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The purpose of this study was to analyze the mechanical behavior of the healthy dental structure of a human mandibular first premolar subjected to functional and dysfunctional forces in different directions. It was sought to understand, under the contemplated variables, the areas of stress concentration that lead to structural damage of its constituents and adjacent tissues. The 3D model of the reconstruction of a CT file of a lower first premolar was made, which included enamel, dentin, periodontal ligament and alveolar bone considering three variables: direction, magnitude and area of the applied force. The direction was directed in three vectors (vertical, tangential and horizontal) under four magnitudes, one functional of 35 N and three dysfunctional of 170, 310 and 445 N, applied to an area of the occlusal and/or buccal face of the premolar that involved three stabilizing contacts (A, B and C) and two closing stops. The results obtained explain the phenomenon of combining three vectors, four magnitudes and an area of force application, where the values of effective equivalent Von Mises stress show maximum values from 60 MPa. The maximum tension values are located under the horizontal load at 170 N and in the masticatory process in the cervical area, when the force exceeds 60%. Based on the findings of this study, it can be concluded that the reaction of tissues to functional and dysfunctional forces varies according to the magnitude, direction, and area of application of the force. The stress values turn out to be higher under the application of dysfunctional forces both in magnitude and in direction, producing significant tensile stresses for the dental and cervical periodontal structure, while under functional loads applied in any direction, no damaging stresses are generated. This supposes the recognition of the power of structural detriment of the tooth and periodontium against centric and eccentric bruxism. [ABSTRACT FROM AUTHOR]

Several studies report that the type of food directly influences the kinematic patterns of mastication. The aim of this study was to analyze and compare the chewing cycles of adult and fully dentate participants during the mastication of foods of different texture and hardness (peanuts and carrots) using 3D electromagnetic articulography. Eleven healthy participants (5 men; 6 women), 31.9 ± 5.2 years old, were evaluated. By means of 3D electromagnetic articulography, the mastication of two test foods (peanuts and carrots) was recorded. The data associated to mandibular movement were processed with MATLAB® obtaining different parameters--masticatory frequency in cycles per second, mandibular descent and ascent rate, area of the projections of each masticatory cycle in the three planes of space--which were compared according to type of food and sex of the participants. Statistically significant differences were found between the areas of the masticatory cycles in the horizontal plane according to type of food, being greater for carrots (P=.003). Likewise, statistically significant differences were detected between the sagittal areas of the cycles between men and women, being greater in women (P=.042). Our results agree with other studies that affirm that the texture of the food influences the kinematic characteristics of the masticatory cycles. [ABSTRACT FROM AUTHOR]

Approximately eleven thousand years ago humans beings went from feeding on animals they hunted or fished and fruits and plants they gathered, to crops they could grow through agriculture. This change dramatically altered the shape of the skull, particularly the face, which became more gracile, and also reduced the contribution of key nutrients. Along with industrialization, there was great deterioration of oral health. Leaving behind the hunter-gatherer diet has even been attributed to the origins of dental malocclusions, as masticatory stress was reduce, and reducing the size of the maxilla and mandible with respect to the teeth. Nowadays, there is greater awareness in the general population regarding personal care and their surroundings. Diets that exclude certain types of foods such as animal products are becoming more prevalent. The vegetarian diet has several characteristics that can affect metabolism, particularly the bones, as did the change from hunter-gatherer to agriculture in the past. The present review seeks to analyze the changes of the human diet, from the nutritional and mechanical point of view and how these have affected the shape of the face. This in order to understand the possible effects of the introduction of restrictive type feeds, such as the vegetarian diet in the body, particularly in facial anatomy. [ABSTRACT FROM AUTHOR]