前歯部のコーンビームCT画像による三次元自動歯軸

摘要

歯の長軸を表す歯軸は，歯の基本的形態基準軸であり， 橋義歯•部分床義歯における支台歯や鉤歯の軸面方向決定 の指針，力学的観点からの咬合についての診断，支台歯形 成時における歯髄腔形態の予測，矯正治療の診断等におい て重要である.歯軸はこれまでに，解剖学的および矯正学 的に検討されてきた.しかし，これまでの歯軸の多くは二 次元的歯軸が用いられており，その定義も「歯頸部付近に 重点を置き，歯の中央部を縦に通る直線を歯軸とするとい う概念」を参考に，検者により目視で定める場合がほとん どである.%This study presents a novel method for automatically calculating the three-dimensional tooth axis based on in vivo Cone-Beam Computed Tomography (CBCT). In this study, 60 teeth were obtained, comprising 20 central and lateral incisors, and canines of 5 human participants, respectively. Human in vivo images were obtained using CBCT at a spatial resolution of 0.183 mm3. The tooth axis (PC-A) was automatically calculated using principal component (PC) analysis of the segmented tooth and mandible. In the experimental results using the 60 teeth, the average relative angular errors between the tooth axes (T-A) manually specified by three dentists and the PC-A automatically calculated by the proposed method were 2.6 ±1.2。 for central incisors,1.6 ± 0.9° for lateral incisors, and 2.2 ±1.3° for canines.