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首页> 外文期刊>The Journal of Prosthetic Dentistry >Rationalization of incisor shape: experimental-numerical analysis.
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Rationalization of incisor shape: experimental-numerical analysis.

机译：门牙形状的合理化：实验数值分析。

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STATEMENT OF PROBLEM: Moving from the posterior segment in the anterior direction within the dental arch, the process of "incisivization" takes place. The occlusal table is gradually replaced by an incisal edge that has the function of cutting. PURPOSE: This study considers these genetically controlled changes by using strain gauge measurements and finite element analyses to rationalize the clinical and biologic advantages of incisal form. A direct clinical link in the common esthetic procedure of anterior veneering is expected. MATERIAL AND METHODS: Six maxillary incisors were mounted in a positioning device and equipped with 2 strain gauges bonded to the palatal surface: gauge 1 (G1) in the concavity and gauge 2 (G2) on the cingulum. A 50 N load was applied on the palatal side of the incisal edge, perpendicular to the long axis of the tooth. Displacement of the load tip and the palatal strain were recorded after successively removing one third, two thirds, and the total thickness of the facial enamel. The same experiment was reproduced with the finite element method (FEM). Four additional experimental designs were tested with the FEM by simulating the progressive thinning and elimination of palatal enamel and a thickened palatal lobe. Surface tangential stresses and local strain in the area corresponding to gauges 1 and 2 were calculated from the postprocessing files. RESULTS: The FEM was validated by experimental results considering both displacement of the load tip ( approximately 120 +/- 30 microm) and tangential surface strain at G1/G2. Recorded strains were always higher in the concavity when compared with the cingulum; high tensile strains were recorded at G1 after the total removal of the facial enamel. The entire facial surface was submitted to compressive forces. Subsequent compressive stresses were higher ( approximately 150 MPa) when facial enamel was thin or when the palatal enamel was removed. However, their absolute value never reached the elevated and potentially harmful tensile stresses measured in the palatal concavity, especially in the absence of facial enamel (272 MPa). Multiple experimental cracks were generated in the remaining palatal enamel as a consequence of stress redistribution. However, smooth and convex surfaces with local enamel bulk such as the cingulum, the marginal ridges, and the facial cervical third of the anatomic crown showed the lowest stress level. The optimal configuration with regard to the stress pattern was given by the modified natural tooth that exhibited thick palatal enamel and a mostly convex palatal surface. CONCLUSIONS: Palatal concavity that provides the incisor with its sharp incisal edge and cutting ability proved to be an area of stress concentration. This shortcoming can be compensated by specific areas that feature thick enamel such as the cingulum and the marginal ridges. When enamel is worn or removed from the facial surface, its replacement should be carried out by using materials with properties similar to enamel to restore the original biomechanical behavior of the tooth.
机译：问题陈述：在牙弓内从后段沿前方向移动，发生了“切牙化”过程。咬合台逐渐被具有切割功能的切缘代替。目的：本研究通过使用应变仪测量和有限元分析来考虑这些遗传控制的变化，以合理化切牙形式的临床和生物学优势。预期在前饰面的常见美学过程中有直接的临床联系。材料和方法：将六个上颌切牙安装在定位装置中，并配备2个与gauge表面粘合的应变仪：在凹处的应变仪1（G1）和在扣带上的应变仪2（G2）。在切缘的the侧垂直于牙齿的长轴施加50 N的载荷。依次去除三分之一，三分之二和面部牙釉质的总厚度后，记录负荷尖端的位移和pa应变。相同的实验通过有限元方法（FEM）进行。用FEM通过模拟渐进性变薄和消除and釉和增厚的lo裂，对另外四个实验设计进行了测试。从后处理文件中计算出对应于量规1和2的区域中的表面切向应力和局部应变。结果：通过考虑载荷尖端的位移（大约120 +/- 30微米）和G1 / G2处的切向表面应变的实验结果验证了有限元法。与扣带相比，凹形中记录的应变总是更高。完全清除面部瓷釉后，在G1处记录到高拉伸应变。整个面部表面都受到压缩力。当面部牙釉质较薄或去除pa釉质时，随后的压应力较高（约150 MPa）。但是，它们的绝对值从未达到在lat凹处测得的升高的且潜在有害的拉伸应力，特别是在没有面部珐琅质（272 MPa）的情况下。由于应力重新分布，在剩余的pa釉质中产生了多个实验裂纹。但是，具有局部牙釉质的光滑和凸出的表面（例如扣带，边缘脊和解剖冠的三分之一的面部颈椎）的应力水平最低。关于应力模式的最佳配置是由改性天然牙提供的，该天然牙表现出thick厚的牙釉质和大部分为凸面的pa表面。结论：为切牙提供锋利的切缘和切开能力的Pala骨凹陷被证明是应力集中的区域。此缺陷可以通过具有浓厚珐琅质的特定区域（例如扣带和边缘脊）来弥补。当磨损或从面部去除牙釉质时，应使用性能与牙釉质相似的材料来更换牙釉质，以恢复牙齿的原始生物力学性能。

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