使用Cone Beam Computed Tomography研究矯正治療所產生之牙根吸收

Abstract

Many researches have proven that although root resorption also occurs in people who don't receive any orthodontic treatment; however, the incidence of those who received orthodontic treatment is significantly higher. When the root resorption gets seriously severe during the treatment, the problem of poor crown root ratio and periodontal bone stress concentration might be encountered. If orthodontic patients suffer from periodontal diseases in the years to come, they will experience periodontal bone loss, and thus, poor prognosis of the teeth. Together with the development of medical imaging technique, Cone Beam Computed Tomography (CBCT) has been widely used in the dental field. In orthodontic treatment, CBCT has been used for the diagnosis of impacted teeth, the evaluation of orthognathic surgery, assessment of micro-implant placed between root anatomical spaces, but there are few studies about assessment of root resorption which is derived from orthodontic treatments by using CBCT. Therefore, in this study we used CBCT to evaluate root resorption after seven months of orthodontic treatment, and we also studied the relationship between the changes of bone density around the roots and the comparison of the distance of root movements. Eight patient objects are selected from the patients in the Department of Orthodontics, China Medical University Hospital Medical Center, including five males and three females, aged ranging from 20-25. Observed images of root resorption after orthodontic treatment by the i-CAT CBCT after irradiation were converted to the appropriate coordinate system. The analytic software was Mimics. We studied, after seven months of orthodontic treatment, the relationship between variation of root length and root length changes in percentage, and the percentage of root tip moving distance and root length changes, relationship between bone density around roots before treatment and root length changes in percentage, and the changes of bone density around root and root length changes in percentage. The results showed that after seven-month orthodontic treatment, the average of root resorption in the right maxillary central incisor is 0.25 ± 0.16 mm, left maxillary central incisor is 0.32±0.34 mm, right maxillary lateral incisor is 0.39±0.32 mm, left maxillary lateral incisor is 0.48±0.19 mm, right maxillary canine is 0.18±0.19 mm, left maxillary canine is 0.19±0.14 mm. In summary, before the treatment, the thicker the bone density is, the less the root resorption occurs. The more bone density changes in the treatment, the less the root resorption is. When the moving distance is longer between the root tips, the observed root resorption gets more serious.