Comportamiento Mecánico de un Premolar Humano Sano Sometido a Fuerzas Funcionales y Disfuncionales en un MEF / Mechanical Behavior of a Healthy Human Premolar Subjected to Functional and Dysfunctional Forces in a FEM

El propósito de este estudio fue analizar el comportamiento mecánico de la estructura dental sana de un primer premolar inferior humano sometido a fuerzas funcionales y disfuncionales en diferentes direcciones. Se buscó comprender, bajo las variables contempladas, las zonas de concentración de esfuerzos que conllevan al daño estructural de sus constituyentes y tejidos adyacentes. Se realizó el modelo 3D de la reconstrucción de un archivo TAC de un primer premolar inferior, que incluyó esmalte, dentina, ligamento periodontal y hueso alveolar considerando tres variables: dirección, magnitud y área de la fuerza aplicada. La dirección fue dirigida en tres vectores (vertical, tangencial y horizontal) bajo cuatro magnitudes, una funcional de 35 N y tres disfuncionales de 170, 310 y 445 N, aplicadas sobre un área de la cara oclusal y/o vestibular del premolar que involucró tres contactos estabilizadores (A, B y C) y dos paradores de cierre. Los resultados obtenidos explican el fenómeno de combinar tres vectores, cuatro magnitudes y un área de aplicación de la fuerza, donde los valores de esfuerzo efectivo equivalente Von Mises muestran valores máximos a partir de los 60 MPa. Los valores de tensión máximos se localizan, bajo la carga horizontal a 170 N y en el proceso masticatorio en la zona cervical, cuando la fuerza pasa del 60 %. Sobre la base de los hallazgos de este estudio, se puede concluir que la reacción de los tejidos a fuerzas funcionales y disfuncionales varía de acuerdo con la magnitud, dirección y área de aplicación de la fuerza. Los valores de tensión resultan ser más altos bajo la aplicación de fuerzas disfuncionales tanto en magnitud como en dirección, produciendo esfuerzos tensiles significativos para la estructura dental y periodontal cervical, mientras que, bajo las cargas funcionales aplicadas en cualquier dirección, no se generan esfuerzos lesivos. Esto supone el reconocimiento del poder de detrimento estructural del diente y periodonto frente al bruxismo céntrico y excéntrico.

SUMMARY: 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.

Comparison of frictional resistance between passive self-ligating brackets and slide-type low-friction ligature brackets during the alignment and leveling stage.

BACKGROUND: To compare the frictional resistance between passive self-ligating brackets and conventional brackets with low-friction ligature under bracket/archwire and root/bone interface during dental alignment and leveling. MATERIAL AND METHODS: A tridimensional model of the maxilla and teeth of a patient treated with conventional brackets, and slide ligatures was generated employing the SolidWorks modeling software. SmartClip self-ligating brackets and Logic Line conventional brackets were assembled with slide low-friction ligatures, utilizing archwires with different diameters and alloys used for the alignment and leveling stage. Friction caused during the bracket/archwire interface and stress during the bone/root interface were compared through a finite element model. RESULTS: SmartClip and Logic Line brackets with slide elastomeric low-friction elastomeric ligature showed similar frictional stress values of 0.50 MPa and 0.64 MPa, respectively. Passive self-ligating brackets transmitted a lower load along the periodontal ligament, compared to conventional brackets with a low-friction ligature. CONCLUSIONS: Slide low-friction elastomeric ligatures showed frictional forces during the bracket/archwire interface similar to those of the SmartClip brackets, while the distribution of stresses and deformations during the root/bone interface were lower in the passive self-ligating brackets. Key words:Orthodontic friction, finite element analysis, orthodontic brackets, orthodontic wires.

Metodología alternativa para elaborar modelos geométricos de anatomía dental / Alternative methodology to elaborate geometrical models of dental anatomy

Se pretende proponer una metodología alternativa para elaborar modelos geométricos de anatomías dentales para estructuras de dientes incisivos y caninos, y crear modelos CAD apropiados para un posterior estudio por método. Se describe la metodología aplicándola a la construcción de un Incisivo maxilar lateral izquierdo, donde posteriormente se analiza, a modo de ejemplo, el comportamiento del elemento creado bajo una carga de 200 N; esta carga genera un desplazamiento de 27 pm y un esfuerzo Von Mises máximo de 92.588 MPa.

The aim of this article is to propose an alternative methodology to elaborate geometrical models of dental anatomy for incisors and canines structures, and to create appropriate CAD models for a further numerical method study. The methodology is described applying it to the construction of a maxillary left lateral incisor. Then the crated element is analyzed, as an example, under a load of 200 N. This load generates a displacement of 27 pm and a maximum Von Mises stress of 92.588 MPa.