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Call number: LD2668 .T4 1963 S66 / Master of Science

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Master / Master of Dental Surgery

Os bisfosfonatos têm sido indicados para o tratamento de doenças ósseas líticas. Atualmente, seu emprego terapêutico aumentou e com ele os efeitos adversos, sendo um dos mais importante a indução da osteonecrose dos maxilares, uma complicação de difícil tratamento e solução. Até o presente, não se sabe ao certo qual o mecanismo de desenvolvimento da osteonecrose e nem qual deve ser o melhor tratamento estabelecido perante essa manifestação. Este trabalho teve como objetivo avaliar o efeito do alendronato sódico sobre a viabilidade e proliferação de osteoblastos e fibroblastos em cultura. Foram utilizados osteoblastos-símile linhagem OSTEO 1 e fibroblastos de mucosa bucal humana linhagem FMM1. Após serem submetidos aos testes de citotoxicidade com concentrações do alendronato sódico variando de 10-2M a 10-8M os fibroblastos apresentaram diminuição significante de viabilidade celular apenas na concentração de 10-2M (p<0,01). Os osteoblastos demonstraram viabilidade celular no grupo controle significantemente maior que todos os demais grupos; o grupo tratado com o alendronato na concentração de 10-4M apresentou viabilidade celular semelhante a de todos os grupos, exceto o grupo de concentração 10-2M e a viabilidade celular dos demais grupos foi semelhante entre si (p<0,01). As concentrações de alendronato sódico superiores a 10-5M impediram a proliferação dos osteoblastos. Foi possível concluir que o alendronato sódico é citotóxico para células osteoblastos-símile e fibroblastos em cultura em função de sua concentração. Os fibroblastos são menos sensíveis a concentrações maiores de alendronato sódico que os osteoblastos. / Bisphosphonates have been therapeutically used for the management of lytic bone diseases. Their use has been increased nowadays and besides that associated adverse effects have been amplified. Jaw osteonecrosis induced by this drug is perhaps the most important complication because of the great morbidity and difficulty to deal with. Until now the physiopathology of osteonecrosis remains unclear and the treatment that should be established is uncertain. This study aimed to evaluate the effect of sodium alendronate a bisphosphonate used for the treatment of osteoporosis on the viability and proliferation of osteoblasts and fibroblasts in culture. Osteoblast-simile from the lineage OSTEO1 and a human oral mucosa fibroblasts from the lineage FMM1 were used. After being subjected to tests with concentrations of sodic alendronate ranging from 10-8M to 10-2M fibroblasts showed a significant decrease in cell viability at the concentration of 10-2M (p < 0.01). Osteoblasts showed that the cell viability in the control group was significantly higher than all other groups, the group treated with alendronate at a concentration of 10-4M had similar cell viability with all groups except the group of 10-2M concentration and the cell viability of other groups was similar between groups (p < 0.01). The concentrations of alendronate greater than 10-5M prevented the proliferation of osteoblasts. It was possible to conclude that alendronate is cytotoxic to osteoblast-símile cells and fibroblasts in culture due to its concentration. The fibroblasts are less sensitive to higher concentrations of alendronate than osteoblasts.

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

A series of experiments are described which explore the relationship between biomechanical properties and the control of jaw movement in speech. This relationship is documented using kinematic analyses in conjunction with a mathematical model of jaw motion and direct measures of jaw stiffness. / In the first experiment, empirical and modeling studies were carried out to examine whether the nervous system compensates for naturally occurring forces acting on the jaw during speech. As subjects walk or run, loads to the jaw vary with the direction and magnitude of head acceleration. While these loads are large enough to produce a measurable effect on jaw kinematics, variation in jaw position during locomotion is shown to be substantially reduced when locomotion is combined with speech. This reduction in jaw motion is consistent with the idea that in speech, the control of jaw movement is adjusted to offset the effects of head acceleration. Results of simulation studies using a physiologically realistic model of the jaw provide further evidence that subjects compensate for the effects of self-generated loads by adjusting neural control signals. / A second experiment explores the idea that a principle mechanical property of the jaw---its spring-like behavior, or stiffness---might influence patterns of kinematic variation in speech movements. A robotic device was used to deliver mechanical perturbations to the jaw in order to quantify stiffness in the mid-sagittal plane. The observed stiffness patterns were non-uniform, with higher stiffness in the protrusion-retraction direction. Consistent with the idea that kinematic patterns reflect directional asymmetries in stiffness, a detailed relationship between jaw kinematic variability and stiffness was observed---kinematic variability was consistently higher under conditions in which jaw stiffness was low. Modeling studies suggested that the pattern of jaw stiffness is significantly determined by jaw geometrical properties and muscle force generating abilities. / A third experiment examines the extent to which subjects are able to alter the three-dimensional pattern of jaw stiffness in a task-dependent manner. Destabilizing loads were applied to the jaw in order to disrupt the ability of subjects to maintain a static jaw posture. Subjects adapted by increasing jaw stiffness in a manner that depended on the magnitude and, to a more limited extent, direction of the destabilizing load. The results support the idea that stiffness properties can be controlled in the jaw, and thus may play a role in regulating mechanical interactions in the orofacial system.

External loads, such as those due to the orientation of body segments relative to gravity, affect the extent to which control signals result in the achievement of desired goals. The degree to which subjects adjust control signals to compensate for loads provides a measure of what the nervous system knows about forces affecting motion and gives an indication of the complexity of control signals needed for voluntary movement. In the present study, we have explored the hypothesis that subjects take no account of the orientation of the head relative to gravity when making jaw movements during speech. We used a simulation model of the jaw to predict the kinematic effect of using a single set of motor commands (which take no account of the relative direction of the gravitational force) to produce speech-like movements while the body was in three different orientations: upright, prone and supine. The simulations predict a systematic change in jaw pitch angle and horizontal translation resulting from the change in body orientation. Empirical results for five subjects tested under the same conditions as those explored in the simulations are for the most part consistent with the pattern predicted by the model. This suggests that in the case of jaw movements during speech, control signals are not adjusted to account for changes in head and body orientation relative to gravity.

Thesis (M.S.)--University of Michigan, 1984.

Thesis (Ph. D.)--Duke University, 2008. / Includes bibliographical references.