数値流体力学モデルを用いた内歯根吸収歯における潅流現象の検討．

Examination of Irrigant Flow on a Tooth With Internal Root Resorption by Using a Computational Fluid Dynamics Model.

抄録

目的:

本研究では，内歯根吸収を起こした単根歯における歯内治療用薬剤の流れを検討した．

OBJECTIVE: This study investigated the flow of an endodontic irrigant in a single-rooted tooth with internal root resorption (IRR).

研究方法:

内歯根吸収のある中切歯のシミュレーションを作成し，30G針を用いたイリゲーションを行った．灌流液の流体パターンは，数値流体力学モデルを用いて評価した．さらに，根管内の針の挿入深さと歯根吸収の大きさが，流体の流れと壁せん断応力（WSS）の値に及ぼす影響を評価した。なお，IRRは根管開口部の直下に設置した。

METHODS: A simulation of a prepared central incisor with internal root resorption was created and irrigation with a 30-G needle was performed. The fluid pattern of the irrigant was evaluated using a Computational Fluid Dynamics model. In addition, the effects of the needle-insertion depth in the root canal and the size of root resorption on the fluid flow and the wall shear stress (WSS) values were assessed. The IRR was placed immediately below the canal orifice.

結果:

作業長から1mmの位置に針を配置した場合，吸収腔内での灌流液の洗い出しは不十分であった。一方，吸収腔のやや上に針を配置した場合，吸収腔内での灌流液の循環は顕著であった。さらに、針を欠損部の少し上に配置した場合、吸収腔壁のWSSの計算値が著しく高くなった（いずれの場合も約20倍）。作業長から1mmのところに針を置いた場合、WWSの平均値と最大値は3Paから51Paであったが、IRRに沿って針を置いた場合は、55Paから528Paであった。

RESULTS: Inadequate irrigant washout was observed inside the resorption cavity when the needle was positioned 1 mm from the working length while placing the needle slightly above the resorption cavity resulted in significant irrigant circulation inside the resorption cavity. Moreover, when the needle was placed slightly above the defect, the calculated WSS values in the resorption cavity walls were significantly higher (approximately 20 times higher in every case). In cases where the needle was placed 1 mm from the working length, the average and maximum WWS values were between 3 Pa and 51 Pa, while in cases where the needle was placed coronal to the IRR, the values were between 55 Pa and 528 Pa. The radius of the resorption cavity did not affect the irrigant flow patterns.

おわりに:

内歯根吸収症例の歯内療法では，根管をよりよく脱落させるために，針先を吸収腔の少し上に配置して補完的な灌流を行うべきである。

CONCLUSION: During the endodontic treatment of cases with internal root resorption, complementary irrigations with the needle tip placed slightly above the resorption cavity should be followed to better debride the root canal.