下顎大臼歯のバイオメカニクスに及ぼすアクセスキャビティの影響：有限要素法による解析

Effect of access cavities on the biomechanics of mandibular molars: a finite element analysis.

抄録

はじめに:

本研究は、有限要素解析（FEA）を用いて、多様な歯内腔を有する下顎第一大臼歯（MFM）の破壊抵抗を予測することを目的とした。

INTRODUCTION: This study aimed to predict the fracture resistance of a mandibular first molar (MFM) with diverse endodontic cavities using finite element analysis (FEA).

方法:

天然歯(NT)と歯内療法を施した4本のMFMの5つの実験用有限要素モデルを作成した．歯内療法モデルには，従来の歯内療法空洞（TEC）と，低侵襲歯内療法空洞（MIE）（ガイド歯内療法空洞（GEC），収縮歯内療法空洞（CEC），トラス歯内療法空洞（TREC）を含む）を用いた．垂直方向に最大600Nの咬合力，垂直方向および側方に225Nの咀嚼力を負荷した．フォンミーゼス応力（VM）分布と最大VM応力を算出した。

METHODS: Five experimental finite element models representing a natural tooth (NT) and 4 endodontically treated MFMs were generated. Treated MFM models were with a traditional endodontic cavity (TEC) and minimally invasive endodontic (MIE) cavities, including guided endodontic cavity (GEC), contracted endodontic cavity (CEC) and truss endodontic cavity (TREC). Three loads were applied, simulating a maximum bite force of 600 N (N) vertically and a normal masticatory force of 225 N vertically and laterally. The distributions of von Mises (VM) stress and maximum VM stress were calculated.

結果:

NTモデルの最大VM応力は、通常の咀嚼力下で最も低かった。歯内療法モデルでは、GECモデルのVM応力分布はNTモデルに最も類似していた。GECおよびCECの最大VM応力は，TRECおよびTECの最大VM応力よりも低かった．垂直荷重下では、TRECモデルの最大VM応力が最も高く、横荷重下ではTECモデルの最大VM応力が最も高かった。

RESULTS: The maximum VM stresses of the NT model were the lowest under normal masticatory forces. In endodontically treated models, the distribution of VM stress in GEC model was the most similar to NT model. The maximum VM stresses of the GEC and CEC models under different forces were lower than those of TREC and TEC models. Under vertical loads, the maximum VM stresses of the TREC model were the highest, while under the lateral load, the maximum VM stress of the TEC model was the highest.

結論:

GECを用いた歯の応力分布はNTに最も類似していた．GECおよびCECはTECと比較して耐欠損性を維持しやすいが，TRECは耐欠損性の維持には限界がある．

CONCLUSION: The stress distribution of tooth with GEC was most like NT. Compared with TECs, GECs and CECs may better maintain fracture resistance, TRECs, however, may have a limited effect on maintenance of the tooth resistance.