以錐狀射源電腦斷層影像觀測迷你豬下顎骨的生長發育

Abstract

研究人類下顎骨的生長發育文獻回顧中，目前尚未有實驗可以建立一套預測下顎骨生長發育的系統，且利用此系統探討顳顎關節疾病對於下顎骨生長發育的影響臨床配合生長治療的工作。 礙於醫學倫理問題，不適合長期以放射線照射法持續追蹤生長期兒童之下顎骨發展模式，參考實驗動物模型與和人類下顎骨生長之相似性，故選擇迷你豬作為本實驗長期觀察下顎骨生長模式之動物實驗模型當作訓練樣本的依據，因為豬的食物相跟人相似，且比猴子等靈長類容易取得當作實驗樣本。而本實驗以錐狀射源電腦斷層影像觀測迷你豬下顎骨的生長發育，以建立三維立體空間的動物模型。 實驗方法是選取兩隻李宋系迷你豬隻從滿四週起，每四週照一次錐狀射源電腦斷層直到滿一年，使用軟體堆疊出一年內豬頭骨的三維立體模型並收集生長參數。接下來在三維立體下顎骨模型標定點，以描述性統計描述各標定點的生長趨勢。 實驗結果顯示: (一)選定的九個標定點在第六七個月都是一個轉折點，不管是生長速度先遞增再遞減或先遞減再遞增，生長速度趨勢的轉換大多發生在第六七的月較多。(二)九個標定點大多在前六七個月生長量最大，比較有趣的是在標定點位在下顎骨前端的位置生長量在前後向(定義中的X軸)變化量最大，而標定點在下顎骨的最後下點的位置，往外(定義中的z軸向)往下(定義中的Y 軸向)長的生長量也遠大於往前(定義中的X軸向) 。 結論 : 僅以圖示目測及生長速度的值來比較可以推測迷你豬下顎骨在從第四週到第四十八週的生長，生長量變化以定義中的X軸最大，定義中的z軸向次之，定義中的Y軸向最小。

Introduction: In the literatures regarding to mandible growth, there is hardly any system to predict human mandible growth, through which the effects of temporomandibular disorders on growing mandible can be estimated. It is impossible to use longitudinal radiographic imaging to monitor human mandible growth, due to the ethics consideration. In this study we chose mini pig as the experimental animal because they have similar diet preference to the human, and easily available. Cone beam dental CT was used in this study to yield the volumetric images of the pigs’ mandibles at different time points. 3D reconstruction of the growing mandibles can then be built. Materials and Methods: The first volumetric images of the head were obtained from 4 weeks old of 2 mini pigs. Since then, the same CT images were performed again every 4 weeks till they were 1 year old. Nine anatomical reference points were then identified on the 3D reconstruction series for further analyses and descriptions. Results: The complete serial 3D reconstructions of the growing mandibles have been successfully obtained. Mandible growth velocities represented by the 9 points were not homogenous, namely some showed crescendo and other showed decrescendo patterns. These above-mentioned obvious growth velocities changes happened mainly at the time point of 5 or 6 months. The reference point in the chin point area showed most changes in the antero-posterior direction. The reference point in the gonial angle area showed most changes in the medio-lateral and supero-inferior directions. Conclusions: Between 4 weeks and 48 weeks old of the growing mini pig, the growth seems to be mostly happened in the antero-posterior direction, followed by the medio-lateral and supero-inferior directions. Complicated mathematical models of mandible growth could be built based on these serial 3D reconstructions.