咬合面の高さがインプラント支持単冠後面の応力分布に及ぼす影響の三次元有限要素解析

[Three-dimensional finite element analysis of influence of occlusal surface height on stress distribution around posterior implant-supported single crown].

• Xu Zhao
• Lei Zhang
• Jian Sun
• Zhen-yu Yang
• Qiu-fei Xie

抄録

目的:

下顎のインプラント支持後面単冠の咬合面の高さが骨組織の応力に及ぼす影響を評価する．

OBJECTIVE: To evaluate the effect of the occlusal surface height of a mandibular posterior implant-supported single crown on stress in bone tissues.

研究方法:

右下第2小臼歯を補うインプラント支持単冠，近心・遠心天然歯，歯根膜，歯槽骨，荷重剛体，アーモンドのアナログ食品の3次元有限要素モデルを作成した．FDI(Federation Dentaire International)システムを用いて、第一小臼歯、第二小臼歯、第一大臼歯を44、45、46で表した。歯冠の3つの咬合面高さを調査した。(1)通常の高さ，(2)15μmの高さの減少，(3)30μmの高さの減少である。模型への荷重は，単一の歯冠に最大咬合力（44×280N，45×360N，46×480N）と平均咬合力（44×140N，45×180N，46×240N）の単独荷重，複合荷重（最大咬合力を3.7MPaの一様荷重に変換して剛体の上に載せる。複合荷重（最大咬合力を剛体上で3.7MPaの均一荷重に変換し，咬合面上の点に接触させる），アナログアーモンド様食品荷重（模擬食品咀嚼時の平均咬合力を1.67MPaの均一荷重に変換し，咬合面上の点に接触させる）を行いました。

METHODS: Three-dimensional finite element models of the implant-supported single crown replacing the missing right lower second premolar, mesial and distal natural teeth, periodontal membrane, alveolar bone, loaded rigid body and analog food of almond were established. Using the Federation Dentaire International (FDI) system, the first premolar, the second premolar and the first molar were represented with 44, 45, 46. Three occlusal surface heights of the crown were studied: (1) normal height; (2) 15 μm reduction in height; (3) 30 μm reduction in height. The models were loaded by independent loading with maximal occlusal force(44 by 280 N, 45 by 360 N, and 46 by 480 N) and average occlusal force(44 by 140 N, 45 by 180 N, and 46 by 240 N)on the single crown; combined loading (maximal occlusal force transformed into uniform load of 3.7 MPa on top of rigid body, in contact with points on the occlusal surface), and analog almond-like food loading (average occlusal force transformed into uniform load of 1.67 MPa in simulated food chewing, in contact with points on the occlusal surface).

結果:

単独荷重時の最大咬合力では，44，45，46番付近の骨組織のフォンミーゼス応力のピーク値は82.57MPa，45.26MPa，27.79MPa，平均咬合力では41.28MPa，22.63MPa，13.89MPaであった。複合荷重下では，正常咬合面高さ群と比較して，30μm内包群の45，46，44で，フォンミーゼス応力のピーク値がそれぞれ4.6 MPa，0.84%減少し，7.52 MPa，20.04%増加し，1.8 MPa，5.84%減少した。食物負荷時のフォンミーゼス応力ピーク値は，30μm内包群の45，46，44でそれぞれ0.34MPa，1.62%減少，1.11MPa，2.66%増加，0.06MPa，0.54%増加した。

RESULTS: For maximal biting force under independent loading, Von Mises stress peak values in bone tissues around 44, 45, and 46 were 82.57 MPa, 45.26 MPa and 27.79 MPa; For average biting force, peak values were 41.28 MPa, 22.63 MPa and 13.89 MPa. Under combined loading, compared with the normal occlusal surface height group, Von Mises stress peak values decreased 4.6 MPa, by 0.84%; increased 7.52 MPa, by 20.04%, and decreased 1.8 MPa, by 5.84%, for 45, 46, and 44 in the 30 μm infra-occlusion group, respectively. Under food loading, Von Mises stress peak values decreased 0.34 MPa, by 1.62%; increased 1.11 MPa, by 2.66%; and increased 0.06 MPa, by 0.54%, and for 45, 46, and 44 in the 30 μm infra-occlusion group, respectively.

結論:

本研究の制限内で，インプラント支持単冠の咬合面高さが30μm以内であれば，ピーク値に有意な差は認められなかった．

CONCLUSION: Within the limitation of this study, within 30 μm reduction of the occlusal surface height of implant-supported single crown, no significant difference of the peak values was observed.