以大鼠動物測試低能量雷射治療矯正牙齒移動及固持之效用

Abstract

矯正療程過長常是患者決定是否接受治療的考量因素之一，而治療效率的提高除了運用適當的力學設計將力量有效率地傳導至牙齒上，以避免力學副作用產生於錨定上，牙齒移動速度的生理限制更是重要因子。低能量雷射已有臨床實驗証實可加速牙齒移動速度，使用特殊參數設定，提供一個無明顯副作用的非侵入性療法。另外矯正完成後穩定度的維持也是重要課題，矯正後牙周組織的回彈常是矯正復發原因之一，若能加速牙周組織重塑，應可減少矯正復發率。本實驗以大鼠模型測試波長970 nm，500 mW之脈衝波對矯正牙齒移動(n=28)及矯正復發(n=30)的影響。根據不同能量設定及照射時間，實驗中所採用之低能量雷射在間隔三天的照射下可有效加速牙齒移動且移動量與照射劑量成正比。實驗初期密集照射則無法呈現加速效果。從顯微斷層掃瞄及組織磨片皆可觀察到受力臼齒牙根間及周圍有骨吸收現象，而螢光標定也顯示雷射照射後有較高的骨質重塑。本實驗同時建立大鼠矯正復發模型，從結果發現在牙齒移動後的固定期間照射低能量雷射可加速受力臼齒牙根間處之骨生成，使得復發率降低。 在本實驗中少數樣本之雷射照射處有異常骨增生現象，從組織磨片及HE染色片可觀察到樣本於實驗晚期在該處有大量的骨質堆積。此現象是否為低能量雷射可能的副作用還有待後續實驗証實。另外以高劑量設定下照射未受力側之齒槽骨，可見骨表面產生不規則狀，而同一側牙根間之骨組織也有較強的螢光標定，可見低能量雷射可加速基礎骨代謝, 然而詳細作用機制仍不明。

Treatment duration is one of the major determinants for patients seeking orthodontic treatment. To avoid long treatment time, orthodontists have to design sound mechanics meeting the anchorage demands and delivering appropriate force system to the tooth and its supporting tissues. However, the more crucial factors related to the treatment efficiency may lie in the individual biological response which is still largely unknown, to the force system which orthodontists regularly delivered. Low level laser with specific power setting has been shown as a non-invasive adjunctive treatment without obvious side effect for facilitating orthodontic tooth movement (OTM) in some clinical studies. Relapse after orthodontic treatment is also an important issue, rebound of compressed gingival tissue can cause unwanted tooth movement. Therefore, long-term retention is recommended which causes patient’s extra effort for compliance. Low level laser has been approved to facilitate collagen remodeling, and this possibly can further reduce the relapse rate. In the first part of this study, 28 rats were divided into four groups by different irradiation protocols to determine the effect of 970 nm low level laser with 500 mW power setting in pulsed mode on OTM. After 15-day experiment, the amount of tooth movement was significantly increased in 3 day-interval irradiation groups in a dose dependent manner. Early intense irradiation could not facilitate orthodontic tooth movement. From μCT, ground sections, and HE staining sections all show regional demineralization around the moving tooth and in furcation area when low level laser delivered. In the second part of this study, 30 rats was divided into four groups with different treatment protocol (according to the different duration of fixation period) to determine the effect of the same laser setting on relapse. The relapse rate was reduced on the third day after removing appliance. The ground sections show more bone formation during fixation period in laser group which indicated stimulated bone synthesis rate. We found buccal bone bulging on laser site in 3 samples, which may indicate the potential side effect of 970 nm laser with high energy setting (500 mW, 120s/session, pulsed mode), which needs to be confirmed by further research. With the same setting, the laser was applied to non-treated alveolar process on rat mandible, some surface irregularity was found from μCT image and decalcified sections, and ground sections also show areas of increasing bone labeling. Though it was not a consistent finding, it still warrants further investigation. The results of this study revealed that 970 nm low level laser with 500 mW output and pulsed mode can increase the speed of OTM and reduced the relapse rate.