Evaluation of safety and effectiveness of NAD in different clinical conditions: a systematic review.

Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide cofactor that is present in cells and in several important biological processes, including oxidative phosphorylation and production of adenosine triphosphate, DNA repair, calcium-dependent secondary messenger and gene expression. The purpose of this systematic review is to examine whether the coenzyme formulae NAD+ and NADH are safe and effective when acting as a supplement to humans. This systematic review of randomized clinical trials performed a search in six electronic databases: PubMed, MEDLINE (ovid), Embase, Cochrane CENTRAL (clinical trials), Web of Science, and Scopus. Secondary search included the databases (e.g., Clinical trials.gov, Rebec, Google Scholar - advance). Two reviewers assessed and extracted the studies independently. The risk of bias in studies was performed using version 2 of the Cochrane risk of bias tool for randomized trials. This review includes 10 studies, with a total of 489 participants. The studies included different clinical conditions, such as chronic fatigue syndrome (CFS), older adults, Parkinson's disease, overweight, postmenopausal prediabetes, and Alzheimer's disease. Based on studies, the supplementation with NADH and precursors was well tolerated and observed clinical results such as, a decrease in anxiety conditions and maximum heart rate was observed after a stress test, increased muscle insulin sensitivity, insulin signaling. Quality of life, fatigue intensity, and sleep quality among others were evaluated on patients with CFS. All studies showed some side effects, thus, the most common associated with NADs use are muscle pain, nervous disorders, fatigue, sleep disturbance, and headaches. All adverse events cataloged by the studies did not present a serious risk to the health of the participants. Overall, these findings support that the oral administration of NADH can be associated to an increase in general quality of life and improvement on health parameters (e.g., a decrease in anxiety, maximum heart rate, inflammatory cytokines in serum, and cerebrospinal fluid). NADH supplementation is safe and has a low incidence of side effects. Future investigations are needed to evidence the clinical benefits regarding specific diseases and doses administered.

Continuous Vertical Inside-Out Versus Traditional Vertical Inside-Out Meniscal Repair: A Biomechanical Comparison.

Background: Biomechanical assessment of meniscal repairs is essential for evaluating different meniscal suturing methods and techniques. The continuous meniscal suture technique is a newer method of meniscal repair that may have biomechanical differences compared with traditional techniques. Purpose: To evaluate the displacement, stiffness after cyclical loading, and load to failure for a continuous vertical inside-out meniscal suture versus a traditional vertical inside-out meniscal suture in a porcine medial meniscus. Study Design: Controlled laboratory study. Methods: A total of 28 porcine knees were acquired and divided into 2 test groups of 14 medial meniscus each. A 2.0-cm longitudinal red-white zone cut was made in the body of the medial meniscus for each knee. The continuous suture (CS) group received 4 vertical stitches performed with a continuous vertical meniscal suture technique, and the inside-out suture (IO) group received a traditional vertical suture with 4 stitches. Two traction tapes were passed between the sutures and positioned in the biomechanical testing fixture device. Each specimen underwent load-to-failure testing at 5 mm/s, and displacement, system stiffness, and maximum load to failure were compared between the groups. Results: The displacement after the cyclic test was 0.53 ± 0.12 and 0.48 ± 0.07 mm for the CS and IO groups, respectively. There was no significant difference between the groups (P = .2792). The stiffness at the ultimate load testing was 36.3 ± 1.9 and 35.3 ± 2.4 N/mm for groups CS and IO, respectively, with no significant difference between the groups (P = .2557). In the load-to-failure test, the ultimate load was 218.2 ± 63.9 and 238.3 ± 71.3 N in the CS and IO groups, respectively, with no significant group differences (P = .3062). Conclusion: A continuous vertical meniscal suture created a configuration for treating longitudinal meniscal lesions that was beneficial and biomechanically similar to a traditional vertical suture technique. Clinical Relevance: The study findings indicate that use of the continuous vertical inside-out meniscal suture technique is a possible therapeutic option.

A numerical study of the contact geometry and pressure distribution along the glenoid track.

The glenoid track geometry and the contact forces acting on the glenohumeral joint at static positions of 30°, 60°, 90° and 120° of abduction with 90° of external rotation were evaluated using a finite element model of the shoulder that, differently from most usual approximations, accounts the humeral head translations and the deformable-to-deformable non-spherical joint contact. The model was based on data acquired from clinical exams of a single subject, including the proximal humerus, scapula, their respective cartilages concerning the glenohumeral joint, and the rotator cuff and deltoid muscles. The forces acting on the glenohumeral joint were estimated using a simulation framework consisting of an optimization procedure allied with finite element analysis that seeks the minimum muscle forces that stabilize the joint. The joint reaction force magnitude increases up to 680.25 N at 90° of abduction and decreases at further positions. From 60° onward the articular contact remains at the anterior region of the glenoid cartilage and follows an inferior to superior path at the posterior region of the humeral head cartilage. The maximum contact pressure of 3.104 MPa occurs at 90° abduction. Although translating inferiorly throughout the movement, the projection of the humeral head center at the glenoid plane remains at the central region of the glenoid surface. The model results qualitatively matched the trends observed in the literature and supports the consideration of the translational degrees of freedom to evaluate the joint contact mechanics.

Influence of acupuncture needle physical-chemical properties on needling quality.

OBJECTIVES: This study analyzed the physical-chemical properties of three different brands of acupuncture needle, classified by acupuncturists as high (A), medium (B) and low (C) quality. METHODS: Experienced acupuncturists, rated, in terms of perceived needling quality, three acupuncture needle brands as high (A), medium (B) and low (C) quality. Next, scanning electron microscopy (SEM) images of the tip and surface finish of the needles of each brand were analyzed. A mechanical test was developed and performed to evaluate the compressive force required to insert the needles through a smooth surface (silicon). In addition, X-ray fluorescence spectroscopy (XRF) and dispersive energy spectroscopy (DES) were conducted to analyze the material composition of the needles and presence of oxidation. RESULTS: SEM images revealed that needle brands A and B presented a sharper tip and a more regular surface finish in comparison to brand C. In the insertion test, needle brands A and B had similar performance characteristics, with A requiring less force to penetrate the silicon device when compared to B, while C failed to penetrate the silicon and complete the test. The XRF analysis did not reveal any differences in material composition between the three brands. However, brand C exhibited particles embedded on the needle surface and DES confirmed oxidation. CONCLUSION: This study demonstrates that perceived needling quality by acupuncturists can be correlated with physical-chemical properties of the needles, especially those related to finishing quality of the tip and the surface of the needles.

In vitro mechanical evaluation of spinal fixation rod connectors / Avaliação mecânica in vitro de conectores das hastes de fixação vertebral / Evaluación mecánica in vitro de conectores de varillas de fijación de la columna

ABSTRACT Objective Evaluate and compare the mechanical resistance and the fatigue behavior associated with the use of three different modalities of vertebral fixation system rod connectors through in vitro pre-clinical mechanical tests developed specifically for this application (linear, lateral with square connector and lateral with oblique connector). Methods Cobalt chromium rods 5.5 mm in diameter were used and coupled with three types of connectors: a) side rod with oblique connector, b) side rod with square connector, and c) rod and linear connectors. Quasi-static mechanical four-point bending and fatigue tests were performed. The variables measured were (I) the bending moment at the yield limit, (II) the displacement at the yield limit, (III) the rigidity of the system in flexion and (IV) the number of cycles until system failure. Results The linear system presented the greatest force and the greatest moment at the yield limit, as well as the greatest stiffness equivalent to bending. All specimens with square and oblique connectors endured 2.5 million cycles in the minimum and maximum conditions of applied moment. The specimens with linear connector endured 2.5 million cycles with fractions of 40.14% of the bending moment at the yield limit, but failed with levels of 60.17% and 80.27%. Conclusions Systems with linear connectors showed greater mechanical resistance when compared to systems with square and oblique connectors. All systems supported cyclic loads that mimic in vivo demands. Level of evidence V; In vitro research.

RESUMO Objetivo Avaliar e comparar a resistência mecânica e o comportamento em fadiga associados ao uso de três modalidades distintas de conectores de hastes do sistema de fixação vertebral por meio de ensaios mecânicos pré-clínicos in vitro desenvolvidos especificamente para essa aplicação (linear, lateral com conector quadrado e lateral com conector oblíquo). Métodos Foram usadas hastes de Cromo-cobalto de 5,5 mm de diâmetro acopladas a três modalidades de conectores: a) haste lateral com conector oblíquo, b) haste lateral com conector quadrado e c) haste e conector lineares. Foram realizados ensaios mecânicos quase-estáticos e de fadiga sob flexão em quatro pontos. As variáveis medidas foram (I) o momento fletor no limite de escoamento, (II) o deslocamento no limite de escoamento e (III) a rigidez do sistema em flexão e (IV) número de ciclos até a falha do sistema. Resultados O sistema linear apresentou a maior força e o maior momento no limite de escoamento, bem como maior rigidez equivalente à flexão. Todos os corpos de prova com conectores quadrados e oblíquos suportaram 2,5 milhões de ciclos nas condições mínimas e máximas de momento aplicado. Os corpos de prova com conector linear suportaram 2,5 milhões de ciclos com frações de 40,14% do momento fletor no limite do escoamento, porém falharam com níveis de 60,17% e 80,27%. Conclusões Os sistemas com conectores lineares apresentaram maior resistência mecânica quando comparados aos sistemas com conectores quadrados e oblíquos. Todos os sistemas suportaram carregamentos cíclicos que mimetizam as solicitações in vivo. Nível de evidencia V; Pesquisa in vitro.

RESUMEN Objetivo Evaluar y comparar la resistencia mecánica y el comportamiento de fatiga asociado al uso de tres modalidades distintas de conectores de varilla del sistema de fijación vertebral a través de ensayos mecánicos preclínicos in vitro desarrollados específicamente para esta aplicación (lineal, lateral con conector cuadrado y lateral con conector oblicuo). Métodos Se utilizaron varillas de cromo-cobalto de 5,5 mm de diámetro acopladas a tres tipos de conectores: a) varilla lateral con conector oblicuo, b) varilla lateral con conector cuadrado y c) varilla y conector lineales. Se realizaron ensayos mecánicos y de fatiga cuasi-estáticos y ensayos por flexión de cuatro puntos. Las variables medidas fueron (I) el momento flector en el límite elástico, (II) el desplazamiento en el límite elástico y (III) la rigidez del sistema en flexión y (IV) el número de ciclos hasta la falla del sistema. Resultados El sistema lineal presentó la mayor fuerza y el mayor momento en el límite elástico, así como la mayor rigidez equivalente a la flexión. Todas las probetas con conectores cuadrados y oblicuos soportaron 2,5 millones de ciclos en las condiciones mínimas y máximas de momento aplicado. Las probetas con conector lineal soportaron 2,5 millones de ciclos con fracciones del 40,14% del momento flector en el límite elástico, pero fallaron con niveles de 60,17% y 80,27%. Conclusiones Los sistemas con conectores lineales mostraron mayor resistencia mecánica en comparación con los sistemas con conectores cuadrados y oblicuos. Todos los sistemas admitían cargas cíclicas que imitan las solicitudes in vivo. Nivel de Evidencia V; Investigación in vitro.

Continuous Meniscal Suture in Radial Meniscal Tear: The Hourglass Technique.

The key to preventing early knee osteoarthritis is meniscal preservation. The main functions of the meniscus are impact absorption, mechanical load transmission, lubrication, joint stability, and proprioception. Radial lesions that extend to the joint capsule are called complete radial tears. This type of injury compromises 2 of the main meniscal functions, which are impact absorption and load distribution, which is equivalent, from a biomechanical perspective, to a total meniscectomy. In the recent past, the treatment of choice for this type of injury was partial meniscectomy. However, several studies have observed progressive joint degeneration after this type of treatment. Recently, different types of meniscal sutures involving radial lesions of the meniscus have been developed. It is believed that such repairs may bring a decrease in future osteoarthritis in this patient profile. The purpose of this article is to describe the steps of continuous meniscal suture for the treatment of radial tears of the medial and lateral menisci.

Comparative Biomechanical Study of Crosslinked Polyethylene Wear with 36-mm Ceramic Femoral Heads and with 32-mm Metal Femoral Heads.

Objective This study aims to compare the in vitro wear rate of crosslinked, high molecular weight polyethylene coupled to 36-mm diameter ceramic heads and 32-mm diameter metal heads. Methods Ceramic-on-polyethylene (36 mm) and metal-on-polyethylene (32 mm) tribological pairs were submitted to biomechanical tests in a simulator to determine the wear rate after 15 × 10 6 cycles. Results A statistically significant difference ( p = 0.0005) was detected when comparing the wear rate of assemblies with metallic heads (average wear: 14.12 mg/MC) and ceramic heads (average wear: 7.46 mg/MC). Conclusion The present study demonstrated the lower wear rate in prosthetic assemblies using 36-mm crosslinked ceramic-on-polyethylene tribological pairs compared to 32-mm crosslinked metal-on-polyethylene assemblies. This finding demonstrates the effectiveness of ceramic-on-polyethylene tribological pairs, even with large diameter heads.

Comparative Biomechanical Study of Crosslinked Polyethylene Wear with 36-mm Ceramic Femoral Heads and with 32-mm Metal Femoral Heads / Estudo biomecânico comparativo do desgaste do polietileno reticulado com cabeças femorais cerâmicas de 36 mm e com cabeças metálicas de 32 mm

Abstract Objective This study aims to compare the in vitro wear rate of crosslinked, high molecular weight polyethylene coupled to 36-mm diameter ceramic heads and 32-mm diameter metal heads. Methods Ceramic-on-polyethylene (36 mm) and metal-on-polyethylene (32 mm) tribological pairs were submitted to biomechanical tests in a simulator to determine the wear rate after 15 × 106 cycles. Results A statistically significant difference (p= 0.0005) was detected when comparing the wear rate of assemblies with metallic heads (average wear: 14.12 mg/MC) and ceramic heads (average wear: 7.46 mg/MC). Conclusion The present study demonstrated the lower wear rate in prosthetic assemblies using 36-mm crosslinked ceramic-on-polyethylene tribological pairs compared to 32-mm crosslinked metal-on-polyethylene assemblies. This finding demonstrates the effectiveness of ceramic-on-polyethylene tribological pairs, even with large diameter heads.

Resumo Objetivo: O objetivo do presente estudo foi comparar, in vitro, a taxa de desgaste do polietileno de alto peso molecular reticulado acoplado a cabeças cerâmicas de 36 mm de diâmetro e acoplado a cabeças metálicas de 32 mm de diâmetro. Métodos: Foram realizados ensaios biomecânicos em simulador de desgaste para os pares tribológicos cerâmica-poli (36 mm) e metal-poli (32 mm) a fim de verificar a taxa de desgaste após em 15 × 106 ciclos. Resultados: Na comparação entre as medidas de taxa de desgaste dos conjuntos com cabeças metálicas (média:14,12 mg/MC) e cerâmicas (média:7,46 mg/MC) houve diferença estatitsticamente significativa (p= 0,0005). Conclusão: O presente estudo demonstrou menor taxa de desgaste em conjuntos protéticos que utilizaram o par tribológico cerâmica-polietileno reticulado de 36 mm em comparação aos conjuntos com metal-polietileno reticulado de 32 mm. Tal achado demonstra a eficácia do par tribológico cerâmica-poli, mesmo com a utilização de cabeças de grande diâmetro.

Numerical study on the effect of stent shape on suture forces in stent-grafts.

Second-generation stent-grafts (SGs) have addressed many of the mechanical problems reported for first-generation endoprostheses, such as graft tear and stent rupture; however, suture wear and detachment due to pulsatile fatigue remains an issue. Numerical studies on the mechanical behavior of these endoprostheses usually model the attachment between stents and graft as a continuous ''tie'' constraint, which does not provide information on the mechanical loads acting on individual sutures. This paper presents a suitable approach for Finite Element (FE) simulations of SGs which allows for a qualitative evaluation of the loads acting on sutures. Attachment between stents and graft is modeled as rigid beams at discrete locations of the endoprostheses, and the reaction forces on the beams are analyzed. This modeling strategy is employed for four different SG models (two Z-stented commercial models and two circular-stented models) subjected to a severe 180° U-bend, followed by intraluminal pressurization. Results show that, for all models, the majority of sutures is experiencing fluctuating forces within a cardiac cycle (between 80 and 120 mmHg), which points to pulsatile fatigue as potential failure mode. In addition, the highest loads are concentrated in kinks and, for Z-stented models, at the apexes of stents. Moreover, suture loads for circular-stented models are lower than for Z-stented models, indicating better resistance to suture detachment. All these observations are in line with experimental results published in the literature, and, therefore, the procedure herein proposed may serve as a valuable tool in the development of new SG models with better suture resistance to pulsatile wear and fatigue.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation.

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures.

Influence of Processing Conditions on the Mechanical Behavior and Morphology of Injection Molded Poly(lactic-co-glycolic acid) 85:15.

Two groups of PLGA specimens with different geometries (notched and unnotched) were injection molded under two melting temperatures and flow rates. The mechanical properties, morphology at the fracture surface, and residual stresses were evaluated for both processing conditions. The morphology of the fractured surfaces for both specimens showed brittle and smooth fracture features for the majority of the specimens. Fracture images of the notched specimens suggest that the surface failure mechanisms are different from the core failure. Polarized light techniques indicated birefringence in all specimens, especially those molded with lower temperature, which suggests residual stress due to rapid solidification. DSC analysis confirmed the existence of residual stress in all PLGA specimens. The specimens molded using the lower injection temperature and the low flow rate presented lower loss tangent values according to the DMA and higher residual stress as shown by DSC, and the photoelastic analysis showed extensive birefringence.

An experimental methodology for arterial walls / Análise experimental de paredes arteriais

Numerical simulations of arterial walls allow a better understanding of the interaction between biological tissue and endoprosthesis (stents), which are used in aneurysms or atherosclerosis stenosis treatment. A reliable understanding of this interaction may help one to select, or even design, the best structure for a given clinical indication. The development of a realistic numerical simulation requires an appropriated definition of a constitutive model and the obtainment of experimental data useful to a parameter identification procedure. Biological tissues have different mechanical characteristics of materials commonly used for engineering applications, however the experimental data acquisition is a major challenge. Some examples of technical difficulties of experimental test in biological tissue are associated to the obtainment of samples, temperature and humidity control during storage, suitable gripping and geometric and strain measurements methods. Therefore, this paper presents an experimental methodology to perform uniaxial mechanical tests in pig arteries in order to provide useful information for material models of arterial walls. This study proposes the experimental procedure from the sample obtainment to the uniaxial experimental testing of the tissue in two directions (circumferential and longitudinal) at two strain rates. In order to shown the use of the experimental data into a suitable numerical model for arterial walls, a parameter identification procedure was performed to obtain material parameters of a viscoelastic anisotropic model with fiber dispersion for finite strains. Through the experimental methodology proposed it was possible to obtain useful data for the parameter identification. Moreover, the results demonstrate that the arterial walls mechanical behavior was properly represented by the selected model.

Simulações numéricas de paredes arteriais permitem um melhor entendimento da interação entre tecido biológico e endopróteses (stents), os quais são utilizados no tratamento de aneurismas e lesões obstrutivas ateroscleróticas. O melhor entendimento desta interação pode auxiliar na seleção do modelo ou no projeto da estrutura da endoprótese mais adequada para uma dada indicação clínica. A realização de simulações numéricas realísticas requer a definição apropriada de um modelo constitutivo e a obtenção de dados experimentais adequados para um procedimento de identificação de parâmetros. Diferentemente dos materiais usados comumente em engenharia, a aquisição de dados experimentais de tecidos biológicos representa um grande desafio. Alguns exemplos das dificuldades técnicas associadas aos testes experimentais de tecidos biológicos estão na obtenção de amostras, no controle de temperatura e humidade durante o armazenamento, na fixação adequada e na medição geométrica e de deformações. Portanto, o presente artigo apresenta uma metodologia experimental para realização de testes uniaxiais em artérias suínas, visando fornecer informações adequadas para modelos materiais de paredes arteriais. Este estudo propõe um procedimento experimental que abrange desde a obtenção da amostra até o ensaio uniaxial do tecido em duas direções (circunferencial e longitudinal), com duas taxas de velocidades. Para exemplificar o uso dos dados experimentais em um modelo numérico adequado para paredes arteriais, um procedimento de identificação de parâmetros foi realizado, obtendo parâmetros materiais de um modelo viscoelástico anisotrópico com dispersão de fibras para deformações finitas. Através da metodologia experimental proposta foi possível obter dados úteis para identificação de parâmetros. Além disso, os resultados demonstraram que o comportamento mecânico de paredes arteriais foi representado adequadamente pelo modelo selecionado.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin.

The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin

Abstract The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

Resumo O objetivo deste estudo foi comparar a resistência à fadiga de dentes restaurados com uma resina composta bulk fill, resina composta convencional de inserção incremental e dentes hígidos sem preparo. Vinte e oito pré-molares maxilares extraídos foram selecionados e divididos em quatro grupos conforme a resina composta e técnica de inserção: controle (C), resina composta convencional com inserção incremental (I) e resina composta bulk fill inserida em três (BF3) ou único incremento (BF1). O preparo das cavidades foi padronizado para todos os grupos. As amostras foram restauradas e submetidas ao testes de resistência à fadiga com uma frequência de 5 Hz. Foram aplicados 5.000 ciclos de carregamento senoidal inicial com valor de força mínima igual a 50 N e força máxima de 200 N. Após, foram aplicados estágios de 30.000 ciclos de carga com a força máxima sendo aumentada gradativamente a cada estágio, para 400, 600, 800, 1000, 1200 e 1400 N. O ensaio foi finalizado ao ser alcançado 185.000 ciclos de carga (número máximo de ciclos de carga), ou na fratura da amostra. A resistência à fadiga foi registrada para comparação usando a curva de sobrevivência de Kaplan-Meier e analisada pelo teste log-rank a um nível de significância de 0.05. As fraturas foram classificadas conforme a posição da falha - acima ou abaixo da junção cemento esmalte (JCE). A análise estatística da curva de sobrevivência de Kaplan-Meier pelo teste log-rank demonstrou diferença significativa entre os grupos (p=0.001). Na análise de fratura somente 28.58% das falhas foram abaixo da JCE para o grupo C, enquanto para os grupos I, BF1 e BF3 foram 42.85%, 85.71% e 85.71%, respectivamente. Os dentes restaurados com a resina composta bulk fill em ambas as técnicas de inserção apresentaram valores de resistência à fadiga similares àqueles dos dentes restaurados com a resina composta convencional pela técnica incremental. Entretanto, dentes hígidos mostraram uma menor porcentagem de fraturas abaixo da JCE e maior resistência à fadiga.

Biomechanical performance of Bio Cross-Pin and EndoButton for ACL reconstruction at femoral side: a porcine model

Abstract Introduction The method of graft fixation is critical in anterior cruciate ligament (ACL) reconstruction surgery. Success of surgery is totally dependent on the ability of the implant to secure the graft inside the bone tunnel until complete graft integration. The principle of EndoButton is based on the cortical suspension of the graft. The Cross-Pin is based on graft expansion. The aim of this study was to evaluate the biomechanical performance of EndoButton and Bio Cross-Pin to fix the hamstring graft at femoral side of porcine knee joints and evaluate whether they are able to support of loading applied on graft during immediate post-operative tasks. Methods Fourteen ACL reconstructions were carried out in porcine femurs fixing superficial flexor tendons with Titanium EndoButton (n = 7) and with 6 × 50 mm HA/PLLA Bio Cross-Pin (n = 7). A cyclic loading test was applied with 50-250 N of tensile force at 1 Hz for 1000 cycles. The displacement was measured at 20, 100, 500 and 1000 load cycles to quantify the slippage of the graft during the test. Single-cycle load-to-failure test was performed at 50 N/mm to measure fixation strength. Results The laxity during cyclic loading and the displacement to failure during single-cycle test were lower for the Bio Cross-Pin fixation (8.21 ± 1.72 mm) than the EndoButton (11.20 ± 2.00 mm). The Bio Cross-Pin (112.22 ± 21.20 N.mm–1) was significantly stiffer than the EndoButton fixation (60.50 ±10.38 N.mm–1). There was no significant difference between Bio Cross-Pin (failure loading: 758.29 ± 188.05 N; yield loading: 713.67 ± 192.56 N) and EndoButton strength (failure loading: 672.52 ± 66.56 N; yield loading: 599.91 ± 59.64 N). Both are able to support the immediate post-operative loading applied (445 N). Conclusion The results obtained in this experiment indicate that the Bio Cross-Pin technique promote stiffer fixation during cyclic loading as compared with EndoButton. Both techniques are able to support the immediate post-operative loading applied.

Fretting corrosion tests on orthopedic plates and screws made of ASTM F138 stainless steel

Introduction Although there has been significant progress in the design of implants for osteosynthesis, the occurrence of failures in these medical devices are still frequent. These implants are prone to suffer from fretting corrosion due to micromotion that takes place between the screw heads and plate holes. Consequently, fretting corrosion has been the subject of research in order to understand its influence on the structural integrity of osteosynthesis implants. The aim of this paper is to correlate the surface finish characteristics of bone plate-screw systems with fretting corrosion. Methods The surface finish (machined and polished) of five specimens taken from three commercial dynamic compression plates (DCP) were evaluated. For testing, the specimens were fixed with bone screws, immersed in a solution of 0.90% NaCl and subjected to a rocking motion with an amplitude of 1.70 mm and frequency of 1.0 Hz for 1.0 × 106 cycles, according to the ASTM F897 standard. Both, plate and screws were manufactured in Brazil with ASTM F138 stainless steel. Results Flaws on the hole countersink area and on the screw thread of some specimens were identified stereoscopically. At the end of the test all the specimens showed evidence of fretting corrosion with an average metal loss of 4.80 mg/million cycles. Conclusion An inadequate surface finish in some areas of the plates and screws may have favored the incidence of damage to the passive film, accelerating the fretting corrosion at the interfaces between the plate hole countersink and the screw head. Keywords Osteosynthesis, DCP, Bone plate, Screw, Fretting corrosion, Stainless steel.

Graft tendon slippage with metallic and bioabsorbable interference screws under cyclic load: a biomechanical study in a porcine model

Introduction The rupture of the anterior cruciate ligament (ACL) is the most common type of knee injury. Reconstructive surgery is the ‘gold standard’ treatment. During the immediate post-operative period, the fixation of the graft is entirely dependent on the ability of the grafted implant to be secured inside the bone tunnel under the cyclical loads associated with daily tasks. Poor fixation can lead to graft slippage, thus impairing the healing and integration of the graft. The aim of this study was to evaluate the biomechanical performance of tendon graft fixation devices with metallic and bioabsorbable interference screws. Methods Twenty ACL reconstructions were carried out in porcine tibias using deep flexor tendons to fix 9 × 20 mm metallic (n=10) and PLLA 70/30 bioabsorbable screws (n=10). To verify the ability of a construct to resist immediate postoperative (PO) rehabilitation protocols for immediate load bearing, a cyclic loading test was applied with 50-250 N of tensile force at 1 Hz for 1000 cycles, and the displacement was measured at 10, 50, 100, 500 and 1000 load cycles to quantify the slippage of the graft during the test. After the cyclic loading test, a single-cycle load-to-failure test was applied. Results The slippage of the graft using metallic screws did not differ (P = 0.616) from that observed when using bioabsorbable screws. Conclusion The results obtained in this experiment indicate that metallic screws may promote a similar amount of graft slippage during low cyclic loading as bioabsorbable screws. Additionally, there was no difference in the biomechanical performance of these two types of screws during high failure loads.

Simulação numérica tridimensional da mecânica do joelho humano / Three-dimensional numerical simulation of human knee joint mechanics

OBJETIVO: Por ser a articulação mecanicamente mais solicitada de nossa estrutura e pelo grande número de lesões associadas, motivaram a construção de um modelo tridimensional da articulação do joelho humano para simular a cinemática da articulação e obter as solicitações mecânicas nos principais ligamentos durante o movimento de flexão do joelho. Essas informações podem futuramente ser empregada como ferramenta de apoio à decisão médica em ortopedia, fornecendo subsídios na escolha do procedimento cirúrgico. MÉTODOS: Método dos Elementos Finitos foi utilizado para construir um modelo biomecânico, tridimensional, da articulação do joelho. Nesse modelo com seis graus de liberdade é aplicado movimento de flexão/extensão sendo os demais cinco graus de liberdade governados pelas interações entre os componentes da articulares. RESULTADOS: Foram obtidas informações dos movimentos, das rotações interna/externa e adução/abdução, das translações anterior/posterior, lateral/medial e superior/inferior e dos esforços nos quatro principais ligamentos articulares, no decorrer de um amplo movimento de flexão/extensão. Estes valores foram comparados, de forma qualitativa, com valores equivalentes obtidos na literatura. CONCLUSÃO: A análise de resultados permitiu observar que vários aspectos cinemáticos são satisfatoriamente reproduzidos. A pré-carga inicial dos ligamentos e o posicionamento das inserções ligamentares no modelo mostraram-se variáveis relevantes nos resultados.

OBJECTIVE: The knee joint is the part of our structure upon which most mechanical demands are placed and a large number of lesions are associated to it. These factors motivated the construction of a three-dimensional model of the human knee joint in order to simulate joint kinematics and obtain the mechanical demands on the main ligaments during knee flexion movements. METHODS: The finite elements method was used to build a three-dimensional, biomechanical model of the knee joint. In this model with six degrees of freedom, the flexion/extension movement is applied, while the other five degrees of freedom are governed by the interactions between joint components. RESULTS: Data was collected on the movements, on the internal/external and adduction/ abduction rotations, on the anterior/posterior, lateral/medial and upper/lower translations, and on the forces acting upon the four main joint ligaments, during a wide flexion/extension movement. These values were qualitatively compared with comparable values available in the literature. CONCLUSIONS: It was observed through an analysis of the results that several kinematic aspects are satisfactorily reproduced. The initial pre-load of the ligaments and the positioning of the ligament insertions in the model were shown to be relevant variables in the results.

Identificação do conteúdo de frequências presente na força de reação do solo medida com plataforma de forças / Frequency present in reaction force of the floor measure with force platform

In physicai activities the human body exerts forces against Lhe floor. In activities such as running and jumping the forces are exerted through the feet. Actually it is known that magnitude and direction studies of these forces, and the manners of their changes in time, supply valuable information about the performance obtained in movement. In this sense force platforms are used, being able to measure the action force exerted on their contact surface and the respective torque, allowing the determination of three orthogonal forces components (Fz, Fy, Fx) and torque around the three orthogonal axes (Mz, My, Mx) simultaneously. However, the force platform utilization depends on its capacity to measure dynamic forces precisely, because the forces applied to the platform are dynamic in nature. So, the determination of the vibration frequency components excited by the movement in study is fundamental in the correct model platform choice or design. According this work presents a methodto assess this determination and demonstrates an example of application in the long jump takeoft movement