CBCT Evaluation Of Bone Mineral Density In Adult Micro-implant Implantation Sites

Objective: To measure the alveolar bone mineral density(BMD) of the right posterior area of different vertical facial skeletal types in patients who need for orthodontic treatment by cone beam CT(CBCT)technique, and through statistical analysis of data, to find the differences and regularity. Aimed at helping orthodontic doctors understand the differences and features of alveolar BMD in adults with different vertical facial skeletal types, in order to provide certain reference basis to clinical orthodontics treatment and implant anchorage.Methods:54 cases who have CBCT datas were selected from department of dentistry of Weifang peoples’ hospital between March 2014 to October 2015. According to the mandibular plane angle measurement of the lateral, the ratio of posterior facical height and anterior facical height. all cases were divided into 3 groups,each has 18 cases. The BMD of the alveolar spacer region from canine teeth to the second molar were detected by a same person with CBCT technique.The measuring sites were 4--7 mm from the top level of the alveolar ridge, and the measuring project included the BMD of maxillary buccal bone cortex,maxillary cancellous,maxillary lingual bone cortex,mandible buccal bone cortex,mandible lingual bone cortex, and mandible cancellous.ANOVA was used to analyse the data by SPSS17.0,setting P<0.05 as statistically significant difference.Results:(1) In the datas of all the mesuring sites of high-angle group,there were statistical differences between premolar region and molar region exccept for those in mandible lingual bone cortex(P<0.05).(2) In the datas of all the mesuring sites of normal-angle group,there were statistical differences between premolar region and molar region exccept for those in mandible buccal bone cortex and mandible lingual bone cortex(P<0.05).(3) In low-angle group,the BMD of maxillary buccal bone cortex,maxillary lingual bone cortex,mandible buccal bone cortex,mandible lingual bone cortex, and mandible cancellous at molar region were statistically higer than those at premolar region(P<0.05),but for the maxillary cancellous was just on the contrary,the BMD at molar region was lower than that at premolar region(P<0.05).(4) The maximum BMD of premolar region and molar region in all the 3 groups occured in mandible buccal bone cortex.(5) In high-angle group, the BMD of mandibular alveolar bone at different measuring site were higher than those of maxillary alveolar bone at their opposite measuring site(P<0.05),promoting that the BMD of mandible buccal bone ortex,mandible lingual bone cortex, and mandible cancellous are higher than those of maxillary buccal bone cortex,maxillary lingual bone cortex and maxillary cancellous.In normal-angle group, there were statistical differences except for the maxillary cancellous and mandible cancellous in premolar region 4-5,molar region 5-6/6-7(P<0.05).It promoted that the BMD of mandible buccal bone cortex and mandible lingual bone cortex are higher than those of maxillary buccal bone cortex and maxillary lingual bone cortex, the BMD of mandible cancellous in premolar region 3-4 is higher than that of maxillary cancellous.In low-angle group, there were statistical differences except for the lingual bone cortex in premolar region 3-4 and molar region(P<0.05).It promoted that the BMD of mandible buccal bone cortex and mandible cancellous are higher than those of maxillary buccal bone cortex and maxillary cancellous, the BMD of mandible lingual bone cortex in premolar region 4-5 is higher than that of maxillary lingual bone cortex.(6) In premolar regions,the BMD in high-angle group were lower than those in low-angle group except for maxillary buccal bone cortex4-5,maxillary lingual bone cortex and maxillary lingual bone cortex3-4(P<0.05);the BMD in normal-angle group were higher than those in low-angle group except for maxillary buccal bone cortex 3-4 and mandible lingual bone cortex 4-5(P<0.05), and the BMD of maxillary lingual bone cortex and maxillary cancellous were the highest in the 3 groups;the BMD of mandible buccal bone cortex and mandible cancellous in low-angle group were higher than those in the other 2 groups(P<0.05);the BMD of cancellous bones in high-angle group were the lowest(P<0.05).(7) n molar regions,the BMD of maxillary cancellous,maxillary lingual bone cortex,mandible buccal bone cortex,mandible lingual bone cortex and mandible cancellous in high-angle group were lower than those in the other 2 groups(P<0.05);the BMD of maxillary cancellous and mandible cancellous in normal-angle group were higher than those in the other 2 groups(P<0.05).Conclusions:(1) There were significant differences in different measuring sites of different regions in different groups except for the mandible lingual bone cortex in high-angle group and mandible buccal bone cortex and mandible lingual bone cortex in normal-angle group.(2) In premolar regions, the BMD 0f maxillary buccal bone cortex and mandible lingual bone cortex in high-angle group were higher than those 2 other groups;the BMD of maxillary lingual bone cortex in normal-angle group were higher than those 2 other groups;the BMD of mandible buccal bone cortex in low-angle group were higher than those in the other 2 groups.In molar regions, the BMD of maxillary cancellous, maxillary lingual bone cortex, mandible buccal bone cortex, mandible lingual bone cortex and mandible cancellous in low-angle group were higher than those in the other 2 groups.(3) The BMD of maxillary cancellous in normal-angle group was higher than that of the other 2 groups; The BMD of mandible cancellous in low-angle group was higher than that of the other 2 groups; so the BMD of cancellous bone in the high-angle group was the lowest.