The human jaw, like all other articulated body parts, exhibits small oscillatory movements during isometric holding tasks. These movements, known as physiological tremor, arise as a consequence of the interaction of various factors. One of these factors is reflex feedback from peripheral receptors. In the human jaw, receptors that innervate the periodontium are able to transduce minute changes in force. This thesis examines the contribution of these periodontal mechanoreceptors (PMRs) to the genesis of physiological tremor of the human jaw. By using frequency domain analysis of time series recorded during isometric biting tasks, the character of physiological jaw tremor can be revealed. Physiological jaw tremor was observed in force recorded from between the teeth as well as from electromyograms recorded from the principal muscles of mastication. These recordings have shown us that jaw physiological tremor consists of a frequency invariant component between 6 and 10Hz. This frequency remains unaltered under various load conditions where the mechanical resonance of the jaw would be expected to vary greatly (Chapter 2). Such findings indicate a ‘neurogenic’ origin for this tremor. A possible candidate for this neurogenic component of physiological tremor in the jaw is the reflex feedback arising from the PMRs. Using local anaesthetisation, it has been shown in this thesis, that by blocking outflow from the PMRs, the amplitude of neurogenic physiological jaw tremor can be reduced dramatically. This procedure caused a dramatic reduction in not only the mechanical recordings of tremor but also in the coupling between masseteric muscles bilaterally (Chapter 3) and between single motor units recorded from within a homonymous muscle (Chapter 4). The obvious mechanism by which periodontal mechanoreceptor anaesthetisation could reduce the amplitude of physiological tremor in the jaw would be by reducing the amplitude of the oscillatory input to the motoneurones driving the tremor. This interpretation remains controversial however as physiological tremor in the jaw can be observed at force levels above which the PMRs are supposedly saturated in their response. In light of this knowledge, the saturating characteristics of these receptors in terms of reflex output were examined. To do this, a novel stimulation paradigm was devised whereby the incisal teeth were mechanically stimulated with identical stimulus waveforms superimposed upon increasing tooth preloads. This necessitated the use of a frequency response method to quantify the reflexes. An optimal frequency for stimulation was identified and used to confirm that the hyperbolic saturating response of PMRs observed previously, translated to a similar phenomenon in masticatory reflexes (Chapter 5). These data reinforced the idea that physiological tremor in the jaw was not just a consequence of rhythmic reflex input from PMRs, as the dynamic reflex response uncoupled from the input as the receptor-mediated reflex response saturated. An alternative hypothesis was then developed that suggested the effect of PMR suppression in physiological tremor was via tonic rather than rhythmic effects on the masseteric motoneurone pool. By utilising a novel contraction strategy to manipulate the mean firing rate of the motor neuron pool at a given level of force production, data contained in Chapter 6 shows that population motor unit firing statistics influence the expression of physiological tremor, and such manipulations mimic, to an extent, the changes in firing statistics and tremor amplitude seen during anaesthetisation of the PMRs. This thesis therefore posits a mechanism whereby periodontal input influences the firing rate of motoneurones in such a way as to promote tremulous activity (Chapter 5). However, as this proposed mechanism did not explain the full extent of tremor suppression seen during PMR anaesthetisation it can therefore only be considered a contributing factor in a multifactor process. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297555 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2007

This diploma thesis deals with the structural design of the chucking jaws for RUMUL Cracktronic 160 testing machine. This apparatus is used in the fatigue laboratory of Institute of Machine Design FME BUT. Simplification, speed improvement and better test sample griping are expected gains of the new clamping system. Solidworks system is used to create 3D model of the jaws. Stress analysis is created by Finite element method in ANSYS Workbench software.

Os bisfosfonatos são medicamentos amplamente e efetivamente utilizados para o tratamento de doenças osteolíticas. Entretanto, na cavidade oral, é de particular relevância, pois possuem como efeito adverso a osteonecrose dos maxilares induzida pelo uso de bisfosfonatos. Sua etiopatogenia ainda não é bem estabelecida, os métodos de detecção são insatisfatórios e as terapias recomendadas são por vezes, medidas paliativas e ineficazes. Pouco ainda é sabido sobre o efeito do Ácido Zoledrônico na microestrutura óssea, portanto, propusemo-nos a realizar um estudo em modelo animal que analisasse o trabeculado ósseo da mandíbula através da Micro-CT. Foram utilizados 24 ratos machos (Rattus novergicus, albinus, Wistar), com 12 semanas de vida, divididos em 2 grupos: grupo controle (cloreto de sódio 0,9%) e grupo ácido zoledrônico (ácido zoledrônico 0,6mg/kg). As substâncias foram administradas via intraperitoneal a cada 28 dias em um total de 5 doses. Após 150 dias do início do experimento, foi realizada a eutanásia dos animais e então as amostras foram preparadas e escaneadas (Skyscan 1174) para análise da microestrutura óssea através da Micro- CT. O teste t-student demonstrou diferença estatisticamente significativa (p<0,05) em todos os fatores: volume ósseo, densidade óssea, fator de padrão trabecular, índice de modelo estrutural, espessura trabecular, separação trabecular, porosidade total exceção de número de trabéculas e volume tecidual, demonstrando que há alterações significativas na estrutura trabecular pelo uso de bisfosfonatos. O grupo medicado com ácido zoledrônico comparado ao grupo controle demonstrou trabéculas mais espessas, menos separadas e com menores ligações. / Bisphosphonates are widely and effectively drugs used for the treatment of osteolytic disorders. However, in the oral cavity, this situation is of particular relevance as it can lead to bisphosphonate related osteonecrosis of the jaws. Its etiopathogenesis is still not established, detection methods are unsatisfactory and recommended therapies are sometimes palliative and often ineffective. Little is known about the effect of zoledronic acid on the quality of trabecular bone, therefore, we proposed to conduct a study in an animal model to examine the trabecular bone of the jaw through the Micro-CT. 24 male rats were used (Rattus norvegicus, Albinus, Wistar), with 12 weeks old, divided into 2 groups: control group (sodium chloride 0.9%) and group with zoledronic acid (zoledronic acid 0.6 mg / kg). The substances were administered intraperitoneally every 28 days for a total of 5 doses. After 150 days from the beginning of the experiment, the animals were sacrificed and then the samples were prepared and scanned (Skyscan 1174) for analysis of the bone microstructure through Micro-CT. The \"t-student\" test demonstrated statistically significant differences (p<0.05) in all factors: bone volume, osseous density, trabecular pattern, structure model index, trabecular thickness, trabecular separation, total porosity except trabecular number and tissue volume, demonstrating that there are significant changes in the trabecular structure of the bisphosphonates. Zoledronic Acid compared to control group shows thicker, less separate and lower connected trabeculae.

Os bisfosfonatos são medicamentos amplamente e efetivamente utilizados para o tratamento de doenças osteolíticas. Entretanto, na cavidade oral, é de particular relevância, pois possuem como efeito adverso a osteonecrose dos maxilares induzida pelo uso de bisfosfonatos. Sua etiopatogenia ainda não é bem estabelecida, os métodos de detecção são insatisfatórios e as terapias recomendadas são por vezes, medidas paliativas e ineficazes. Pouco ainda é sabido sobre o efeito do Ácido Zoledrônico na microestrutura óssea, portanto, propusemo-nos a realizar um estudo em modelo animal que analisasse o trabeculado ósseo da mandíbula através da Micro-CT. Foram utilizados 24 ratos machos (Rattus novergicus, albinus, Wistar), com 12 semanas de vida, divididos em 2 grupos: grupo controle (cloreto de sódio 0,9%) e grupo ácido zoledrônico (ácido zoledrônico 0,6mg/kg). As substâncias foram administradas via intraperitoneal a cada 28 dias em um total de 5 doses. Após 150 dias do início do experimento, foi realizada a eutanásia dos animais e então as amostras foram preparadas e escaneadas (Skyscan 1174) para análise da microestrutura óssea através da Micro- CT. O teste t-student demonstrou diferença estatisticamente significativa (p<0,05) em todos os fatores: volume ósseo, densidade óssea, fator de padrão trabecular, índice de modelo estrutural, espessura trabecular, separação trabecular, porosidade total exceção de número de trabéculas e volume tecidual, demonstrando que há alterações significativas na estrutura trabecular pelo uso de bisfosfonatos. O grupo medicado com ácido zoledrônico comparado ao grupo controle demonstrou trabéculas mais espessas, menos separadas e com menores ligações. / Bisphosphonates are widely and effectively drugs used for the treatment of osteolytic disorders. However, in the oral cavity, this situation is of particular relevance as it can lead to bisphosphonate related osteonecrosis of the jaws. Its etiopathogenesis is still not established, detection methods are unsatisfactory and recommended therapies are sometimes palliative and often ineffective. Little is known about the effect of zoledronic acid on the quality of trabecular bone, therefore, we proposed to conduct a study in an animal model to examine the trabecular bone of the jaw through the Micro-CT. 24 male rats were used (Rattus norvegicus, Albinus, Wistar), with 12 weeks old, divided into 2 groups: control group (sodium chloride 0.9%) and group with zoledronic acid (zoledronic acid 0.6 mg / kg). The substances were administered intraperitoneally every 28 days for a total of 5 doses. After 150 days from the beginning of the experiment, the animals were sacrificed and then the samples were prepared and scanned (Skyscan 1174) for analysis of the bone microstructure through Micro-CT. The \"t-student\" test demonstrated statistically significant differences (p<0.05) in all factors: bone volume, osseous density, trabecular pattern, structure model index, trabecular thickness, trabecular separation, total porosity except trabecular number and tissue volume, demonstrating that there are significant changes in the trabecular structure of the bisphosphonates. Zoledronic Acid compared to control group shows thicker, less separate and lower connected trabeculae.

The aim of this thesis is the design of laboratory crusher of mineral raw materials. This work is focused on the research of possible types of machinery for crushing process, list of shredders available at domestic and foreign markets, selection of the principle of diminution of mineral resources, the choice of approach, suggestion of calculation of the chosen design, creating a 3D model and drawings, making the strength analysis for selected parts, risk analysis.