3種類の修復材料を用いて最小限に作製したエンドクラウンの抵抗破壊：3次元有限要素解析

Resistance fracture of minimally prepared endocrowns made by three types of restorative materials: a 3D finite element analysis.

抄録

歯内療法を受けた歯で，垂直方向の咬合高さが失われていたり，臨床上の歯冠長が不十分な場合には，薄いエンドクラウン修復物が適用されることが多かった。厚さ1mm，歯髄腔の深さ2mmのエンドクラウン修復を行った下顎臼歯部の模型を作製し，FEA ANSYS v18.0に取り込んだ．長石（Mark2），二ケイ酸リチウム（EMAX），溶岩石（LU）の3種類のCAD/CAM材料を割り当て，モデル内の修復物の全咬合（FO），咬合中心（OC），中心窩（CF），頬側溝（BG），中頬側カスプ（MC）に5つの荷重圧子を負荷した．FO群で荷重されたLUエンドクラウンを除く5種類の荷重で，薄いエンドクラウンのMinPSとMaxPSは歯牙組織のそれよりも有意に高かった。荷重の接触面が小さいほど，MaxPSとMinPSが高かった。MCのMaxPSとMinPSが最も高く，次いで修復物のBGとCFであった。歯牙組織の応力分布では，OC，CF，BG荷重下で，LUエンドクラウンのMaxPSはエナメル質外縁部に蓄積し，Mark2およびEMAXエンドクラウンのMaxPSは象牙質室壁に蓄積したのに比べて有意に高かった。今回のFEA研究の制限内では，LUエンドクラウンはMark2やEMAXよりも多くの応力を歯牙組織に伝達し，中頬側咬頭荷重時のエンドクラウン修復物および歯牙組織の最大主応力は，中心窩および頬側溝荷重時のそれよりも高かった。

A thin endocrown restoration was often applied in endodontically treated teeth with vertical bite height loss or inadequate clinical crown length. A model of mandibular molars made by endocrown restoration with 1 mm thickness and 2 mm depth of pulp chamber was constructed and imported into FEA ANSYS v18.0 software. The three CAD/CAM materials, feldspathic (Mark2), lithium disilicate (EMAX), and lava ultimate (LU), were assigned, and the five load indenters were loaded on the full occlusal (FO), occlusal center (OC), central fossa (CF), buccal groove (BG), and mesiobuccal cusp (MC) of restoration in the model. The MinPS and MaxPS of the thin endocrown were significantly higher than those of tooth tissue in five types of loads except for the LU endocrown loaded in the FO group. The smaller the contact surface of the load was, the higher MaxPS and MinPS were. MaxPS and MinPS of the MC were the highest, followed by the BG and CF in the restoration. In the stress distribution of tooth tissue, MaxPS in the LU endocrown accumulated at the external edge of enamel and was significantly higher than MaxPS in Mark2 and EMAX endocrown concentrated on the chamber wall of dentin under OC, CF and BG loads. Within the limitations of this FEA study, the LU endocrown transferred more stress to tooth tissue than Mark2 and EMAX, and the maximum principal stress on endocrown restoration and tooth tissue at the mesiobuccal cusp load was higher than that at the central fossa and buccal groove load.