Department of Dental Materials and Prosthodontics, São Paulo State University (Unesp), Institute of Science and Technology, Av. Eng. Francisco José Longo, n° 777, Jardim São Dimas, 12245-000 São José dos Campos, SP, Brazil.
Department of Restorative Dentistry, São Paulo State University (Unesp), Institute of Science and Technology, Av. Eng. Francisco José Longo, n° 777, Jardim São Dimas, 12245-000 São José dos Campos, SP, Brazil.
Dent Mater. 2018 Oct;34(10):1466-1473. doi: 10.1016/j.dental.2018.06.012. Epub 2018 Jun 21.
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).
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 4.5mm. 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 (300N) 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.
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.
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.
本研究旨在评估根据“牙体剩余量”（3 个水平）和“修复材料”（2 个水平）这两个因素，牙体-修复体系统的应力分布情况。
使用 CAD 软件对 3 颗上颌磨牙进行建模，以进行非线性有限元分析（FEA），每颗磨牙的牙体剩余量分别为 1.5、3 或 4.5mm。对模型进行复制，一半用锂硅二硅酸玻璃陶瓷（IPS e.max CAD，义获嘉伟瓦登特公司，列支敦士登沙安）进行修复，另一半用透锂长石增强瓷（IPS Empress CAD，义获嘉伟瓦登特公司）进行修复。将固体导入分析软件（ANSYS 17.2，ANSYS Inc.，德克萨斯州休斯顿）的 STEP 格式中。所有涉及树脂水门汀的接触均被认为是无分离的，而在牙齿和固定柱之间的接触则被认为是完全结合的。报告了每种结构的机械性能，并且材料被认为是各向同性、线弹性和均匀的。在咬合面（三倍体区域）施加 300N 的轴向载荷。通过牙体剩余、水门汀线和修复体的最大主应力（MPS）的彩色图谱来确定结果。
MPS 表明，两个因素都影响了所有结构的应力分布；材料弹性模量越高，修复体的应力集中越高，水门汀线的应力集中越低。此外，牙冠剩余量越大，修复体的应力集中越高。因此，应始终保留剩余的牙体组织。
在牙体剩余量较少的情况下，修复体越厚，其结构的应力集中越高，从而保护粘结界面免受潜在的粘结失败。当使用锂硅二硅酸玻璃陶瓷制作内冠时，结果更有希望。
