Thesis (M.S.)--University of Michigan, 1976. / Typescript (photocopy). Includes bibliographical references (leaves [66]-73). Also issued in print.

Thesis (M.S.)--University of Michigan, 1976. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [66]-73).

Thesis (M.S.)--University of Michigan, Ann Arbor, 1968. / Typescript (photocopy). Includes bibliographical references (leaves 33-38). Also issued in print.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1968. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 33-38).

There is a dearth of knowledge on the functional organization of the anatomically complex human masseter muscle. Limited physiological studies suggest a functional organization which may differ significantly from human limb muscles. The present studies aimed to examine the putative relationship between structure and function in the human masseter muscle as a basis for understanding function and dysfunction in human jaw muscles. In the first experiment single motor unit (SMU) activity was recorded from pairs of recording sites distributed throughout the masseter muscle. In each case SMU activity at a chosen location was used as a reference to search for synchronized SMU activity at another selected site. The locations of the needle tips were estimated in 3-dimensions (3-D) by means of an optical system, then transferred to 3-D reconstructions derived from Magnetic Resonance images. This approach permitted calculation of the linear distances between verified muscle recording sites. The mean separation of the sites from which synchronous SMU activity could be recorded was 8.8±3.4mm. The putative territories had a preferred orientation in the antero-posterior axis. Motor unit territories were larger than described previously, and appeared to be related to anatomical compartments. The second experiment involved recording activity from stereotactically mapped masseter SMUs. In each case, the lowest sustainable firing frequency (LSFF) was reached by slow increases and decreases in voluntary firing rate, followed by sustained firing at the lowest possible rate. Pulse-discrimination and digital sampling of consecutive inter-spike intervals (ISIs) were then used to measure LSFF for 2-6 separate occlusal and postural tasks to which each unit contributed. There were significant differences between mean ISIs for the tasks performed by most units, which suggests descending drive to masseter units is highly task-dependent. There were also regional differences in unit task specificities. In the third paradigm, reflex SMU activity was recorded from units in the masseter muscle and the inferior head of the lateral pterygoid muscle. Bipolar electrodes fixed to the gingiva near the maxillary canine delivered single pulses of 1ms duration at sub-noxious levels of intensity. At constrained firing frequencies (10, 15Hz), pulses were injected sequentially, with increasing delays, after preselected spikes. More profound inhibition occurred in units firing at 10 than 15Hz. There were significant differences in masseter inhibitory responses when the unit task varied. Reflex inhibition in masseter and lateral pterygoid SMUs is highly frequency-dependent, and also task-dependent in masseter units. The fourth study involved recording activity from SMUs in the masseter muscle. A midline load cell was fixed to the incisor teeth and aligned either perpendicular (P) or 30 degrees anterior (A) to the occlusal plane, without altering jaw position. A rigid spike-triggered averaging (STA) paradigm was used to extract the contribution of individual SMUs to the overall force at load cell orientations P and A. Spikes preceded or followed by an interval of less than 100ms were rejected prior to averaging. At background bite forces from 0.06-8N, the isometric forces apparently developed by individual units varied randomly with load cell orientations, (P range 36.2±19.6mN; A range 38.2±28.4mN). All units could be fired slowly with varying degrees of muscle coactivation, in some instances without contact on the load cell. The use of STA as a method for determining SMU tension in the masseter muscle appears to be task-dependent and in the presence of coactivation may be inappropriate. The findings collectively indicate the heterogeneous nature of SMU behaviour in the human masseter muscle which is consistent with internal muscle compartments based on anatomical features and functional behaviour. There thus appear to be both physiological and anatomical substrates for differential motor control of selected regions of the human masseter muscle. / Dentistry, Faculty of / Graduate

Indiana University-Purdue University Indianapolis (IUPUI) / This study was initiated in order to obtain quantitative information on the possible correlations of incisive biting strength and representative cephalometric measurements as taken from the lateral cephalometric headfilm. It consisted of an examination of 150 subjects and a determination of their incisive biting strength. The results of the study indicate that the five cephalometric measurements chosen were of little predictive value in determining incisal biting force.

A perda dental determina importantes alterações no sistema estomatognático, dentre elas, a redução da performance mastigatória, uma vez que esta é dependente das condições da dentição do indivíduo. Dessa forma, o restabelecimento da função tem grande importância em pacientes reabilitados com próteses bucais. No presente estudo, foram analisados indivíduos adultos reabilitados com diferentes tipos de próteses bucais, com o objetivo de verificar a influência do tipo de reabilitação protética na eficiência dos ciclos mastigatórios por meio da integral da envoltória da atividade eletromiográfica na mastigação habitual de amendoins e uvas passas e na mastigação não-habitual com Parafilme. Participaram desta pesquisa 50 indivíduos divididos em cinco grupos de acordo com o tipo de reabilitação protética. Cada grupo foi constituído por 10 indivíduos: Grupo I portadores de implantes e coroas unitárias; Grupo II portadores de Prótese Total maxilar e Overdenture mandibular sobre implantes; Grupo III portadores de Prótese Total maxilar e mandibular; Grupo IV portadores de Prótese Parcial Removível maxilar e mandibular e Grupo V - indivíduos dentados totais (grupo controle). Neste estudo a eficiência do ciclo mastigatório foi analisada por meio da integral da envoltória do sinal eletromiográfico (microvolts/segundo). Os sinais eletromiográficos foram obtidos na mastigação habitual de amendoins e de uvas passas sem sementes, durante vinte segundos e na mastigação não habitual de Parafilme M® durante dez segundos. Os dados da mastigação foram analisados usando ANOVA e Teste de Duncan (p≤0,05). Os resultados evidenciaram menores valores eletromiográficos para indivíduos dentados totais em todas as condições clínicas avaliadas, seguido do grupo portador de implantes com coroas unitárias. Pode-se concluir que a eficiência dos ciclos mastigatórios foi influenciada pelo tipo de reabilitação protética bucal. / The tooth loss causes important changes in the stomatognathic system, among them the reduction of masticatory performance, since this is dependent on the conditions of a person\'s teeth. Thus, the restoration of function has great importance in patients rehabilitated with oral implants. In this study, we analyzed adult individuals rehabilitated with different types of denture, with the objective of verifying the influence of prosthetic rehabilitation in the efficiency of the cycles by means of the integral of the envelope of EMG activity in the mastication of peanuts and raisins and non-habitual chewing with Parafilm. The sample was 50 individuals, divided into five groups according to the type of prosthetic rehabilitation. Each group comprised 10 individuals: Group I - patients with implants and crowns, Group II - patients with maxillary denture and mandibular overdentures on implants, Group III - patients with maxillary and mandibular denture Group IV - patients with Partial Denture Removable maxillary and mandibular and Group V - dentate subjects (control group). In this study the efficiency of the masticatory cycle was analyzed by the integral of the signal envelope EMG (microvolts / second). The signals were obtained in the mastication of peanuts and raisins without seeds, for twenty seconds and chewing Parafilm unusually for ten seconds. Data of chewing were analyzed using ANOVA and Duncan Test (p≤0.05). The results showed lower EMG values for individuals dentate in all clinical conditions assessed, followed by the group with implants with crowns. It can be concluded that the efficiency of the cycles was influenced by the type of oral prosthetic rehabilitation.

Thesis (doctoral)--Karolinska Institutet, Stockholm, 1985. / Extra title page with thesis statement inserted. Includes bibliographical references.