Objective

The goal of this study was to evaluate the stress distribution in a tooth/restoration system according to the factors “amount of dental remnant” (3 levels) and “restorative material” (2 levels).

Methods

Three endodontically treated maxillary molars were modeled with CAD software for conducting non-linear finite element analysis (FEA), each with a determined amount of dental remnant of 1.5, 3, or 4.5 mm. Models were duplicated, and half received restorations in lithium disilicate (IPS e.max CAD), while the other half received leucite ceramic restorations (IPS Empress CAD), both from Ivoclar Vivadent (Schaan, Liechtenstein). The solids were imported to analysis software (ANSYS 17.2, ANSYS Inc., Houston, TX, USA) in STEP format. All contacts involving the resin cement were considered no-separation, whereas between teeth and fixation cylinder, the contact was considered perfectly bonded. The mechanical properties of each structure were reported, and the materials were considered isotropic, linearly elastic, and homogeneous. An axial load (300 N) was applied at the occlusal surface (triploidism area). Results were determined by colorimetric graphs of maximum principal stress (MPS) on tooth remnant, cement line, and restoration.

Results

MPS revealed that both factors influenced the stress distribution for all structures; the higher the material’s elastic modulus, the higher the stress concentration on the restoration and the lower the stress concentration on the cement line. Moreover, the greater the dental crown remnant, the higher the stress concentration on the restoration. Thus, the remaining dental tissue should always be preserved.

Significance

In situations in which few dental remnants are available, the thicker the restoration, the higher the concentration of stresses in its structure, protecting the adhesive interface from potential adhesive failures. Results are more promising when the endocrown is fabricated with lithium disilicate ceramic.

中文翻译：

---

内向修复体：残余牙齿和修复材料对应力分布的影响

客观的

这项研究的目的是根据“牙齿残余量”（3个级别）和“修复材料”（2个级别）的因素来评估牙齿/修复系统中的应力分布。

方法

使用CAD软件对三个经牙髓治疗的上颌磨牙进行建模，以进行非线性有限元分析（FEA），每个确定的牙齿残余量为1.5、3或4.5 mm。复制模型，一半接受二硅酸锂修复体（IPS e.max CAD），另一半接受白云石陶瓷修复体（IPS Empress CAD），均来自Ivoclar Vivadent（列支敦士登，Schaan）。将固体以STEP格式导入到分析软件（ANSYS 17.2，ANSYS Inc.，休斯敦，美国，美国）中。所有涉及树脂胶粘剂的接触都被认为是不可分离的，而在牙齿和固定圆柱体之间，接触被认为是完美结合的。报告了每种结构的机械性能，并将材料视为各向同性，线性弹性和均质材料。在咬合面（三倍体区域）施加轴向载荷（300 N）。结果通过比色图在牙齿残余物，骨水泥线和修复体上的最大主应力（MPS）来确定。

结果

MPS揭示了这两个因素都会影响所有结构的应力分布。材料的弹性模量越高，修复体上的应力集中就越大，而水泥线上的应力集中就越低。而且，牙冠残留物越大，修复体上的应力集中就越大。因此，应始终保留剩余的牙齿组织。

意义

在几乎没有残留牙的情况下，修复体越厚，其结构中的应力集中就越高，从而保护了胶粘剂界面免受潜在的胶粘剂故障的影响。当内冠由二硅酸锂陶瓷制成时，结果会更有希望。