ABSTRACT
INTRODUCTION: Deepbites can be corrected by intrusion of mandibular anterior teeth. Direct anchorage with miniscrews simplifies complex tooth movements; however, few studies have reported their use for mandibular anterior intrusion. The purpose of this study was to evaluate, by means of the finite element method, initial tooth displacement and periodontal stress distribution using various mandibular anterior intrusion mechanics. Miniscrews were used as skeletal anchorage devices. METHODS: Cone-beam computed tomography scans were used for 3-dimensional reconstruction of the mandible and the mandibular anterior dentition. Models included the 4 incisors with or without the canines. After all surrounding periodontal and bony structures were determined brackets, segmental archwires, and miniscrews were added. Finite element studies were performed to assess initial tooth displacement and periodontal stress distribution with multiple intrusion force vectors. Changes in the location of the miniscrews and loading points on the archwire created 14 scenarios. RESULTS: Minimum buccolingual displacements, a uniform distribution of periodontal stress, and overall group intrusion for both 4-tooth and 6-tooth scenarios were best achieved when applying distointrusive vectors. The highest peaks of periodontal stress were observed when the force was directed at the corners of the segmental archwire. It was found that, in addition to distointrusive vectors, 4 loading points on the archwire were necessary for pure intrusion and uniform distribution of periodontal stress in the 6-tooth scenarios. CONCLUSIONS: The simulations in this study suggest that group intrusion of all 6 mandibular anterior teeth might be achieved by applying distointrusive vectors. Inserting a pair of miniscrews distal to the canine roots, 1 screw per side, and directing 4 loading points on the archwire generates uniform periodontal stress distribution and minimum buccolingual displacements. Local conditions, such as narrow bone width and attached gingiva level, play significant roles in the clinical viability of the proposed virtual scenarios.
Subject(s)
Dental Implants , Finite Element Analysis , Imaging, Three-Dimensional/methods , Incisor/surgery , Mandible/surgery , Orthodontic Anchorage Procedures/instrumentation , Tooth Movement Techniques/instrumentation , Tooth Movement Techniques/methods , Adult , Alveolar Process , Biomechanical Phenomena , Computer Simulation , Cone-Beam Computed Tomography/methods , Elastic Modulus , Female , Humans , Image Processing, Computer-Assisted/methods , Incisor/pathology , Malocclusion, Angle Class I/therapy , Mandible/pathology , Mechanical Phenomena , Models, Biological , Orthodontic Appliance Design , Orthodontic Brackets , Orthodontic Space Closure/methods , Orthodontic Wires , Stress, MechanicalABSTRACT
Las úlceras por presión son las complicaciones secundarias más comunes a una lesión medular, las cuales ponen en riesgo tanto la salud como la vida de quienes las padecen. Las úlceras por presión más comunes en lesionados medulares aparecen en la región pélvica, principalmente en las tuberosidades isquiáticas (TI's). Una estrategia usada en la clínica es medir la presión generada entre el paciente y la superficie donde se encuentra para evaluar el riesgo que representa dicha superficie para el desarrollo de úlceras por presión sin embargo, este tipo de mediciones superficiales no garantizan que la presión en los tejidos internos subyacentes a prominencias óseas sea inocua. Con el fin de estudiar los mecanismos de formación de úlceras por presión, se realizó el análisis de un modelo de pelvis y tejido subyacente por medio del Método de los Elementos Finitos (MEF). De esta manera se puede estudiar el comportamiento de las TI's sobre su tejido circundante, así como analizar los efectos biomecánicos que provocan las úlceras. Se construyó el modelo computacional por medio de un software de CAD (Computing Aided Design) de la pelvis a partir de cortes tomográficos. El modelo fue exportado al software COMSOL y se analizaron seis casos de estudio: un análisis de la pelvis sobre bloques de tejido sano y cinco casos más, los cuales simulan lesiones en el tejido con distintas profundidades, representando úlceras superficiales e internas. Los resultados mostraron que los puntos de máximo esfuerzo, en todas las pruebas, se localizan justo debajo de la TIs además se encontró que las lesiones internas presentan mayores esfuerzos y deformaciones, los cuales pueden ser precursores de daño en el tejido.
Pressure ulcers are the most common secondary complication to a spinal cord injury, which endanger both health and life of the patients who suffer them. The most common pressure ulcers in spinal cord injuries occur in the pelvic region, mainly in the ischial tuberosities (ITs). A strategy used in clinic is to quantify the pressure generated between the patient and the surface, in order to assess the risk posed by that surface for developing pressure ulcers. Despite this, this type of surface measurements does not guarantee that pressure in the internal tissues underlying to bony prominences, to be safe. In order to study the mechanisms of formation of pressure ulcers, an analysis of a model of the pelvis and its underlying tissue was performed using the Finite Element Method (FEM). By this means we can study the behavior of ITs on its surrounding tissue, and at the same time, we analyze the biomechanical effects those cause ulcers. The computational model of the pelvis was built from tomographic slices using CAD software (Computing Aided Design). The model was exported to the finite element software COMSOL and six study cases were analyzed: an analysis of the pelvis on healthy tissue blocks and five more cases, which simulate tissue injury with different depths, representing surface and internal ulcers. The results showed that the maximum stress points in all tests are located just below the ITs it was also found that internal injuries present higher stresses and strains, which can be precursors of tissue damage.
