Research Article Numerical Analysis of Masticatory Forces on a Lower First Molar considering the Contact between Dental Tissues Rosa Alicia Hernández-Vázquez , Beatriz Romero-Ángeles, Guillermo Urriolagoitia-Sosa, Juan Alejandro Vázquez-Feijoo, Ángel Javier Vázquez-López, and Guillermo Urriolagoitia-Calderón Instituto Politécnico Nacional, Escuela Superior de Ingeniería Mecánica y Eléctrica, Sección de Estudios de Posgrado e Investigación, Avenida Instituto Politécnico Nacional s/n, Edificio 5, 2do. Piso, Col. Lindavista, Unidad Profesional Adolfo López Mateos “Zacatenco”, 07320 Ciudad de México, Mexico Correspondence should be addressed to Rosa Alicia Hernández-Vázquez; alyzia.hv@esimez.mx Received 12 December 2017; Accepted 25 February 2018; Published 10 April 2018 Academic Editor: Jan Harm Koolstra Copyright © 2018 Rosa Alicia Hernández-Vázquez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The aim of the present work is to identify the reactions of the dental organs to the different forces that occur during chewing and the transcendence of the union and contact maintained by the dental tissues. The study used a lower first molar biomodel with a real morphology and morphometry and consisting of the three dental tissues (enamel, dentin, and pulp) each with its mechanical properties. In it, two simulations were carried out, as would the process of chewing a food. One of the simulations considers the contact between the enamel and the dentin, and the other does not take it into account. The results obtained differ significantly between the simulations that consider contact and those that do not, establishing the importance of taking this contact into account. In this way, the theories that establish horizontal and lateral occlusion forces are present during the functional chewing process which are viable to be correct. The case studies carried out present not only the reasons for the failure of enamel but also the failure of the restoration materials used. This reflection will allow the development of more adequate materials, mechanical design of prostheses, implants, and treatment. 1. Introduction The analysis of stress distribution in the dental organs under the action of occlusal loads entails a high complexity prob- lem. This is due to the nonhomogeneity of various tissues that integrate their particular morphology, as each of these tissues has distinct mechanical and biological properties as well as a specific physiology, which constitutes a dynamic and specialized biomechanical system [1]. During mastica- tion, the occlusal forces generated by the masticatory mus- cles, mainly the masseter, are applied to the dental organs, the enamel being the tissue that receives directly these loads. Dental enamel is a highly specialized organic tissue, made up of a complex crystalline structure. The hydroxyapatite prisms that compose it are ordered in the form of packages surrounded by organic matter, forming a mineralized matrix which gives it a property extremely hard but fragile [2]: that is, on its own, the enamel is extremely brittle; thus, it frac- tures easily. However, as it is supported by the dentine, the loads that arrive at the enamel are transmitted to this one, which, having an organic matrix greater than enamel support (type I collagen), gives it more elasticity. This situation improves the support of the normal loads transmitted by the enamel, allowing a better resistance to it. The contact zone between both tissues, enamel and dentin, is not a smooth and regular area. It is described as an irregular scalloped boundary, where one can see pro- trusions of dentin projecting towards the enamel. Dentin and enamel are being formed by the same kind of cells (mineralized collagen and hydroxyapatite), so they are Hindawi Applied Bionics and Biomechanics Volume 2018, Article ID 4196343, 15 pages https://doi.org/10.1155/2018/4196343