3D透視法を用いた顎運動時の生体内3次元下顎運動学および機能点軌道の検討

In vivo three-dimensional mandibular kinematics and functional point trajectories during temporomandibular activities using 3d fluoroscopy.

抄録

目的:

3D透視法を用いて、顎関節活動中の下顎の3次元運動学および関連する終点軌道を測定し、それらの関係を定量化すること。

OBJECTIVES: To measure three-dimensional kinematics of the mandible and associated end-point trajectories and to quantify their relationships during temporomandibular joint activities using 3D fluoroscopy.

方法:

健康な若年者の開閉運動、側方滑走運動、突出-後退運動における下顎の運動とそれに関連する終点（切歯と両顆頭の外側極）の運動を、透視に基づく新しい3D測定法を用いて測定した。実験に基づくコンピュータシミュレーションにより、下顎の回転および並進の各成分の終点軌道への寄与を定量化した。

METHODS: A novel fluoroscopy-based 3D measurement method was used to measure motions of the mandible and the associated end points (i.e. incisors and lateral poles of both condyles) during open close, lateral gliding and protrusion-retraction movements in healthy young individuals. The contributions of each of the rotational and translational components of the mandible to the end-point trajectories were quantified through experiment-based computer simulations.

結果:

下顎の回転は最大開口容量の91％、最大側切歯移動の73％を占め、顆頭の並進は前突距離の99％に寄与することがわかった。切歯の軌跡は、開閉運動中の最大開口の最初の60％以内ではほぼ垂直であった。

RESULTS: The mandibular rotation was found to account for 91% of the maximal mouth-opening-capacity and 73% of the maximal lateral incisor movement, while the condylar translation contributed to 99% of the anterior protrusion distance. Incisor trajectories were nearly vertical within the first 60% of the maximal opening during the open-close movement.

結論:

開閉、側方滑走、突出-後退という3次元的なTI軌道の異なる下顎基本運動を行うために、両側で非対称な範囲を持つ同様の顆頭下方回転軌道が用いられた。下顎の回転は、切歯の主要な変位成分の大部分、すなわち、オープン-クローズ時には垂直方向、ラテラル-グライディング時には作業側方向への変位に寄与し、下顎の並進は、主にプロトージョン-リトラクション時の切歯の前方移動に寄与した。解剖学的制約のため、下顎の移動の自由度は制限されており、主に前後方向である。これは、口腔活動中の顎関節の制御と安定に役立つと考えられる。

CONCLUSIONS: Similar condylar downward rotation paths but with bilaterally asymmetrical ranges were used to perform basic mandibular movements of different targeted TI trajectories in three dimensions, that is open-close, lateral-gliding and protrusion-retraction. Mandibular rotations contributed to the majority of the principal displacement components of the incisor, that is vertical during open-close and towards the working-side-during lateral-gliding, while mandibular translation contributed mainly to the forward movement of the incisor during protrusion-retraction. Owing to the anatomical constraints, the freedom of mandibular translation is limited and mainly in the anteroposterior direction, which is considered helpful for the control and stability of the TMJ during oral activities.