first molar and second molar, micro screw implant from the alveolar crest of 2 mm, 4 mm, 6 mm, 8 mm, 10 mm cross-section relative safety.2 High Angle between the second premolar and the first molar, micro screw implant from the alveolar crest of 8 mm, 10 mm cross-section implanted relatively safe,High Angle between the group of the first molar and second molar, micro screw implant from the alveolar crest of 6 mm, 8 mm, 10 mm cross-section relative safety.3 High Angle relative to the low Angle group between the second premolar and the first molar, the near- far and buccal cortical thickness are smaller. When choice micro screw implanting area in clinical,the vertical skeletal patterns should be considered. High Angle has bigger risk than low Angle.