Abstract Introduction The term cracked tooth syndrome refers to an incomplete fracture of a vital posterior tooth that involves the dentin and occasionally extends into the pulp. There is a very limited number of publications trying to model dentin crack growth using numerical techniques. Therefore, it is essential to numerically model this phenomenon in order to improve the clinical procedures. Methods A 2D finite element model is proposed to simulate crack initiation and propagation in a restored premolar tooth. The geometric model was based on computed tomography data. A special finite element technique, named mesh fragmentation technique, is used to model and analyze the behavior of the tooth. This technique was used to model cracks in quasi-brittle materials based on the use of interface solid finite elements with high aspects ratio. A tension damage constitutive relation between stresses and strains consistent with the continuous strong discontinuity approach is used to describe crack formation and propagation. Results The main aspects of modeling technique and procedures are explained in detail as well as the whole results, including both elastic and fracture analyses of the restored tooth. Conclusion The results of the current fracture analysis show that, under various loading conditions, there is no crack initiation in the restored tooth under typical loading magnitude. However, in the case of tooth with a pre-existing crack, which can be aroused during the restoration process, a crack propagation was observed, while they did not reach a critical fracture state.

RESUMO Objetivo: analisar a força axial da língua e parâmetros relacionados por meio do FORLING. Método: foram analisados os dados de 92 participantes, entre homens e mulheres, com média de 23,3±7,7 anos. Resultados: no parâmetro força média da língua, identificaram-se valores médios de 13,0 N, já para a força máxima observou-se valor médio de 18,3 N. A força média e a máxima da língua apresentaram correlação positiva e associação altamente significante (p<0,001). A energia acumulada pela língua indicou valores de 131,1 N/s. O tempo médio gasto para que se alcance a força máxima da língua foi de 3,8 segundos, indicando um efeito do treinamento ao se comparar a 1ª à 3ª medida, com redução dos valores (p<0,001). Conclusão: o instrumento demonstrou ser capaz de mensurar parâmetros importantes para o fonoaudiólogo, indicando ser uma promissora ferramenta complementar à avaliação clínica fonoaudiológica.

ABSTRACT Purpose: to analyze axial tongue strength and related parameters by using the Forling. Methods: data regarding 92 participants, including men and women with a mean age of 23.3 ± 7.7 years, were analyzed. Results: the mean value of the mean tongue strength was 13.0 N, and the maximum strength value was 18.3 N. The mean and maximum tongue strengths showed positive correlation and highly significant association (p < 0.001). The energy accumulated by the tongue was 131.1 N/s. The mean time required for the maximum tongue strength to be reached was 3.8 s, and the decrease in time (p < 0.001) from the first to the third measurements indicates an effect of training. Conclusion: the instrument proved to be capable of measuring parameters that are important to the speech-language pathologist, indicating that it can be a promising complementary tool for clinical evaluation.

Introduction : This study aims to evaluate the influence of the biomechanical behavior of the midpalatal suture (MPS) during the rapid maxillary expansion (RME) when modeled by the Finite Element Method. Methods Four simulation alternatives are discussed and, for each analysis, the suture is considered as a functional unit with a different mechanical behavior: (i) without MPS elements, (ii) MPS with Young's modulus (E) equal to 1 MPa, (ii) MPS with E equal to 0.01 MPa and (iv) MPS with bilinear elastic behavior. Results The stress analysis showed that, when MPS is not considered in the model, stress peaks are reduced in magnitude and their distribution is restricted to a smaller area when compared to the model with the inclusion of MPS (E=1 MPa). The increased suture stiffness also has a direct influence on MPS displacements after 30 expander activations. Conclusion The consideration of the MPS in RME computer models influences greatly the calculated displacements between the suture bone ends, even as the stress levels in maxillary structures. Furthermore, as proposed for the described model, the elastic bilinear behavior assigned to MPS allows coherent prediction of stresses and displacements results, being a good representation for this suture overall behavior.

INTRODUCTION: This paper aims to describe a model to simulate otosclerosis using a mass-spring model and to correlate the results with the clinical and audiological data on the disease. METHODS: A mass-spring model was used to represent the behavior of the auditory system simulating otosclerosis. The model consisted of six masses (air volume in the external auditory canal; tympanic membrane; malleus; incus; stapes, and cochlear fluid), springs and dashpots simulating the supporting ligaments and muscles. The parameters to simulate the disease were obtained from the literature; stapedial annular ligament stiffness was increased by 10-fold and to 100-fold and stapes mass increased by 5-fold. RESULTS: There was a decrease in stapes displacement in the lower frequencies when the stiffness of the stapedial annular ligament was increased. It was also found a reduction in stapes displacement in the higher frequencies with increased stapes mass. CONCLUSION:The increased stiffness of the stapedial annular ligament can be an indication of early stage disease, whereas increased bone growth suggests disease progression. The results of the simulation are in agreement with the clinical and audiological disease and support the need for further study of the stapedial annular ligament to find ways to evaluate its functioning and thus enable early detection of hearing losses caused by changes in that structure.

Por muitos anos, pesquisadores têm procurado métodos para quantificar a força da língua e muitos instrumentos foram construídos para este fim. O objetivo deste trabalho é apresentar uma revisão crítica da literatura sobre instrumentos para quantificar a força de língua. Os 30 aparelhos encontrados foram agrupados em quatro diferentes categorias: bocal contendo sensores (n=9), sensores fixados nos dentes, palato ou em placas palatais (n=8), bulbos preenchidos com fluidos e conectados a sensores de pressão (n=7) e outras tecnologias (n=8). Esses instrumentos podem, potencialmente, auxiliar o fonoaudiólogo na avaliação miofuncional orofacial, fazendo com que o diagnóstico de força da língua seja mais preciso. Alguns aparelhos apresentam desvantagens, tais como não serem sensíveis a pequenas mudanças de força, dificuldades na reprodutibilidade do posicionamento e outros pontos específicos. A grande variação de valores de força/pressão máxima e média encontrados relaciona-se à grande diversidade dos métodos, que empregam diferentes tecnologias.

For several years, researchers have been looking for methods to quantify tongue force and a lot of devices were constructed for this purpose. The purpose of this study is to present a critical literature review about the devices to quantify tongue strength. Thirty devices were found. They were grouped into four different categories: mouthpiece containing sensors (n=9), sensors attached on teeth surface or on palatal plates (n=8), bulbs filled with some fluid and connected to a pressure sensor (n=7) and other technologies (n=8). These methods can, potentially, help speech-language pathologists in the orofacial myology evaluation, making the diagnosis of tongue force more reliable. Some of them present disadvantages such as not being sensitive enough to small changes in force, difficulties in positioning reproducibility and other specific points. The large variation in maximum and average strength/pressure values are related to the large diversity of the methods, which use different technologies.

OBJECTIVE: The occlusal patterns are key requirements for the clinical success of oral rehabilitation supported by implants. This study compared the stresses generated by the disocclusion in the canine guide occlusion (CGO) and bilateral balanced occlusion (BBO) on the implants and metallic infrastructure of a complete Brånemark protocol-type denture modified with the inclusion of one posterior short implant on each side. MATERIAL AND METHODS: A three-dimensional model simulated a mandible with seven titanium implants as pillars, five of them installed between the mental foramen and the two posterior implants, located at the midpoint of the occlusal surface of the first molar. A load of 15 N with an angle of 45° was applied to a tooth or distributed across three teeth to simulate the CGO or BBO, respectively. The commercial program ABAQUS® was used for the model development, before and after the processing of the data. The results were based on a linear static analysis and were used to compare the magnitude of the equivalent stress for each of the simulations. RESULTS: The results showed that the disocclusion in CGO generated higher stresses concentrated on the working side in the region of the short implant. In BBO, the stresses were less intense and more evenly distributed on the prosthesis. The maximum stress found in the simulation of the disocclusion in CGO was two times higher than that found in the simulation of the BBO. The point of maximum stress was located in the neck of the short implant on the working side. CONCLUSIONS: Under the conditions of this study, it was concluded that the BBO pattern was more suitable than CGO for the lower complete denture supported by implants without free distal ends.

OBJETIVO: Analisar a influência de peso, altura e índice de massa corporal na força axial da língua. MÉTODOS: Foram analisados os prontuários referentes a 44 indivíduos com idade entre 20 e 37 anos, sendo 11 (25%) homens e 33 (75%) mulheres. Foram pesquisadas as informações referentes a peso, altura, resultado da avaliação clínica da língua (tônus lingual) e resultado da avaliação instrumental da força axial da língua, sendo esta última realizada por meio do FORLING. Os dados foram analisados estatisticamente. RESULTADOS: Não foram observadas diferenças entre os valores de força em relação às variáveis de classificação do índice de massa corporal e avaliação clínica da língua. O índice de massa corporal e o peso apresentaram correlação positiva com a força média da língua. Verificou-se, ainda, correlação positiva forte entre as variáveis de força média, força máxima e maior força máxima da língua. CONCLUSÃO: Embora o índice de massa corporal e o peso se correlacionem de forma positiva com a força média axial da língua, não há associação entre a classificação do índice de massa corporal e as forças axiais da língua.

PURPOSE: To analyze the influence of weight, height and body mass index in the axial tongue force. METHODS: Medical records with data from 44 subjects aged between 20 and 37 years, 11 (25%) males and 33 (75%) female, were analyzed. The investigated information were weight, height, result of clinical evaluation for tongue force (lingual tonus) and instrumental assessment of axial tongue force, which was accomplished by using the FORLING. Data was statistically analyzed. RESULTS: No differences were observed between the force values regarding the variables body mass index classification and clinical classification of tongue force. Body mass index and weight had positive correlation with mean tongue force. There was a strong positive correlation between the variables mean force, maximum force and highest maximum force. CONCLUSION: Although body mass index and weight correlated positively with the mean axial tongue force, there was no association between body mass index classification and the axial tongue forces.

O desenvolvimento de novos aparatos usando materiais disponíveis e de baixo custo pode ser uma alternativa viável para o tratamento cirúrgico de fraturas em ossos longos de bovinos. O objetivo deste estudo foi avaliar a resistência mecânica de fêmures de bovinos jovens com fratura diafiseal, imobilizados com hastes intramedulares bloqueadas, compostas por diferentes polímeros. Para tanto, testes físicos de compressão e flexão, por meio de uma máquina universal de ensaios foram realizados em quatro grupos distintos de seis fêmures obtidos de bovinos jovens. Em um dos grupos, os ossos foram mantidos íntegros (grupo controle), enquanto que os outros os ossos, foram fraturados e imobilizados com uma haste intramedular bloqueada, composta por polipropileno, poliacetal ou poliamida (uma para cada grupo). Independente do polímero utilizado, nenhuma das hastes estudadas ofereceu aos fêmures fraturados resistência comparável ao osso íntegro, quando consideradas em conjunto as forças de flexão e compressão. A concordância desses achados com resultados in vivo previamente publicados, demonstra que a metodologia utilizada para testes ex vivo pode ser útil na seleção de materiais mais resistentes para confecção de novos modelos.

The development of new devices using available and low cost materials may be an useful alternative for the treatment of long bone fractures in large animals. The aim of this study was to evaluate the mechanical strength of young bovine femur with diaphyseal fracture fixed with different polymeric intramedullary nails. Bending and compression tests using a universal machine were carried out in 4 distinct groups of 6 femurs from young calves. In one of the groups bones were intact while in the other three fractured bones were fixed using an intramedullary nail made of polypropylene, polyacetal or polyamide (one for each group). Considering bending and compression tests together, none of the used polymers offered strength to the fractured bones similar to the intact ones. The agreement of this findings with those from previous published in vivo results indicates that the employed ex vivo methods for mechanical assays may be useful in the search of stronger materials to be used in development of new devices.

O presente trabalho apresenta o desenvolvimento de um sistema para medição da força axial da língua humana. Como diferencial, o protótipo desenvolvido apresenta concordância metodológica com a prática clínica fonoaudiológica, no que diz respeito ao teste aplicado para a percepção da tensão lingual. O trabalho também verifica quais os pontos notáveis de força devem ser utilizados como parâmetros para a análise clínica, justificados a partir de testes de reprodutibilidade e repetitividade, numa tentativa de selecionar quais desses pontos podem ser empregados como parâmetros para o diagnóstico e como indicadores do sucesso de terapias. Resultados preliminares apontam para o uso da força média como medida mais confiável para a clínica fonaudiológica.

This work presents the development of a system for the measurement of the axial forces produced by the human tongue. A prototype was developed which reproduces the underlying principles of the methods normally adopted in clinical procedures, with the advantage that it allows the phonoaudiologist to obtain objective measurements of these forces. This work also presents an analysis based on the repeatability and the reproducibility of the forces in an attempt to select which of these forces can be employed as parameters for diagnosis and as success indicators of therapies. Preliminary results indicate the mean force as the most reliable parameter.

Oral forces applied to human teeth during biting and mastication are normally described in the literature only in terms of their axial components. The purpose of this study was to fully determine the spatial characteristics of the oral resultant force - its normal and tangential components - for a given individual. A load cell was especially manufactured to measure oral force and was temporarily implanted as a prosthetic device in the dental arch of a volunteer, replacing his missing upper first molar. The mastication and occlusion tests were carried out in such a way the cell should withstand the loads applied to the molar, and its state of strain was recorded by strain gauges attached to it. Based on the results of these tests and using balance equations, normal and tangential components of the resultant oral force were determined. For direct occlusion, without interposition any obstacle between cusps, a peak normal force of 135 N was recorded simultaneously to a tangential force of 44 N. For mastication of biscuits, a peak normal force of 133 N and a tangential force of 39 N were obtained.