Comportamento mecânico de diferentes tipos de miniplacas para ancoragem esquelética no tratamento da mordida aberta anterior / Mechanical behavior of different miniplate designs for skeletal anchorage in the previus open bite

Situações clínicas que envolvam discrepâncias moderadas e que teriam como opção terapêutica o tratamento orto-cirúrgico, por meio da cirurgia ortognática, podem beneficiar-se da utilização da ancoragem esquelética buscando resultados satisfatórios e com menor morbidade ao paciente. O tratamento da mordida aberta anterior no paciente adulto é uma das situações em que as miniplacas podem oferecer uma ancoragem esquelética capaz de permitir o seu tratamento sem a realização da cirurgia ortognática. O objetivo deste trabalho foi verificar, por meio de análise por elementos finitos, distribuição de tensão e o comportamento de diferentes desenhos de miniplacas, por meio dastensões recebidas e deslocamento sofrido, simulando uma situação clínica de ancoragem esquelética para o tratamento de mordida aberta anterior no adulto. Em um modelo virtual foram aplicadas forças intrusivas de 2, 4 e 6N em molares superiores, tendo como ancoragem miniplacas com formatos T, Y, e I instaladas na região da crista zigomática alveolar. Verificou-se o deslocamento, tensão máxima principal e tensão de Von Mises, de acordo com o formato do dispositivo de ancoragem. As configurações das placas resultaram em diferentes intensidades de stress no osso, na placa e no deslocamento, porém essas tensões se localizaram sempre nas mesmas regiões dentro do limite fisiológico. A placa T obteve comportamento mais indesejado e a placa Y se mostrou mais próxima do ideal(AU)

Clinical situations that involve moderate discrepancies and that would have as a therapeutic option the ortho-surgical treatment, through orthognathic surgery, can benefit from the use of skeletal anchorage seeking satisfactory results and lower morbidity to the patient. The treatment of anterior open bite in the adult patient is one of the situations in which the miniplates can offer a skeletal anchorage capable of allowing its treatment without performing orthognathic surgery. The objective of this work was to verify, through finite element analysis, the bone stress and the behavior of different miniplate designs, through the tensions received and displacement suffered, simulating a clinical situation of skeletal anchorage for the treatment of anterior open bite in the adult. In a virtual model, intrusive forces of 2, 4 and 6N were applied in upper molars, and miniplates with T, Y, and I formats were anchored in the region of the zygomatic abutment. The displacement, main maximum voltage and voltage of Von Mises were checked according to the shape of the anchoring device. The plaque configurations resulted in different stresses in bone, plaque and displacement, but these stresses were always located in the same regions within the physiological limit. The T plate obtained more unwanted behavior and the Y plate showed to be closer to the ideal(AU)

In vitro evaluation of the resistance of three types of fixation to treat fractures of the mandibular angle.

The purpose of this study was to compare the mechanical resistance of three different plates used to treat fractures of the mandibular angle: a regular 4-hole plate, a longer 4-hole plate (both positioned using the Champy technique), and a 3-dimensional plate positioned over the oblique line. Three equal groups of replicas of human dentate mandibles made out of polyurethane resin were used (n=21 in each group). The force was applied perpendicular to the occlusal plane at a rate of 2mm/minute at three different points: the first molar on the sectioned side; the first molar on the contralateral side; and between the central incisors. This was followed by a resistance-to-load test. The two varying factors (type of plate and site-of-load application) were tested by analysis of variance, and probabilities of less than 0.05 were accepted as significant. There were no significant differences between the subgroups, or between the mean values of the different types of plates (p=0.925). The three types of plates showed similar mechanical behaviour, which showed that the 3-dimensional plates positioned over the oblique line can produce mechanical scores similar to those of conventional plates.

Diseño y análisis de placas cervicales anteriores mediante el método de los elementos finitos / Analysis and design of anterior cervical plates using the finite element method

En este trabajo se presenta el diseño y análisis de placas de fijación vertebral, utilizando el método de los elementos finitos. El objetivo de estas placas es devolver estabilidad a la columna vertebral y mejorar la fusión ósea, ofreciendo libertad en el posicionamiento de los tornillos para fijarlas al cuerpo vertebral. Para el diseño geométrico y el análisis fueron utilizados software ProEngineer© y Nastran©. Los esfuerzos que fueron obtenidos del análisis se mantuvieron dentro del rango elástico del material con el cual fueron simulados cada uno de los dos modelos de placas propuestas.

The analysis and design of cervical fixation plates using the finite element method is presented in this paper. Thepurpouse of these plates is to restore stability in the cervical spine and to improve the interbody fusion, allowing different screw positions to attach them to the vertebral body. The geometrical design and discretization were carried out by using ProEngineer© and Nastran© commercial software. The models of the mechanical devices are presented as well as the stress levels produced by the physiological loading. The results obtained from the analysis, showed stresses inside the elastic range in all the studied load cases.

Tratamiento de la espondilolistesis, con artrodesis posterior fijada con placas y tornillos transpendiculares tipo INO / Treatment of spondylolisthesis by posterior arthrodesis fixed by INO-type transpendicular screw-plating

El siguiente trabajo fue realizado en el Hospital Regional Presidente Juárez del ISSSTE, en la Ciudad de Oaxaca, Méx. en pacientes con espondilolistesis lumbosacra mayores de 14 años y menores de 65, con dolor y compromiso neurológico rebelde a tratamiento sin cirugía previa. Todos fueron tratados con fijación con placas y tornillos transpendiculares INO. Después de la cirugía nuestros resultados fueron excelentes en el 82 por ciento de los casos y las complicaciones que se presentaron no influenciaron en la mejoría de nuestros pacientes ya que en todos se llegó a la consolidación completa en forma satisfactoria. Concluimos que es un método seguro y eficaz con complicaciones casi nulas, que brinda al paciente una mejor calidad de vida