| 摘要: | 許多研究都已經證實，雖然牙根吸收在未接受矯正治療的人也會發生，但是接受矯正治療的人發生率明顯較高。當矯正過程中發生牙根吸收變短的情況較嚴重時，可能會產生不佳的牙冠牙根比例，周圍骨應力集中等問題。如果將來患者產生牙周疾病，造成牙齒周圍骨喪失(periodontal bone loss)的情況，則牙齒的預後將更差。隨著醫學影像的進步，牙科用電腦斷層掃描(Cone Beam Computed Tomography, CBCT)也漸漸的在牙科領域被廣泛運用。在矯正治療方面，CBCT被運用在阻生牙齒之診斷、正顎手術、評估牙根間置放微植體的解剖空間等，但是較少研究討論使用CBCT來評估矯正治療所造成的牙根吸收。因此本研究將利用CBCT來探討矯正治療七個月過程牙根吸收的情況，同時與牙根周圍骨密度變化、牙根移動距離做比較，探討之間的相關性。
本研究以中國醫藥大學附設醫院牙醫部齒顎矯正科八位門診病患為研究對象，其中包含五名男性及三名女性，年齡介於20-25歲之間，由i-CAT CBCT照射後經座標系統轉換後之影像來觀測矯正治療後產生牙根吸收的情況。研究分析軟體為Mimics，分別研究七個月矯正治療後，牙根長度變化量與牙根長度變化百分比，牙根尖移動距離與牙根長度變化百分比之關係，治療前牙根周圍骨密度與牙根長度變化百分比之關係，牙根周圍骨密度改變量與牙根長度變化百分比之關係。
結果顯示經過七個月的矯正治療，八個受試者平均牙根吸收在上顎右正中門牙為0.25±0.16 mm，上顎左正中門牙為0.32±0.34 mm，上顎右側門牙為0.39±0.32 mm，上顎左側門牙為0.48±0.19 mm，上顎右犬齒為0.18±0.19 mm，上顎左犬齒為0.19±0.14 mm。以整體趨勢而言，治療前牙根周圍骨密度越大者，其牙根吸收較輕微。矯正治療過程中牙根周圍骨密度改變量較多者，牙根吸收的情況較輕微。當牙根尖移動距離越大者，牙根吸收的情況將越嚴重。
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. |
