Objectives

The purpose of the study was to compare the mvM stresses occurring in inlays, onlays and endocrowns made from different materials and their bonding with molars in a computer simulation of mastication.

Methods

The study was conducted using the finite elements method with contact elements. Sixteen 3D first molar models were created of a intact tooth – T; a tooth with a ceramic inlay – IN; a tooth with an onlay – ON; and a tooth with an endocrown – EN. The restorations were made of: Comp – resin nanoceramic; Hc – hybrid ceramic; Le – leucite ceramic; Dlit – lithium disilicate; and Zr – zirconia. Computer simulations of mastication were performed. The equivalent stresses according to the modified von Mises criterion (mvM) were calculated in model materials and contact stresses at the interface cement–dental tissue around the examined restorations.

Results

The highest equivalent mvM stresses were concentrated in buccal margins of inlays. The mvM stresses recorded in onlays were 1.6–5 times lower than those found in inlays, while in endocrowns they were 2.3–6.5 times lower. Around the onlays and endocrowns, in tooth structures and luting cement, mvM stresses were significantly lower compared to teeth restored with inlays. The tensile and shear contact stresses between inlays and teeth were several times lower than under another restorations.

The highest stresses (58.5 MPa) occurred in the zirconia inlay. The stresses observed in the enamel of a tooth restored with an INZr inlay were half those noted in INComp, and a third of those observed in cement. Tensile contact stresses at the interface between the INZr inlay and dental tissue were 4.5 times lower than in the INComp, and the shear stresses were more than 7 times lower.

Significance

The highest values and unfavorable of stress levels occurred in teeth restored with inlays. Cavities MOD in molars should be reconstructed with cusp-covering restorations. The endocrown in molars should withstand physiological loading.

The higher the modulus of elasticity of the restoration material, the higher the stresses in the restorations, while the lower stresses were observed in the tooth structures, luting cement and at the interface between the restoration and the dental tissue. Ceramic restorations should provide better protection and marginal seal of the reconstructed tooth than composite ones.

中文翻译：

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在咀嚼的计算机模拟-FEA中，比较了由各种材料制成的嵌体，嵌体和内冠的mvM应力及其与臼齿的粘合力。

目标

该研究的目的是在咀嚼的计算机模拟中，比较由不同材料制成的嵌体，嵌体和内冠中出现的mvM应力，以及它们与臼齿的粘合力。

方法

该研究是使用有限元方法与接触单元进行的。创建了完整牙齿的16个3D第一磨牙模型-T；陶瓷镶嵌的牙齿– IN；带有嵌体的牙齿-ON；和带有内冠的牙齿– EN。修复体由以下材料制成：Comp –树脂纳米陶瓷；Hc –混合陶瓷；Le –白云石陶瓷；Dlit –二硅酸锂；和Zr –氧化锆。进行了咀嚼的计算机模拟。在模型材料中计算了根据修正的冯·米塞斯（von Mises）准则（mvM）得出的等效应力，并在受检修复体周围的界面水泥-牙齿组织处产生了接触应力。

结果

最高的等效mvM应力集中在嵌体的颊缘。嵌体中记录的mvM应力比嵌体低1.6-5倍，而内冠中的mvM应力低2.3-6.5倍。与镶嵌物修复的牙齿相比，在镶嵌物和内冠周围，牙齿结构和黏结剂中，mvM应力明显更低。嵌体和牙齿之间的拉伸和剪切接触应力比其他修复体低几倍。

最高应力（58.5 MPa）出现在氧化锆镶嵌物中。用INZr嵌体修复的牙釉质中观察到的应力是INComp中记录的应力的一半，而在水泥中观察到的应力的三分之一。在INZr嵌体和牙齿组织之间的界面处的拉伸接触应力比在INComp中低4.5倍，而剪切应力则低7倍以上。

意义

最高值和不利的应力水平发生在镶嵌体修复的牙齿上。臼齿中的腔体MOD应该用尖端覆盖的修复体重建。臼齿中的内冠应该承受生理负荷。

修复材料的弹性模量越高，修复体中的应力越高，而在牙齿结构，粘固剂以及修复体与牙齿组织之间的界面处观察到的应力则越低。陶瓷修复体应比复合修复体提供更好的保护和对牙齿的边缘密封。