Bulk Fill flow resin contraction using 3D finite element model and calibration by Fiber Bragg Grating measurement.

Contraction due to polymerization of dental resin can cause failure on the adhesive interfaces, can lead to problems such as the appearance of gaps in the interfaces, postoperative sensitivity, pulp damage and the return of the caries. The objective of this work is the study of stresses on the dental adhesive that are generated by the process shrinkage of resin associated with biting forces. A laboratory experiment measured the strains and temperature inside the FiltekTM Bulk Fill Flow resin during the process of polymerization using Fiber Bragg Grating sensors in an ex vivo tooth. From tomographic images a three-dimensional geometric model of the tooth was reconstructed. A pre-tension was calibrated to simulate the residual contraction on the resin 3 D model. Finally, an Finite Element Method analysis was performed to access the adhesive stresses at the interface enamel/dentin with the adhesive, considering as loading the residual polymerization contraction of the dental resin and also biting loads. The model was able to represented the strain obtained in the laboratory experiment. The results of the stress analysis shows that the outer regions of adhesive are more prone to failure, as veried by dental surgeons in clinical practice.

Avaliação da transmissão de temperatura da resina acrílica para os ossos cortical e medular por meio de redes de Bragg / Evaluation of the temperature transmission of the acrylic resin to the cortical and medullary bones through the Bragg's grating

O objetivo do estudo foi avaliar a alteração de temperatura nos ossos cortical e medular gerados pela resina acrílica na união dos transferentes por meio das redes de Bragg. Foram selecionados dois implantes cone morse Titamax (Neodent) 4 mm x 15 mm. Os implantes foram inseridos em um osso artificial da marca Sawbones, de acordo com as instruções do fabricante, cuja localização dos pilares foi referente aos dentes 44 e 46 com ausência do dente 45. Sobre os implantes foram instalados transferentes para a técnica aberta. Os transferentes foram esplintados por meio de um fio dental e aplicação de resina acrílica pela técnica de Nealon. Foram selecionadas duas resinas acrílicas: Duralay e GC Pattern LS. Dois sensores de fibra ótica foram posicionados, sendo um próximo à região cervical e outro na região apical do implante. Os sensores mensuraram a transferência de calor para o osso cortical e medular com o auxílio de uma pasta térmica (Implastec). Os dados foram submetidos à análise estatística por meio dos testes de normalidade de Shapiro-Wilk, ANOVA a dois critérios e teste de múltiplas comparações post hoc LSD (p<0,05). Foram encontradas diferenças significativas entre Duralay apical eGC Pattern LS cervical, GC Pattern LS cervical eGC Patternapical (p<0,05). As redes de Bragg apresentaram-se sensíveis para a mensuração da transferência de temperatura do transferente para os ossos cortical e medular. A partir dos resultados obtidos, pode-se afirmar que não há risco de necrose óssea (AU).

The purpose of the study was to evaluate the temperature change in the cortical and medullary bones generated by the acrylic resin in the union of transferents through the Bragg's grating. Two cone morse Titamax (Neodent) 4 mm x 15 mm implants were selected. The implants were inserted into a Sawbones artificial bone according to the manufacturer's instructions, abutment location were teeth 44 and 46 with absence of tooth 45. On the implants tranfers were installed for the open technique. The transfers were splined by means of a dental floss and acrylic resin application by the Nealon technique. Two acrylic resins were selected: Duralay and GC Pattern LS. Two fiber optic sensors were positioned, one near the cervical region and other at the implant apical region. The sensors measured the heat transfer to the cortical and medullary bones with the help of a thermal paste (Implastec). Data were submitted to statistical analysis using Shapiro-Wilk normality tests, two way ANOVA, and post hoc LSD multiple comparisons (p <0.05). Significant differences were found between Duralay apical and GC Pattern LS cervical, GC Pattern LS cervical and GC apical Pattern (p <0.05). The Bragg's grating were sensitive to temperature transference measurement from transfers to the cortical and medullary bones. From the results obtained, it is possible to ssure that there is no risk of bone necrosis (AU).

In Vivo Pattern Classification of Ingestive Behavior in Ruminants Using FBG Sensors and Machine Learning.

Pattern classification of ingestive behavior in grazing animals has extreme importance in studies related to animal nutrition, growth and health. In this paper, a system to classify chewing patterns of ruminants in in vivo experiments is developed. The proposal is based on data collected by optical fiber Bragg grating sensors (FBG) that are processed by machine learning techniques. The FBG sensors measure the biomechanical strain during jaw movements, and a decision tree is responsible for the classification of the associated chewing pattern. In this study, patterns associated with food intake of dietary supplement, hay and ryegrass were considered. Additionally, two other important events for ingestive behavior were monitored: rumination and idleness. Experimental results show that the proposed approach for pattern classification is capable of differentiating the five patterns involved in the chewing process with an overall accuracy of 94%.

Análise comparativa em modelo computadorizado bidimensional com simulação do emprego de hastes flexíveis de aço e titânio, na fratura do fêmur da criança, utilizando o método dos elementos finitos / Comparative analysis in a 2D computer model simulating the use of steel and titanium elastic nails in pediatric femur fracture, using the finite element method

OBJETIVO: Apresentar um modelo computadorizado bidimensional, simulando uma fratura do fêmur em criança tratada por hastes flexíveis de aço e titânio, utilizando o método dos elementos finitos, avaliando-se comparativamente o caminho e distribuição das tensões, tensões principais e deformações. MÉTODOS Foram utilizados dois modelos diferentes, gerados pelo aplicativo Ansys®, considerando a simulação de uma fratura transversal na região diafisária, com a espessura de 1mm, cuja estabilização foi feita mediante o emprego de hastes intramedulares de materiais diferentes (aço e titânio), à luz da teoria mecanostática proposta por Frost, em 1987. RESULTADOS: A introdução das hastes intramedulares no fêmur alterou o caminho das tensões, servindo como condutoras das forças compressivas. Na análise comparativa, o modelo com as hastes de titânio, à luz da teoria mecanostática proposta por Frost, apresentou desempenho mais homogêneo quando do estudo das deformações em relação ao modelo com hastes de aço inoxidável. CONCLUSÕES: O modelo proposto atingiu os objetivos de comparar as tensões e deformações entre as simulações das hastes de aço e titânio. Analisando o caminho e distribuição das tensões no modelo (Von Mises e tensões principais), observa-se comportamento biomecânico qualitativamente melhor no modelo com hastes de titânio; todavia, na análise quantitativa, restrita às regiões do foco de fratura, os valores são estatisticamente semelhantes. No estudo das deformações, observa-se comportamento biomecânico mais homogêneo no modelo com hastes de titânio, pois as deformações verificadas nas regiões do foco de fratura apresentam-se dentro das janelas fisiológicas propostas por Frost.

OBJECTIVE: To present a 2D computer model simulating a pediatric femur fracture treated with steel and titanium elastic nails, using the Finite Element Method, with a comparative evaluation of the paths and distribution of stresses, main stresses, and strains. METHODS: Two different models were used, both generated by application Ansys®, considering the simulation of a 1 mm transversal fracture of the diaphysis whose stabilization was performed with the use of intramedullary nails made of different materials (steel and titanium), according to the Mechanostat Theory proposed by Frost in 1987. RESULTS: The introduction of intramedullary nails in the femur has changed the path of stresses, and conducted compressive stresses. In the comparison, the model with titanium nails, according to the Mechanostat Theory proposed by Frost, presented a more homogenous performance in the strain study than the stainless steel nails. CONCLUSIONS: The model proposed attained the objective of comparing stresses and strains between the steel and titanium nails simulations. By analyzing the path and the distribution of stresses in the model (Von Mises and main stresses), one can see the qualitatively improved biomechanical behavior in the titanium nails model, but in the quantitative analysis restricted to the fracture focus regions, the values are statistically similar. In the strain study, the more homogenous biomechanical behavior is seen in the model with titanium nails, as all strains seen in fracture focus regions are within the physiological window proposed by Frost.