全瓷冠内部应力分布规律的三维有限元研究

目的 运用有限元法分析全瓷冠的应力分布规律,为临床修复没计提供依据.方法 利用CT断层影像构建右下第一磨牙全瓷冠三维有限元模型.设计5种加载方式:垂直集中载荷600 N、垂直八点分布载荷600 N、垂直偏舌侧载荷600 N、10°偏颊侧载荷600 N、颊侧20°咀嚼载荷225 N,利用ANSYS软件分析各瓷层和界面的应力值大小.结果 5种加载方式下全瓷冠应力分布的相同之处:加载点可引起饰面瓷应力集中,沿载荷方向核瓷内表面拉应力集中.5种加载方式下全瓷冠应力分布的不相同之处:垂直集中载荷作用下,全瓷冠颈部肩台拉应力分布均匀;10°偏颊侧载荷仅使全瓷冠颊舌侧颈部肩台拉应力集中,最大值为32.25 MPa;颊侧20°咀嚼载荷引起全瓷冠颊侧、近中、远中颈部肩台拉应力集中,最大值为11.29 MPa.结论 制作全瓷冠应增加咬合接触面积,减少牙尖斜度,并提高颈部肩台陶瓷的抗拉能力.

Stress analysis of the all-ceramic crown with a numerical approach

Objective To analyze the stress distribution in all-ceramic crowns when it was subjected to load.Methods A 3D numerical model of the all-ceramic crown of the right mandibular first molar was generated from scanned CT images.Finite element analysis (FEA) was used to evaluate the stress distribution in the all-ceramic crown when it was subjected to 5 load conditions.Results Stress distributions under 5 loading conditions were obtained.Stress concentrations were generally found near the loading areas at the veneer and at the lower surface of the core beneath the loading areas.In the 5 loading conditions, it was found that when the crown was loaded with vertical concentrated load, the tensile stresses around the shoulder areas were uniform, while stress concentration with maximum of 32.25 MPa was found at the shoulder areas in lingual-buccal direction when loads were applied at an angle of 10° with the tooth axis on the buceal side.The masticatory load which was applied at 20° with the tooth axis on the buccal side would cause stress concentration at the shoulder in mesial-distal direction.The maximum value could reach 11.29 MPa.Conclusions The occlusal surface of the all-ceramic crown must be trimmed to increase multiple contact zones with the opposite surfaces in antagonist teeth to avoid excessive concentrated stress that may cause crown failure.