Avaliação das propriedades de superfície, mecânicas e ópticas de resinas acrílicas de base de dentadura confeccionadas pelo método CAD-CAM com processo de envelhecimento e imersão em bebidas corantes / Evaluation of surface, mechanical and optical properties of denture base acrylic resins made by the CAD-CAM method with aging process and immersion in coloring drinks

O objetivo desse estudo foi investigar as propriedades de superfície, estabilidade de cor e propriedades mecânicas de resinas acrílicas para base de dentadura do método convencional, processada por micro-ondas, fresada e impressa 3D diante de diferentes tempos de envelhecimento e imersão em bebidas corantes. Além disso, realizar uma revisão sistemática para avaliar e comparar, através de estudos de ensaios clínicos, próteses totais fabricadas pelo método CAD/CAM com fabricadas convencionalmente, em termos de tempo clínico, manutenção, retenção, estabilidade, eficácia mastigatória, satisfação e qualidade de vida. Um total de 480 amostras redondas (10 × 3,3 ± 0,03 mm) foram confeccionadas para avaliação das propriedades de superfície e estabilidade de cor, divididas entre os quatro grupos principais de resinas e subdivididas em quatro tempos de análise (T0, T1, T2 e T3) e bebidas corantes (água, café, vinho e refrigerante cola), resultando um n = 10 para cada subgrupo. Um total de 160 amostras retangulares (64 × 10 × 3,3 ± 0,03 mm) foram confeccionadas para avaliação das propriedades mecânicas, divididas entre os quatro grupos principais de resinas e subdivididas em quatro tempos de análise (T0, T1, T2 e T3), resultando um n = 10 para cada subgrupo. A revisão sistemática seguiu os Itens de Relatório Preferenciais para Revisões Sistemáticas e Meta-Análises (PRISMA) e foi registrada no Registro Prospectivo Internacional de Revisões Sistemáticas (PROSPERO) (CRD42022296907). A busca eletrônica foi realizada nas bases de dados PubMed/MEDLINE, Web of Science e Scopus até dezembro de 2021. A questão formulada para população, intervenção, comparação e resultado (PICO) foi "Pacientes reabilitados com próteses totais com tecnologia CAD/CAM apresentam parâmetros clínicos semelhantes aos pacientes reabilitados com próteses totais convencionais?". A resina fresada apresentou os melhores resultados das propriedades de superfície diante do efeito do envelhecimento, enquanto que a resina impressa 3D apresentou resultados semelhantes as resinas tradicionais. A resina de Impressão 3D apresentou não ter propriedades ópticas adequadas diante do efeito do envelhecimento, enquanto que a resina fresada apresentou as melhores propriedades. As bebidas corantes não alteraram as propriedades de superfície das resinas, entretanto afetaram suas propriedades ópticas, principalmente a resina de impressão 3D e a processada por micro-ondas. A resina de dentadura fresada CAD/CAM apresentou propriedades mecânicas semelhantes as resinas tradicionais, enquanto que a impressa 3D não apresentou propriedades mecânicas adequadas para uso clínico à longo prazo. As próteses do método de fresagem apresentaram melhor desempenho clínico que as próteses convencionais, em termos de qualidade de vida, satisfação, retenção, estabilidade, tempo clínico e custo, enquanto que as de impressão 3D não apresentaram diferenças. Ambos os métodos do CAD/CAM apresentaram não haver diferenças da eficácia mastigatória em relação as próteses convencionais(AU)

The objective of this study was to investigate the surface properties, color stability and mechanical properties of acrylic resins for denture base of the conventional method, processed by microwave, milled and 3D printed in face of different aging times and immersion in coloring drinks. In addition, carry out a systematic review to evaluate and compare, through clinical trial studies, complete dentures manufactured by the CAD/CAM method with those manufactured conventionally, in terms of clinical time, maintenance, retention, stability, masticatory efficiency, satisfaction and quality of life. A total of 480 round samples (10 × 3.3 ± 0.03 mm) were made to evaluate surface properties and color stability, divided among the four main groups of resins and subdivided into four analysis times (T0, T1, T2 and T3) and coloring drinks (water, coffee, wine and cola), resulting in n = 10 for each subgroup. A total of 160 rectangular samples (64 × 10 × 3.3 ± 0.03 mm) were prepared to evaluate the mechanical properties, divided among the four main groups of resins and subdivided into four analysis times (T0, T1, T2 and T3), resulting in n = 10 for each subgroup. The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Registry of Systematic Reviews (PROSPERO) (CRD42022296907). The electronic search was performed in the PubMed/MEDLINE, Web of Science and Scopus databases until December 2021. The question formulated for population, intervention, comparison and result (PICO) was "Patients rehabilitated with complete dentures with CAD/CAM technology present clinical parameters similar to patients rehabilitated with conventional complete dentures?". The milled resin presented the best results of surface properties in the face of aging effect, while the 3D printed resin presented similar results to traditional resins. The 3D Printing resin did not have adequate optical properties due to the aging effect, while the milled resin showed the best properties. Coloring drinks do not change the surface properties of resins, but optical printing solutions, mainly 3D printing resin and microwave-processed resin. The CAD/CAM milled denture resin presented mechanical properties similar to traditional resins, while the 3D printed denture resin did not present adequate mechanical properties for long-term clinical use. The milling method prostheses showed better clinical performance than conventional prostheses, in terms of quality of life, satisfaction, retention, stability, clinical time and cost, while the 3D printing prostheses showed no differences. Both CAD/CAM methods showed no differences in masticatory efficiency in relation to conventional prostheses(AU)

Biomechanical Study of New Biodegradable Esophageal Stent / 中国医疗器械杂志

The radial force of the degradable esophageal stent before and after degradation is one of the important indicators for effective treatment of esophageal stricture. Based on a combination of in vitro experiments and finite element analysis, this paper studies and verifies the biomechanical properties of a new type of degradable esophageal stent under different esophageal stricture conditions. Under radial extrusion conditions, the maximum stress at the port of the stent is 65.25 MPa, and the maximum strain is 1.98%; The peak values of stress and strain under local extrusion and plane extrusion conditions both appear in the extrusion area and the compression expansion area at both ends, which are respectively 48.68 MPa, 46.40 MPa, 0.49%, 1.13%. The maximum radial force of the undegraded stent was 11.22 N, and 97% and 51% of the maximum radial force were maintained after 3 months and 6 months of degradation, respectively. The research results verify the safety and effectiveness of the radial force of the new degradable esophageal stent, and provide a theoretical basis for the clinical treatment of esophageal stricture.

Research on real-time detection system of catheter delivering force in vascular interventional robots / 生物医学工程学杂志

In existing vascular interventional surgical robots, it is difficult to accurately detect the delivery force of the catheter/guidewire at the slave side. Aiming to solve this problem, a real-time force detection system was designed for vascular interventional surgical (VIS) robots based on catheter push force. Firstly, the transfer process of catheter operating forces in the slave end of the interventional robot was analyzed and modeled, and the design principle of the catheter operating force detection system was obtained. Secondly, based on the principle of stress and strain, a torque sensor was designed and integrated into the internal transmission shaft of the slave end of the interventional robot, and a data acquisition and processing system was established. Thirdly, an ATI high-precision torque sensor was used to build the experimental platform, and the designed sensor was tested and calibrated. Finally, sensor test experiments under ideal static/dynamic conditions and simulated catheter delivery tests based on actual human computed tomography (CT) data and vascular model were carried out. The results showed that the average relative detection error of the designed sensor system was 1.26% under ideal static conditions and 1.38% under ideal dynamic stability conditions. The system can detect on-line catheter operation force at high precision, which is of great significance towards improving patient safety in interventional robotic surgery.

Attractiveness of the facial profile: comparison of Class II patients treated with Twin Force® or intermaxillary elastics

ABSTRACT Objective: To compare the facial profile attractiveness of Class II patients treated with Twin Force® or intermaxillary elastics. Methods: Sample comprised 47 Class II patients divided into two groups: G1) TWIN FORCE - 25 patients treated with fixed appliances and Twin Force® fixed functional appliance (mean initial age was 17.91 ± 7.13 years, mean final age was 20.45 ± 7.18 years, and mean treatment time was 2.53 ± 0.83 years); G2) ELASTICS - 22 patients treated with fixed appliances and Class II intermaxillary elastics (mean initial age was 15.87 ± 5.64 years, mean final age was 18.63 ± 5.79 years and mean treatment time was 2.75 ± 0.60 years). Lateral cephalograms from pretreatment and posttreatment were used. Cephalometric variables were measured and silhouettes of facial profile were constructed and evaluated by 48 laypeople and 63 orthodontists, rating the attractiveness from 0 (most unattractive profile) to 10 (most attractive profile). Intergroup comparisons were performed with Mann-Whitney and independent t-tests. Results: At pretreatment, facial profile of the Twin Force® group was less attractive than the Elastics group. Treatment with Twin Force® or Class II elastics resulted in similar facial profile attractiveness, but the facial convexity was more reduced in the Twin Force® group. Orthodontists were more critical than laypeople. Conclusions: Treatment with Twin Force® or Class II elastics produced similar facial profile attractiveness at posttreatment. Profile attractiveness was reduced with treatment in the elastic group, and improved in the Twin Force® group. Facial convexity was more reduced with treatment in the Twin Force® group.

RESUMO Objetivo: Comparar a atratividade do perfil facial em pacientes Classe II tratados com Twin Force® ou elásticos intermaxilares. Métodos: A amostra foi composta por 47 pacientes Classe II divididos em dois grupos: G1 - Twin Force® (25 pacientes tratados com aparelhos fixos e o aparelho funcional Twin Force®; idade inicial média de 17,91 ± 7,13 anos, idade final média de 20,45 ± 7,18 anos, e tempo médio de tratamento de 2,53 ± 0,83 anos); G2 - Elásticos (22 pacientes tratados com aparelhos fixos e elásticos intermaxilares de Classe II, idade inicial média de 15,87 ± 5,64 anos, idade final média de 18,63 ± 5,79 anos, e tempo médio de tratamento de 2,75 ± 0,60 anos). Foram usadas telerradiografias laterais pré- e pós-tratamento. As variáveis cefalométricas foram mensuradas, e silhuetas do perfil facial foram construídas e avaliadas por 48 leigos e 63 ortodontistas, que pontuaram a atratividade entre 0 (perfil menos atraente) e 10 (perfil mais atraente). As comparações intergrupos foram realizadas com os testes Mann-Whitney e t de Student para amostras independentes. Resultados: Na fase pré-tratamento, o perfil facial no grupo Twin Force® foi menos atrativo do que no grupo Elásticos. Os tratamentos com o Twin Force® ou com Elásticos de Classe II resultaram em atratividade semelhante do perfil facial, mas a convexidade facial foi mais reduzida no grupo Twin Force®. Os ortodontistas foram mais críticos do que os leigos. Conclusões: Apesar de os tratamentos com o Twin Force® ou com Elásticos de Classe II terem resultado em atratividade semelhante do perfil facial após o tratamento, a atratividade do perfil foi reduzida com o tratamento no grupo Elásticos e melhorou no grupo Twin Force®. A convexidade facial foi mais reduzida com o tratamento no grupo Twin Force®.

Influence of bone defect position and span in 3-point bending tests: experimental and finite element analysis

Abstract: Three-point bending test is the most common mechanical test used for quantifying the biomechanical quality of bone tissue and bone healing in small animals. However, there is a lack of standardization for evaluation of bone repair by cortical perforation. The aim of this study was to determine the influence of bone defect position in the proximal metaphysis of rat tibias during load application and different span configuration on the three-point bending test outcomes. Cortical defects with 1.6 mm diameter were created at a standardized location on the medial surface of 60 tibias of male Wistar rats. The animals were euthanized 7 days after surgery. Five specimens were used to create 3D models for finite element analysis using high-resolution micro-CT images. Two spans (6 and 10mm) and three positions of the bone defect in relation to the load application (upward, frontal and downward) were evaluated experimentally (n = 10) and in finite element analysis (n = 5). Maximum load (N) and stiffness (N/mm) were statistically analyzed with 2-way ANOVA and Tukey test (α = 0.05). The results demonstrated that span and orientation of the bone defect significantly influenced the fracture pattern, stress distribution and force versus displacement relation. Therefore, reliable outcome can be achieved creating the bone defect at 8 mm from the extremity of the proximal epiphysis; placing a 10 mm distance span and downward facing defect position to allow a better distribution of stress and more fracture patterns that reached the bone defect target area with less intra-group variability.

Comparative study on the mechanical properties of lower limb arterial stents under various deformation modes / 生物医学工程学杂志

Lower extremity movement is a complex and large range of limb movement. Arterial stents implanted in lower extremity are prone to complex mechanical deformation, so the stent is required to have high comprehensive mechanical properties. In order to evaluate the mechanical property of different stents, in this paper, finite element method was used to simulate and compare the mechanical properties of six nitinol stents (Absolute Pro, Complete SE, Lifestent, Protégé EverFlex, Pulsar-35 and New) under different deformation modes, such as radial compression, axial compression/tension, bending and torsion, and the radial support performance of the stents was verified by experiments. The results showed that the comprehensive performance of New stent was better than other stents. Among which the radial support performance was higher than Absolute Pro and Pulsar-35 stent, the axial support performance was better than Complete SE, Lifestent and Protégé EverFlex stent, the flexibility was superior to Protégé Everflex stent, and the torsion performance was better than Complete SE, Lifestent and Protégé Everflex stent. The TTR2 type radial support force tester was used to test the radial support performance of 6 types, and the finite element analysis results were verified. The mechanical properties of the stent are closely related to the structural size. The result provides a reference for choosing a suitable stent according to the needs of the diseased location in clinical applications.

O trabalho mecânico segmentar como novo instrumento de avaliação do controle postural / The segmentary mechanical work as a new instrument to postural control evaluation

Objetivo: Calcular o trabalho mecânico (W), aplicando o trabalho mecânico total (Wtot) e o trabalho segmentar (Wseg) como um novo recurso de avaliação complementar dos mecanismos de controle postural em sujeitos submetidos a perturbação motora e visual. Método: Dez voluntários adultos saudáveis do sexo masculino foram selecionados com idade 25,6 (± 2,26) anos, cuja altura era de 1,69 (± 0,25) m e peso corporal de 68,22 (± 0,25) kg. Os dados cinemáticos da extensão do tronco com os olhos abertos e vendados foram capturados com frequência de 200 Hz. Dessa forma, foi selecionado o intervalo pós-perturbação e o Wseg (tronco, cabeça, etc) e o trabalho mecânico total (Wtot) calculados, que foram obtidos por meio de energia mecânica total integral. Resultados: A análise estatística das informações foi feita pelo teste t student para dados emparelhados. Não houve diferença significativa (p<0,08) para a Wtot durante o intervalo pós-perturbação. Por outro lado, houve uma diferença significativa (p<0,05) no intervalo pós-perturbação de Wseg. Entretanto, houve diferenças significativas no intervalo (p<0,05). Esta diferença está relacionada com Wseg de cabeça (Wcabeça) e membros inferiores (Wperna e Wcoxa ) no intervalo pós-perturbação com intervalo inicial de [0. 60] ms e [0. 100] ms após a auto-perturbação. Conclusão: Essas diferenças encontradas em Wcabeça entre as duas condições podem estar associadas a modulações do sistema vestibulo-ocular-motor. Por outro lado, as diferenças encontradas em Wperna e Wcoxa podem ser associadas a mecanismos de ajuste somato-sensorial.

Objectie: Calculate the mechanical work (W), applying the total mechanical work (Wtot) and segmental work (Wseg) as a new complementary evaluation resource of the postural control mechanisms in subjects undergoing motor and visual disturbance. Methods: Ten healthy adult male volunteers were selected with ages 25.6 (±2.26) years, whose height was 1.69 (± 0.25) m and body weight was 68.22 (± 0.25) kg. Kinematic data of trunk extension with eyes open and blindfolded were captured with a frequency of 200 Hz. This way the post perturbation interval has been selected and the Wseg (i.e. trunk, head, etc) and the total mechanical work (Wtot) calculated, which were obtained by means of total integral mechanical energy. Results: The statistical analyzing of information was done by paired-data Student's t test. There has been no significant difference (p<0,08) for the Wtot during the post perturbation interval. On the other hand, there has been a significant difference (p<0.05) in the post perturbation interval of Wseg. However, there were significant differences in interval (p<0.05). This difference is related to Wseg of head (Whead) and lower limbs (Wleg and Wthigh ) in the post-perturbation interval with early range of [0. 60] ms and [0. 100] ms after the self-perturbation. Conclusion: These differences that were found in Whead between the two conditions can be associated with modulations of the vestibulo-ocular-motor system. On the other hand, the differences that were found in Wleg and Wthigh can be associated with somato-sensory adjustment mechanisms.

Physicomechanical properties of different nanohybrid composites after aging: color stability, flexural strength, and microhardness

Aim: To evaluate the physicomechanical properties of different hybrid composites (Charisma Diamond - CD, Aura - AU, NT Premium - NT, Opallis - OP, Filtek Z250 ­ Z250) after 6 months of aging in distilled water. Methods: Discs were fabricated and color measurements were performed after 24 hours and at 7, 30, and 180 days. Flexural strength was determined using the three-point bending test. For the microhardness test, the specimens were flattened to obtain polished and flat surfaces and indentations. The results for ∆E and microhardness were analyzed by two-way repeated-measures ANOVA and Tukey's HSD test. The flexural strength results were analyzed by two-way ANOVA and Tukey's test (α=0.05). Results: The ∆E values for composite resins varied in the following order: CD (3.54)a < Z250 (4.70)ab < AU (4.95)ab < OP (5.20)ab < NT (6.23)b. ∆E values were lower for 24 h (3.84)a < 7 days (4.43)ab < 30 days (4.93)b. The highest values were observed after 180 days (ΔE = 6.54)c. The flexural strength of composite resins varied in the following order: CD (89.17 MPa)a < Z250 (73.06 MPa)b < OP (60.30 MPa)c < NT (51.28 MPa)c < AU (23.77 MPa)d. Flexural strength values were significantly higher for 24 h (68.62 MPa)a < 180 days (51.40 MPa)b. The microhardness of composite resins varied in the following order: Z250 (112.05)a < CD (102.15)ab < OP (92.04)bc < NT (87.77)d < AU (87.68)d. Microhardness was significantly higher for 180 days (113.44)a < 24 h (78.21)b. Conclusion: The microhybrid (Z250) and one of the nanohybrid composites (CD) performed better. The color stability and flexural strength of all tested composites decreased with storage time

In vitro experimental study on the mechanical properties of biodegradable polymer stents / 生物医学工程学杂志

experimental test for mechanical properties of a vascular stent is a main method to evaluate its effectiveness and safety, which is of great significance to the clinical applications. In this study, a comparative study of planar, V-groove and radial compression methods for the radial support property test were performed, and the effects of compression rate and circumferential position on the test results were conducted. Based on the three-point bending method, the influences of compression rate and circumferential position on flexibility were also explored. And then a best test proposal was selected to evaluate the radial support property and flexibility of the three self-designed stents and the comparative biodegradable vascular stent (BVS) (BVS1.1, Abbott Vascular, USA) with different outside diameters of 1.4 mm, 1.7 mm and 2.4 mm. The results show that the developing trends of the compression load with the compression displacement measured by the three radial support property test methods are the same, but normalized radial force values are quite different. The planar compression method is more suitable for comparing the radial support properties of stents with different diameters and structures. Compression rate has no obvious effect on the testing results of both the radial support property and flexibility. Compression circumferential position has a great impact on testing radial support property with the planar or V-groove compression methods and testing flexibility with three-point bending method. The radial support properties of all the three self-designed stents are improved at a certain degree compared to that of the BVS stent. The study has better guide significance and reference value for testing mechanical properties of vascular stents.

Real-time measurement of cell contractile force during activation of human hepatic stellate cell line LX-2 / 生物医学工程学杂志

The contractile force of hepatic stellate cells plays a very important role in liver damage, hepatitis and fibrosis. In this paper, a method based on polydimethylsiloxane (PDMS) thin micropillar arrays is proposed to measure the contractile force of human hepatic stellate cell line LX-2, which enables dynamic measurement of the subcellular distribution of force magnitude and direction. First, thin micropillar arrays on glass bottom dish were fabricated using two-step casting process in order to meet the working distance requirement of 100× objective lens. After hydrophilic treatment and protein imprint, cells were seeded on the micropillar arrays. LX-2 cells, which were quiesced by growth in serum-free medium, were activated by adding fetal bovine serum (FBS). The deflections of the micropillars were achieved by image processing technique, and then the contractile force of cells exerted on the micropillars was calculated according to mechanical simulation results, and was analyzed under both quiescent and activated conditions. The experimental results show that the average traction force of quiescent cells is about 20 nN, while the contractile force of activated cells increased to 110 nN upon adding FBS. This method can quantify the contractile force of LX-2 cell on subcellular scale in both quiescent and activated states, which may benefit pathology study and drug screen for chronic liver diseases resulted from liver fibrosis.

Introduction of EOS imaging system and its current research status in evaluating clinical value of lower limb force line / 中国骨伤

The principle and technical background of EOS imaging system are introduced. Combining with the publicity of this technology and the existing literature reports, it is known that low dose EOS technology can reduce radiation dose by 5 to 10 times in the course of examination, and micro dose EOS can even reduce radiation dose by 45 times. The image quality is only high or low; the system has EOS 2D and 3D workstations, which can help clinicians to measure and evaluate coronal and sagittal force lines of lower limbs easily. The tilt and torsion of limbs can be measured three-dimensional after three-dimensional model reconstruction in the three-dimensional workstation. Using these results, preoperative evaluation can be carried out. It is helpful for clinicians to evaluate and improve preoperative planning and post-operative measurement and evaluation of surgical effect. In terms of measurement accuracy, a large number of literatures reported that the accuracy of EOS 2D measurement is comparable to that of general radiology measurement, while the accuracy of EOS 3D reconstruction measurement is comparable to that of CT and MRI. Based on the technical characteristics and advantages of EOS, this paper reviews the literature reports and research progress of EOS in evaluating the accuracy of lower limb alignment.

Force decay evaluation of latex and non-latex orthodontic intraoral elastics: in vivo study

ABSTRACT Objective: This clinical study was conducted in order to evaluate force decay over time of latex and non-latex orthodontic intraoral elastics. Methods: Patients (n = 15) were evaluated using latex and non-latex elastics in the periods of : 0, 1, 3, 12 and 24 hours. The rubber bands were transferred to the testing machine (EMIC DL-500 MF), and force values were recorded after stretching the elastic to a length of 25mm. Paired t test was applied and analysis of variance (ANOVA) was used to evaluate the variation of force generated. LSD (Fisher's least significant difference) post-hoc test was thus employed. Results: As regards the initial forces (zero time), the values of force for non-latex elastic were slightly higher than for the latex elastic. In the subsequent times, the forces generated by the latex elastic showed higher values. Regarding the material degradation, at the end of 24 hours the highest percentage was observed for non-latex elastic. Conclusions: The latex elastics had a more stable behavior during the studied period, compared with non-latex.

RESUMO Objetivo: o objetivo deste estudo clínico foi avaliar e comparar o comportamento dos elásticos de látex e não látex quanto à perda de força ao longo do tempo. Método: os pacientes (n = 15) foram avaliados usando ambos os tipos de material (látex e não látex) em cada tempo: 0, 1, 3, 12 e 24 horas. Os elásticos foram transferidos para a máquina de ensaios mecânicos (EMIC DL-500 MF) e os valores de força foram registrados após a distensão dos elásticos a uma distância de 25 mm. Foi aplicado o teste t pareado, e a análise de variância (ANOVA) foi realizada para verificar a variação das forças geradas em todos os tempos estudados. Em seguida, o teste post-hoc LSD (Fisher's least significant difference) foi aplicado. Resultados: quanto às forças iniciais (tempo zero), os valores de força dos elásticos não látex foram ligeiramente maiores do que dos elásticos de látex. Nos tempos subsequentes, as forças geradas pelos elásticos de látex apresentaram valores superiores às geradas pelos elásticos não látex. Em relação à degradação do material, ao fim do período de 24 horas, o maior percentual foi observado pelos elásticos não látex. Conclusões: os elásticos de látex apresentaram comportamento mais estável durante o período de estudo, em comparação aos não látex.

Avaliação radiográfica da interface de reparo em resina bulk fill / Radiographic evaluation of repair interface in bulk fill resin

Objetivo: avaliar radiograficamente a interface de reparo em resina bulk fill (Opus bulk fill ­ FGM) com diferentes protocolos de adesão. Metodologia: foram confeccionados 30 corpos de prova em formato de cubo, nas dimensões de 4mm x 6mm. Os corpos foram randomizados e divididos entre os grupos: G1: ácido fosfórico a 37% (Dentsply) + adesivo (Ambar ­ FGM); G2: ácido fosfórico a 37% (Dentsply) + silano (Prosil ­ FGM) + adesivo (Ambar­FGM) e G3: Adesivo auto-condicionante (Ambar universal ­ FGM). Após os tratamentos, os corpos foram posicionados em uma matriz metálica de 4mm x 8mm para receber novos incrementos de resina bulk fill. Para análise do reparo, as amostras foram submetidas a radiografias digitais (Micro Imagem), com disparo de 0,16 segundos. Aplicou-se o efeito de contraste filtro de tele MI para permitir a avaliação visual. Para análise estatística foi utilizado o teste exato de Fisher. Resultados: o grupo 2 apresentou em metade dos espécimes avaliados, uma interface não visível, porém, não diferiu estatisticamente dos outros grupos que em sua maioria apresentaram a interface visível em mais de 50% da extensão do reparo. Conclusão: os protocolos realizados na interface da resina bulk fill não foram suficientes para gerar diferenças entre as imagens dos grupos tratados.

Objective: evaluate radiographically repair interface in bulk fill resin (Opus bulk fill-FGM) with different protocols of adhesion. Metodology: 30 specimens on the dimensions of 4 mm x 6 mm were made in cube formate. The specimens were randomized and divided between the groups: G1: phosphoric acid at 37% (Dentsply) + sticker (Ambar-FGM), G2: phosphoric acid at 37% (Dentsply) + silane (Prosil-FGM) + sticker (Ambar-FGM) and G3: Self-etching adhesive (universal Amber-FGM). After the treatments, the specimens were placed in a 4 mm x 8 mm metal matrix to receive new increments of resin bulk fill. For the repair analysis, samples were submitted to digital x-rays (Micro image), with triggering of 0.16 seconds. The filter contrast effect tele filter MI to allow visual assessment was applied. For statistical analysis we used the Fisher exact test. Results: group 2 presented in half of the specimens evaluated a not visible interface, however did not differ statistically from the other groups in that in their majority presented the visible interface in more than 50% of the repair extent. Conclusion: the protocols carried out in bulk fill resin interface were not sufficient to generate differences between the images of the treated groups.

Comparison of deflection forces of esthetic archwires combined with ceramic brackets

Abstract Coated archwires and ceramic brackets have been developed to improve facial esthetics during orthodontic treatment. However, their mechanical behavior has been shown to be different from metallic archwires and brackets. Therefore, the aim of this study was to compare the deflection forces in coated nickel-titanium (NiTi) and esthetic archwires combined with ceramic brackets. Material and Methods Non-coated NiTi (NC), rhodium coated NiTi (RC), teflon coated NiTi (TC), epoxy coated NiTi (EC), fiber-reinforced polymer (FRP), and the three different conventional brackets metal-insert polycrystalline ceramic (MI-PC), polycrystalline ceramic (PC) and monocrystalline ceramic (MC) were used. The specimens were set up on a clinical simulation device and evaluated in a Universal Testing Machine (Instron). An acrylic device, representative of the right maxillary central incisor was buccolingually activated and the unloading forces generated were recorded at 3, 2, 1 and 0.5 mm. The speed of the testing machine was 2 mm/min. ANOVA and Tukey tests were used to compare the different archwires and brackets. Results The brackets presented the following decreasing force ranking: monocrystalline, polycrystalline and polycrystalline metal-insert. The decreasing force ranking of the archwires was: rhodium coated NiTi (RC), non-coated NiTi (NC), teflon coated NiTi (TC), epoxy coated NiTi (EC) and fiber-reinforced polymer (FRP). At 3 mm of unloading the FRP archwire had a plastic deformation and produced an extremely low force in 2; 1 and 0.5 mm of unloading. Conclusion Combinations of the evaluated archwires and brackets will produce a force ranking proportional to the combination of their individual force rankings.

Testing System for Biomechanical Properties of Bone / 中国医疗器械杂志

A novel testing system is designed to simulate the mechanical performance and evaluate the biomechanical properties of the bone and the corresponding bone fixator. It is mainly composed of movement platform and servo motor system, sensors and hardware circuit system and software system. In order to prove the feasibility of the design, on the basis of the calibration for the force sensor, the fatigue experiment is carried out using the tibia of the sheep. It is concluded from the result that under the condition of 1 Hz in frequency, 50 kg in loading force and 18 000 cycles, the bone fixator can be still in good condition, which proves the feasibility of the design.

Structural and mechanical characterization of custom design cranial implant created using additive manufacturing

Background: Reconstruction of customized cranial implants with a mesh structure using computer-assisted design and additive manufacturing improves the implant design, surgical planning, defect evaluation, implant-tissue interaction and surgeon's accuracy. The objective of this study is to design, develop and fabricate cranial implant with mechanical properties closer to that of bone and drastically decreases the implant failure and to improve the esthetic outcome in cranial surgery with precision fitting for a better quality of life. A customized cranial mesh implant is designed digitally, based on the Digital Imaging and Communication in Medicine files and fabricated using state of the Art-Electron Beam Melting an Additive Manufacturing technology. The EBM produced titanium implant was evaluated based on their mechanical strength and structural characterization. Results: The result shows, the produced mesh implants have a high permeability of bone ingrowth with its reduced weight and modulus of elasticity closer to that the natural bone thus reducing the stress shielding effect. Scanning electron microscope and micro-computed tomography (CT) scanning confirms, that the produced cranial implant has a highly regular pattern of the porous structure with interconnected channels without any internal defect and voids. Conclusions: The study reveals that the use of mesh implants in cranial reconstruction satisfies the need of lighter implants with an adequate mechanical strength, thus restoring better functionality and esthetic outcomes for the patients.

Fundamentos biomecánicos de la lucha deportiva / Biomechanical fundamentals of sports wrestling

La práctica de la lucha ha permitido elaborar las estructuras más efectivas de las acciones técnicas, las cuales pueden ser divididas en acciones de ataques, defensas y contraataques. Los luchadores que tienen un buen desarrollo técnico dominan a menudo a contrarios que los superan en fuerza física. Con dicho fin, recurren a movimientos que, con su ejecución correcta y con una exacta aplicación y dirección de las fuerzas interiores y exteriores, forman una estructura de la llave, defensa y contrallave que aseguran una ventaja en fuerza o permiten ganar tiempo. Para desentrañar las leyes de la técnica de la lucha es necesario analizar todos los movimientos fundamentales de los luchadores. Este análisis es conveniente realizarlo, en primer lugar, con el estudio de la interacción de la fuerza mecánica que surge en la ejecución de las acciones técnicas. Por ello, el objetivo del estudio es plantear los fundamentos biomecánicos en el proceso de los ejercicios físicos y el análisis de las acciones motoras del luchador como sistema de movimientos activos recíprocamente relacionados(AU)

The wrestling practice has allowed the elaboration of most effective structures of the technical actions, which can be divided into actions of attacks, defenses, and counterattacks. The fighters who have a good technical development often dominate opponents who overcome them in physical strength. To this end, they resort to movements that, with their correct execution and with an exact application and direction of the internal and external forces, form a technique structure, defense and counter-technique that assure an advantage in strength or allow time. To unravel the technique laws of wrestling it is necessary to analyze all fundamental movements of the fighters. This analysis is convenient to do, first, with the study of mechanical force interaction that arises in the technical actions execution. Therefore, the study objective is to propose the biomechanical fundamentals to process of physical exercises and motor actions analysis in wrestling as a system of active movements related reciprocally(AU)

Propriedades mecânicas de dois padrões de sutura e dois tipos de fios aplicados às tenorrafias dos equinos / Tenorrhaphy in horses: comparison of the mechanical properties of two different suture patterns and suture materials

As lesões traumáticas dos membros que resultam em secções tendíneas são problemas comuns na clínica equina. Diversas complicações têm sido associadas à reparação dos tendões nessa espécie. O objetivo do presente trabalho foi avaliar biomecanicamente dois padrões de sutura e dois diferentes materiais aplicados às tenorrafias. Vinte e quatro peças de tendão flexor digital profundo de equinos foram seccionadas e suturadas em padrão locking loop duplo (grupo 1, com polipropileno; grupo 2, com poliglactina) ou em padrão locking loop simples associado à sutura de epitendão (grupo 3, com polipropileno; grupo 4, com poliglactina). Os corpos de prova foram submetidos a ensaios mecânicos de tração, em que se determinaram valores de força mínima, força máxima e pico de força, além do afastamento observado entre os cotos durante o pico máximo de força. Para avaliação dos resultados, foram utilizados os métodos ANOVA e os não paramétricos de Kruskal-Wallis e Mann-Whitney (P<0,05). Os maiores valores de força máxima foram documentados no grupo 3. Os valores de força mínima foram maiores nos grupos 3 e 4 que nos grupos 1 e 2, mas não diferiram significativamente entre os grupos 3 e 4. Os valores de pico de força foram maiores nos grupos 1 e 2 que no grupo 4, mas não diferiram significativamente no grupo 3. O afastamento foi maior nos grupos 1 e 2 quando comparados aos grupos 3 e 4. O padrão locking loop simples, com sutura de epitendão, atingiu maior resistência quando avaliado afastamento de até 3 milímetros entre os cotos tendíneos, sendo considerado padrão de escolha para aplicação clínica, tendo em vista os resultados obtidos neste trabalho.(AU)

Traumatic distal limb injuries resulting in tendon rupture are common in equine practice. Several complications have been associated with tendon repair in horses. The aim of this study was to compare the biomechanical properties of two tenorrhaphy techniques using two different suture materials. Twenty-four equine deep digital flexor tendon specimens were transected and sutured with the double locking loop pattern (polypropylene, group 1; polyglactin, group 2) or the single locking loop pattern with peripheral epitendon suture (polypropylene, group 3; polyglactin, group 4). Specimens were submitted to mechanical strain testing. Maximum, minimum and peak strain, and maximum, minimum and peak gap formation were evaluated. ANOVA and the non-parametric Kruskal-Wallis and Mann-Whitney tests were used (P<0.05). Higher maximum strength values were documented in group 3. Minimum strength values were higher in groups 3 and 4 than 1 and 2, but did not differ significantly between groups 3 and 4. Peak strength values were higher in groups 1 and 2 than 4, but did not differ significantly from group 3. Gap formation was greater in groups 1 and 2 than 3 and 4. The single locking loop pattern with epitendon suture performed with polypropylene had greater resilience, yielded lesser gap formation (3 mm) and is the pattern of choice for clinical application based on the results of this study.(AU)

Development and mechanical properties of a locking T-plate / Desenvolvimento e as propriedades mecânicas de uma placa bloqueada em formato de T

This study aimed to develop a locking T-plate and to evaluate its mechanical properties in synthetic models. A titanium 2.7mm T-plate was designed with a shaft containing three locked screw holes and one dynamic compression hole, and a head with two locked screw holes. Forty T-shaped polyurethane blocks, and 20 T-plates were used for mechanical testing. Six bone-plate constructs were tested to failure, three in axial compression and three in cantilever bending. Fourteen bone-plate constructs were tested for failure in fatigue, seven in axial compression and seven in cantilever bending. In static testing higher values of axial compression test than cantilever bending test were observed for all variables. In axial compression fatigue testing all bone-plate constructs withstood 1,000,000 cycles. Four bone-plate constructs failure occurred before 1,000,000 cycles in cantilever bending fatigue testing. In conclusion, the locking T-plate tested has mechanical properties that offer greatest resistance to fracture under axial loading than bending forces.(AU)

O objetivo deste estudo foi desenvolver uma placa bloqueada em formato de T e avaliar as propriedades mecânicas em um modelo sintético. Uma placa-T em liga de titânio 2,7mm foi desenhada com uma haste contendo três orifícios para parafusos bloqueados e um orifício para realização de compressão dinâmica. 40 blocos de poliuretano em formato de T e 20 placas-T foram utilizados para os ensaios mecânicos. Seis montagens osso-placa foram testados até a falha, sendo três em força de compressão axial e três em flexão engastada. 14 montagens osso-placa foram testadas até a falha em fatiga, sendo 7 em força de compressão axial e 7 em flexão engastada. No teste estático, os valores mais altos foram observados em todas as variáveis no teste de compressão axial quando comparado à flexão engastada. Já nos testes de fadiga na força de compressão axial, todas as montagens osso-placa resistiram à 1000000 de ciclos. No teste de fadiga em flexão engastada, quatro montagens osso-placa falharam antes de alcançarem 1000000 de ciclos. Em conclusão, a placa-T estudada apresenta propriedades mecânicas que oferecem uma melhor resistência em estabilizar as fraturas na atuação das forças de compressão axial que nas forças de flexão.(AU)