Stress distribution in the cervical region of an upper central incisor in a 3D finite element model

Abstract

The aim of this study was to evaluate the stress distribution in the cervical region of a sound upper central incisor in two clinical situations, standard and maximum masticatory forces, by means of a 3D model with the highest possible level of fidelity to the anatomic dimensions. Two models with 331,887 linear tetrahedral elements that represent a sound upper central incisor with periodontal ligament, cortical and trabecular bones were loaded at 45 o in relation to the tooth's long axis. All structures were considered to be homogeneous and isotropic, with the exception of the enamel (anisotropic). A standard masticatory force (100 N) was simulated on one of the models, while on the other one a maximum masticatory force was simulated (235.9 N). The software used were: PATRAN for pre-and post-processing and Nastran for processing. In the cementoenamel junction area, tensile forces reached 14.7 MPa in the 100 N model, and 40.2 MPa in the 235.9 N model, exceeding the enamel's tensile strength (16.7 MPa). The fact that the stress concentration in the amelodentinal junction exceeded the enamel's tensile strength under simulated conditions of maximum masticatory force suggests the possibility of the occurrence of non-carious cervical lesions such as abfractions.

Stress distribution on maxillary central incisorunder similar traumatic situations with different loading forces: a 3-D finite element analysis.

“…Concerning the validation of the finite element mesh, a simple complementary numerical method was used in an attempt to achieve a greater reliability of results and a confirmation of the cohesion of dental structures, along with the use of a commercial software already grounded in scientific literature. 5,10,12,13,15,16 Due to the application of the same impact direction, differences in stress distribution in the crown region of the tooth were not observed between the simulations. Some other factors were also similar, such as the lack of stress dissipation to the crown dentin, a fact that can be explained by the physicomechanical properties of dental enamel.…”

“…Some studies use a force of 800 N to simulate mild traumatic situations, which results, in most cases, in only enamel surface fractures. 5,[13][14][15][16] However, a study by Miura and Maeda showed that a force of 100 N, when applied horizontally on the buccal surface of the tooth, could already generate an avulsion. 16 The methodology of this study was based on other authors who used the finite element method with the same purpose of simulating the dentoalveolar structure.…”

“…29 Thus, according to Poiate et al, studies in which the PDL will be subjected to injury for a short period of time, as occurs in dentoalveolar trauma, linear elastic models are able to simulate the behavior of the PDL satisfactorily. 11,13 In view of the lack of data in the literature, the comparative values of maximum stress load supported by dental pulp do not allow one to confirm the significant pulp damage, although clinical studies suggest that mild trauma (e.g., concussion/ subluxation) may cause pulp necrosis. 30 Tanaka et al reported that dental pulp can withstand tensile/ compressive forces of 2.94 MPa, a value higher than the values found in both simulations, which was 0.45 MPa for the first simulation and 1.1 MPa for the second, thus suggesting that the applied forces were unable to cause pulp damage.…”

“…For this purpose, the ScanFE software created a thin layer of interposed elements between the two distinct layers of the model. This layer was included between the dentin and lamina dura with a thickness average of 0.2 mm, simulating the PDL 11,13,14 . However, the PDL is not uniformly thick.…”

“…This type of analysis was chosen, as it provides a more realistic simulation of the mechanism of dental trauma. 5,[13][14][15][16] The model verification was provided by the use of complementary numerical methods beyond the use of a commercial finite element software, ensuring the validation of the method itself, as well a correct application of boundary conditions, material properties, and load/force applications. 11,13,14 All steps of this study from image processing to the analysis and visualization of the results were performed using a Celeron 723 computer (Intel, Santa Clara, CA), equipped with a 250-Gb Hard Drive …”