Biomechanical analysis of narrow dental implants for maxillary anterior rehabilitation / Análise biomecânica de implantes de diâmetro reduzido para reabilitação da região anterior da maxila

Introdução: O conhecimento da biomecânica de implantes de diâmetro reduzido indica dimensões seguras para uso clínico. Objetivo: O objetivo do presente estudo foi comparar biomecanicamente implantes de diâmetro regular e reduzido para suporte de próteses implantossuportadas unitárias na região anterior da maxila por meio de análise de elementos finitos 3D (3D-FEA). Material e método: Quatro modelos 3D-FEA foram desenvolvidos a partir de recomposição de tomografia computadorizada e dados da literatura: um bloco ósseo na região incisiva lateral superior direita com implante e coroa. M1: 3,75 x 13 mm, M2: 3,75 x 8,5 mm, M3: 2,9 x 13 mm e M4: 2,9 x 8,5 mm. Foi aplicada carga de 178 N nos ângulos 0, 30 e 60 graus em relação ao longo eixo do implante. Foram avaliados mapas de tensão de Von Mises, tensão principal máxima e microdeformação. Resultado: M3 e M4 apresentaram maiores valores de tensão e microdeformação que M1 e M2, principalmente quando foram aplicadas forças inclinadas. Porém, M3 apresentou comportamento biomecânico melhor do que M4. Conclusão: Pode-se concluir que reduzir o diâmetro dos implantes pode prejudicar a biomecânica durante a aplicação de forças, mas a distribuição e intensidade das tensões, bem como os valores de microdeformação podem ser melhorados se o comprimento do implante for aumentado

Introduction: Narrow diameter implants biomechanics knowledge indicates safe dimensions for clinical use. Objective: Purpose of the present study was biomechanically to compare regular and narrow diameter implants to support single implant-supported prosthesis in the anterior region of the maxilla by 3D finite element analysis (3D-FEA). Material and method: Four 3D-FEA models were developed form CT scan recompositing and literature data: a bone block in the right upper lateral incisive region with implant and crown. M1: 3.75 x 13 mm, M2: 3.75 x 8.5 mm, M3: 2.9 x 13 mm and M4: 2.9 x 8.5 mm. It was applied load was of 178 N at 0, 30 and 60 degrees in relation to implant long axis. Von Mises stress, maximum principal stress and microdeformation maps were evaluated. Result: M3 and M4 did show higher tension and higher microdeformation values than M1 and M2, especially when inclined forces were applied. However, M3 presented enhanced biomechanical behavior than M4. Conclusion: It can be concluded that reduce the diameter of the implants can disadvantage to the biomechanics during the application of forces, but the distribution and intensity of the stresses, as well as the micro deformation values can be improved if the length of the implant is increased

Comparison of the High Cycle Fatigue Behavior of the Orthodontic NiTi Wires: An in Vitro Study

Abstract Objective: To compare the high-cycle fatigue behavior of four commercially available NiTi orthodontic wires. Material and Methods: Twelve NiTi orthodontic wires, round, 0.016-in, three per brand, were selected and divided into four groups: G1 - Heat-activated NiTi, G2 - Superelastic NiTi, G3 - Therma-Ti, and G4 - CopperNiTi. The atomic absorption spectrometry method was used to determine the chemical composition of investigated NiTi wires. We also performed a fatigue test at three-point bending using a universal testing machine for 1000 cycles in a 35 °C water bath. For the first and thousandth cycle, the average plateau load and the plateau length were determined in the unloading area of the force versus displacement diagram. In addition, we calculated the difference between the average plateau load of the first and thousandth cycle (∆F), as well as the difference between the plateau length of both cases (∆L). Results: According to our results, there were no significant differences between the average plateau load of the first and thousandth cycles of each group (p>0.05) and in the plateau length of the first and thousandth cycles of the groups (p>0.05). Conclusion: There were no significant differences between the groups changing the superelasticity property after high-cycle fatigue.

Microhardness and Diametral Compression Strength of Single Fill Composite

ABSTRACT: To evaluate Knoop microhardness and diametral compression strength at different polymerization times. A total of 80 cylindrical samples with Filtek resin™ One Bulk Fill were made to perform the in vitro study, using half of total samples (n=40) for each test and divided equally between groups (n=10). All samples were made according to ISO 4049 using 2 mm thickness Teflon matrix and a central orifice with 4 mm diameter. Four different times of light-curing in Standard mode suggested by the light-unit manufacturer were selected, therefore, group 1 samples (G1) were light-cured for 5 seconds; group 2 (G2) for 10 seconds; group 3 (G3) for 15 seconds, and group 4 (G4) for 20 seconds. A radiant display, which means a power in mW/cm2 by time in seconds was expressed in Joules (J). The samples were stored in a dark container with distilled water at a temperature of 37°C for 48 hours before testing. One-way analysis of variance (ANOVA) with T-Test (LSD) of multiple comparisons of the mean values of Knoop hardness and diametral compression strength was performed, with significance index α=0.05. Regarding the Knoop microhardness test, G1 (35.73 ± 6.2) presented the lowest values, followed by G2, while G3 and G4 did not present statistical differences between them. For the diametral compression test, G1 (1387.76 ± 190.51) obtained the lowest value when compared to the other groups. G2, G3, and G4 did not present significant statistical differences. The different polymerization times influenced the Knoop microhardness and the diametral compression strength of Bulk Fill resin.

RESUMEN: El objetivo de este trabajo fue evaluar la microdureza Knoop y la resistencia a la compresión diametral en diferentes tiempos de polimerización. En el estudio realizado in vitro, se analizó un total de 80 muestras cilíndricas con la resina Filtek™ One Bulk Fill, utilizando la mitad (n=40) para cada prueba realizada y dividida en partes iguales entre los grupos (n=10). Todas las muestras se tomaron de acuerdo con ISO 4049 utilizando matrices de teflón de 2 mm de espesor y orificio central con 4 mm de diámetro. Se seleccionó cuatro veces el fotocurado de manera estándar, sugerido por el fabricante. Por lo tanto, las muestras del grupo 1 (G1) se fotopolimerizaron durante 5 segundos; grupo 2 (G2) durante 10 segundos; grupo 3 (G3) durante 15 segundos y grupo 4 (G4) durante 20 segundos. La exposición radiante, que indica la potencia en mW / cm2 a lo largo del tiempo en segundos, se expresó en julios (J). Las muestras se almacenaron en un recipiente oscuro con agua destilada en una estufa a una temperatura de 37°C durante 48 horas antes del ensayo. Se realizó para comparaciones múltiples de los valores medios, análisis de varianza (ANOVA) de un criterio con la prueba T (LSD) tanto de la dureza de Knoop como de la compresión diametral con un índice de significación α=0.05. Con respecto a la prueba de microdureza de Knoop, G1 (35,73 ± 6,2) tuvo los valores más bajos, seguido de G2, mientras que G3 y G4 no mostraron diferencias estadísticas entre ellos. Para la prueba de compresión diametral, G1 (1387.76 ± 190.51) obtuvo el valor más bajo en comparación con los otros grupos. G2, G3 y G4 no presentaron diferencias estadísticamente significativas. Los diferentes tiempos de polimerización influyeron en la microdureza de Knoop y la resistencia a la compresión diametral de la resina compuesta mono incremental.

Estrés y desempeño laboral de los colaboradores de una red de salud / Stress and work performance of a health network staff

El estudio tuvo el objetivo de establecer la relación entre el estrés y el desempeño laboral de los colaboradores de la Red de Salud de Trujillo en 2019. Durante el proceso investigativo se siguió una metodología no experimental, a través de un estudio correlacional, de corte transversal, con un enfoque mixto; en el que participaron 98 colaboradores de ese entorno. Los investigadores realizaron el análisis empleando dos variables relacionadas con el ambiente laboral: estrés y desempeño. El 98% de los colaboradores mostró niveles medio y alto de estrés laboral y el 39,8% tuvo un desempeño laboral catalogado como regular. Se concluyó que el coeficiente de Rho de Spearman permitió establecer una correlación negativa y moderada entre estrés y desempeño laborales.

The study aimed to establish the relationship between stress and work performance of the staff of the Trujillo Health Network in 2019. During the research process, a non-experimental methodology was followed, through a correlational, cross-sectional study, with a mixed approach; in which 98 collaborators from that environment participated. The researchers carried out the analysis using two variables related to the work environment: stress and performance. Most of the collaborators (98%) showed medium and high levels of work stress and 39.8% had a work performance classified as regular. It was concluded that the Spearman's Rho coefficient allowed establishing a negative and moderate correlation between stress and work performance.

Acute Physical Stress Preconditions the Heart Against Ischemia/Reperfusion Injury Through Activation of Sympathetic Nervous System / Estresse Físico Agudo Precondiciona o Coração Contra a Injúria por Isquemia/Reperfusão Através da Ativação do Sistema Nervoso Simpático

Abstract Background: Stress is defined as a complicated state that related to homeostasis disturbances, over-activity of the sympathetic nervous system and hypothalamus-pituitary-adrenal axis responses. Cardiac preconditioning reduces myocardial damages. Objective: This study was designed to assess the cardioprotective effects of acute physical stress against ischemia/reperfusion (I/R) injury through the activation of the sympathetic nervous system. Methods: Thirty-two male Wistar rats were divided into four groups; (1) IR (n = 8): rats underwent I/R, (2) Acute stress (St+IR) (n = 8): physical stress induced 1-hour before I/R, (3) Sympathectomy (Symp+IR) (n = 8): chemical sympathectomy was done 24-hours before I/R and (4) Sympathectomy- physical stress (Symp+St+IR) (n = 8): chemical sympathectomy induced before physical stress and I/R. Chemical sympathectomy was performed using 6-hydroxydopamine (100 mg/kg, sc). Then, the hearts isolated and located in the Langendorff apparatus to induce 30 minutes ischemia followed by 120 minutes reperfusion. The coronary flows, hemodynamic parameters, infarct size, corticosterone level in serum were investigated. P < 0.05 demonstrated significance. Results: Physical stress prior to I/R could improve left ventricular developed pressure (LVDP) and rate product pressure (RPP) of the heart respectively, (63 ± 2 versus 42 ± 1.2, p < 0.05, 70 ± 2 versus 43 ± 2.6, p < 0.05) and reduces infarct size (22.16 ± 1.3 versus 32 ± 1.4, p < 0.05) when compared with the I/R alone. Chemical sympathectomy before physical stress eliminated the protective effect of physical stress on I/R-induced cardiac damages (RPP: 21 ± 6.6 versus 63 ± 2, p < 0.01) (LVDP: 38 ± 4.5 versus 43 ± 2.6, p < 0.01) (infarct size: 35 ± 3.1 versus 22.16 ± 1.3, p < 0.01). Conclusion: Findings indicate that acute physical stress can act as a preconditional stimulator and probably, the presence of sympathetic nervous system is necessary.

Resumo Fundamento: O estresse é definido como um estado complicado de distúrbios da homeostase, hiperatividade do sistema nervoso simpático e das respostas do eixo hipotálamo-hipófise-adrenal. O pré-condicionamento cardíaco diminui os danos do miocárdio. Objetivo: Esse estudo avaliou os efeitos cardioprotetores do estresse físico agudo contra a lesão por isquemia-reperfusão (I/R) através da ativação do sistema nervoso simpático. Métodos: Trinta e dois ratos machos Wistar foram divididos em quatro grupos; (1) IR (n = 8): ratos submetidos a I/R, (2) Estresse agudo (St+IR) (n = 8): estresse físico induzido 1 hora antes da I/R, (3) Simpatectomia (Symp+IR) (n = 8): a simpatectomia química foi realizada 24 horas antes da I/R e (4) Simpatectomia-estresse físico (Symp+St+IR) (n = 8): simpatectomia induzida antes do estresse físico e da I/R. A simpatectomia química foi realizada com 6-hidroxidopamina (100 mg/kg, SC). Em seguida, os corações foram isolados e colocados em aparato de Lagendorff por 30 minutos para induzir isquemia, seguida de reperfusão por 120 minutos. Os fluxos coronarianos, os parâmetros hemodinâmicos, o tamanho do infarto e os níveis de corticosterona plasmática foram investigados. Valores de p < 0,05 foram considerados significativos. Resultados: O estresse físico anterior à I/R pode melhorar a pressão desenvolvida no ventrículo esquerdo (PDVE) e duplo produto (DP), respectivamente, (63 ± 2 versus 42 ± 1,2, p < 0,05, 70 ± 2 versus 43 ± 2,6, p < 0,05) e reduzir o tamanho do infarto (22,16 ± 1,3 versus 32±1,4, p < 0,05) quando comparado com a I/R isoladamente. A simpatectomia química antes do estresse físico eliminou o efeito protetor do estresse físico sobre os danos cardíacos induzidos pela I/R (DP: 21 ± 6,6 versus 63 ± 2, p < 0,01) (PDVE: 38 ± 4,5 versus 43 ± 2,6, p < 0,01) (tamanho do infarto: 35 ± 3,1 versus 22,16 ± 1,3, p < 0,01). Conclusão: Os achados indicam que o estresse físico agudo pode funcionar como um estimulador pré-condicional e, provavelmente, a presença do sistema nervoso simpático é necessária.

Localization of Atypical Femoral Fracture on Straight and Bowed Femurs

BACKGROUND: To elucidate the effect of anterolateral bowing on the fracture height of atypical femoral fractures (AFFs), we separated the AFFs into 2 groups according to the presence of anterolateral femoral bowing (straight group and bowing group) and analyzed the fracture height. The aims of this study were to evaluate the clinical and radiological features of AFFs in the straight group and bowing group, and to determine which factors were associated with the fracture height of AFFs in the total cohort and each subgroup. METHODS: Ninety-nine patients with AFFs were included in this study (43 patients in the bowing group and 56 patients in the straight group). Clinical and radiological characteristics were compared between the groups. Multivariable linear regression analysis was performed to determine the effect of factors on fracture height. RESULTS: Patients in the straight group were younger, heavier, and taller, and had a higher bone mineral density, smaller anterior and lateral bowing angles, and more proximal fracture height than those in the bowing group. Multivariable analysis showed that the presence of anterolateral bowing itself and height were associated with fracture height in the total cohort. In the subgroup analysis, the lateral bowing angle in the straight group and the estimated apex height in the bowing group were associated with fracture height. The lateral bowing angle was not significantly associated with fracture height in the total cohort and the bowing group. CONCLUSIONS: The presence of anterolateral bowing and the level of the apex of the bowed femur were important factors for the fracture height of AFFs.

Design and finite element analysis of customized pelvic prosthesis / 中国骨伤

OBJECTIVE@#To introduce the design of customized pelvic prosthesis, to evaluate the biomechanical property under three load conditions of customized pelvic prosthesis under three load cinditions.@*METHODS@#A titanium alloy prosthesis for reconstruction of pelvic tumors was designed by CAD software. The strength and stiffness of the custom prosthesis under static and slow gait conditions were analyzed and evaluated by finite element method.@*RESULTS@#The results of the finite element analysis suggested that the maximum von Mises stress in the pelvic under three load conditions were 39.0, 202.8 and 42.4 MPa; the maximum displacement were 0.199, 0.766 and 0.847 mm. The maximum von Mises stress in the prosthesis under three load conditions were 62.3, 318 and 468 MPa. The maximum Von Mises stress in the Ti-alloy prosthesis and pelvic was far smaller than the yield strength of Ti-alloy.@*CONCLUSIONS@#The study can design the size and shape of prosthesis accurately according to patient's condition. The finite element method can reduce the bone stress level and fracture risk, prolong the service life of prostheses, and ensure the safety and stability of the postoperative patients under normal gait.

Three-dimensional finite element analysis of the stress distribution of bone tissue around porous titanium implant / 中华口腔医学杂志

Objective@#To analyze the stress distribution of different types of bone tissue around porous titanium implant in different mechanical loads and to further evaluate the biomechanical properties of porous titanium implant.@*Methods@#Finite element (FE) models of implant restorations for the maxillary first premolar was established, and the diameter of implants in the models was 4.1 mm. Five models was constructed according to diameter of implant central pillar and the thickness of outer porosity: solid group (group A), central pillar 1.5 and 3.1 mm and outer porosity 30% (group B and C), central pillar 1.5 and 3.1 mm and outer porosity 40% (group D and E). Different loads (150 N vertical force, 50 N lateral force) were applied to the occlusal surface of implant restorations in type Ⅲ bone and maximal von Mises stress was evaluated. Meanwhile, a couple of simplified maxillary part models varied in four types of bone were constructed with the implants bearing load of simulation ultimate force to evaluate the stress distribution of different types of bone.@*Results@#With different mechanical loading, the stress value of bone tissue around porous implant (group B-E) was greater than that in the solid structure (group A). Under the load of simulation ultimate force, the maximum stress of the bone rised with the increase of porosity and thickness of the porous implant. And the maximum stress value of the surrounding bone tissue changed with the change of bone. Under vertical loading, the maximal von Mises stress of the bone around solid implants of group A was 17.56 MPa, which was a little lower than that of group B and C. And the maximal equivalent von Mises stress of group D and E was 69.24 MPa. The results of lateral force and simulation ultimate force loading were similar. The stress of the bone tissue around implant increased with the decrease of bone quality. The maximum stress value of group D implant was 134.95 MPa.@*Conclusions@#Porous structure of the implant is conducive to transmit stress to surrounding bone tissue and increases the mechanical stimulation of bone. However, if the value and direction of load are inappropriate or quality of bone is poor, pathological stress may be produced.

Correlation between compression depth and compressive stress of the anteroposterior cervical spinal cord in different sports positions / 中华骨科杂志

Objective@#To explore the relationship between the compression depth and compressive stress of the anterior and posterior cervical spinal cord in different sports positions.@*Methods@#Specimens of ten intact fresh cervical spine (C1-T1) from adult cadaver were collected. In order to simulate cervical disc degeneration and abnormal ligamentum flavum, we placed two hemispherical steel balls into the anterior and posterior side of the cervical spinal cord through the bone window of the C4, 5. The measurement was conducted in 10%, 20%, 30%, 40%, 50%, and 60% of the sagittal diameter for the compressive stress of the anterior and posterior cervical spinal cord under different compression depths of flexion, neutral, and posterior extension.@*Results@#The anterior depth of a certain pressure with the posterior pressure depth was increasing in neutral position, the stress on the anterior of the cervical cord-meningeal complex (CCMC) had no significant change, while the stress on the posterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the posterior of the CCMC varied insignificantly between 10% and 20% depth of canal occlusion (P>0.05). However, there was remarkable significance among 30% and 60% (P<0.05). In extension or flexion position, the stress on the anterior of the CCMC had no significant change, while the stress on the posterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the posterior of the CCMC varied insignificantly between neighboring depths of canal occlusion from 10% (P>0.05). However, there was remarkable significance among 20% and 60% (P<0.05). The posterior depth of a certain pressure with the anterior pressure depth was increasing in neutral position. The stress on the anterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the anterior of the CCMC varied insignificantly between 10% and 20% depth of canal occlusion(P>0.05). However, there was remarkable significance among 30% and 60% (P<0.05). The stress on the posterior of the CCMC had no significant change. In extension or flexion position, the stress on the anterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the anterior of the CCMC varied insignificantly between neighboring depths of canal occlusion from 10% (P>0.05). However, there was remarkable significance among 20% and 60% (P<0.05). The stress on the posterior of the CCMC had no significant change. Compared with the neutral position, the anterior flexion position and the posterior extension position had different trends in the compressive stress in the anterior and posterior aspect of the cervical spinal cord.@*Conclusion@#The stress on the anterior and the posterior of the CCMC has a closely nonlinear relationship with the depth of canal occlusion. With the increase of the depth of canal occlusion, the stress is increasing, especially running over the 30% depress of canal occlusion under neutral position. However, the stress is increased, especially running over the 20% depress of canal occlusion under the flexion and extension position.

Stress distribution in the peri-implant area of pure titanium and titanium-zirconium small implants

Aim: In dental implant treatment, there is a demand for mechanically stronger implants. Despite the existence of several studies showing the clinical success of narrow diameter implants, most of them are based on pure titanium (cpTi) alloys. There is a few clinical evidences of the success rate of titanium-zirconium (TiZr) narrow diameter implants. The aim of this study was to evaluate the stress distribution in the peri-implant area of narrow diameter cpTi and TiZr implants under axial and oblique loads. Methods: Photoelastic models were produced using epoxy resin (PL2, Vishay Precision Group) from a master model. The implants (cpTi and TiZr; Straumann AG) had 3.3 mm in diameter and 12 mm in height. Loads of 100 N and 200 N were applied to the abutment at angles of 0° (axial), 10°, 20°, and 30° (oblique). A circular polariscope (Eikonal) was used under dark field white-light configuration. The isochromatic fringes were analyzed in the peri-implant region in 5 areas, using ASTM table with isochromatic fringes; cervical-mesial, cervical-distal, mid-mesial, mid-distal and apical. Results: In general, under axial and oblique loads, the stress in the TiZr implant was lower than in the cpTi implant. The load of 200 N produced the highest stress values in cpTi and TiZr implants. In both implants and loads, the fringes were located more in apical area at all angles evaluated. Conclusion: It can be concluded that for small implants, the load inclination and intensity change the pattern of stress distribution and the cpTi implant exhibited the highest peri-implant stress

Fracture load and shear stress of prefabricated glass fiber posts

Aim: This study evaluated the fracture load and pattern failure of different prefabricated glass fiber posts (GFPs) of the same diameter. Methods: Seventy-eight (n=13 for six groups) GFPs of 1.6 mm coronal diameter of different brands were evaluated­ Exacto (Angelus), Power Post (BM4), White Post DC (FGM), HiRem (Overfibers), MAQ (Maquira), and SD (Supordont). The posts were subjected to fracture load testing (45° of inclination and 1 mm/min until fracture). Each factor (load (N) and shear stress (MPa)) was analyzed separately using one-way ANOVA followed by the Tukey test (α=0.05). Results: The type of failure was evaluated on a stereomicroscope (×10). The Power Post samples presented higher values of fracture load (p<0.001) followed by Maquira fiber post, White Post , HiRem, Superpost, and the Exacto posts. The failure pattern observed was intralaminar mode II in-plane shear, such as a failure occur parallel to fibers. Conclusion: Despite the same diameter of GFPs, the fracture load and shear resistance were brand-dependent

Relationship between p38 signaling pathway and periodontal ligament fibroblasts secreting inflammatory factors under static pressure / 中国组织工程研究

BACKGROUND: p38 MAPK pathway has been shown to play an important role in the synthesis of inflammatory factors, but the relationship between p38 MAPK signaling pathway and interleukin 17, interleukin 6 and other inflammatory factors in periodontal ligament fibroblasts during orthodontic tooth movement is little reported. OBJECTIVE: To investigate the relationship of the expression of inflammatory cytokines interleukin 17 and interleukin 6 with p38 MAPK in human periodontal ligament fibroblasts under continuous static pressure, and to explore the effect of p38 MAPK signaling pathway on the expression of interleukin 17 and interleukin 6. METHODS: The periodontal tissues of fresh first and second premolars were obtained from the removed teeth of the orthodontic patients aged 11-15 years (informed consent had been obtained). Periodontal ligament fibroblasts were cultured in vitro, and the cell model loaded with gravity was established. Cell culture plates were loaded with 0, 1, 2 and 4 g/cm2 pressure for 5, 15, 30 and 60 minutes, respectively. The expression of p38 MAPK protein was detected. The passage 4 cells were seeded, and then randomized into six groups: blank, dimethyl sulfoxide, inhibitor (p38 MAPK blocker, SB203580), loading, loading plus dimethyl sulfoxide, and loading plus inhibitor groups. The intervention lasted for 60 minutes. The interleukin 17 and interleukin 6 protein and mRNA levels in periodontal ligament fibroblasts after loaded with 4 g/cm2 force were detected by RT-PCR and ELISA. RESULTS and CONCLUSION: (1) The expression level of p38 MAPK protein in the 2 and 4 g/cm2 groups was increased with time prolonged, peaked at 30 minutes, and began to decrease at 60 minutes. (2) Compared with the groups without loading, the loading groups showed an increase in the expression levels of interleukin 17 and interleukin 6. The expression level of interleukin 6 in the inhibitor group was down-regulated, and the expression level of interleukin 17 showed no significant difference. (3) To conclude, static pressure can promote human periodontal ligament fibroblasts to secrete interleukin 17 and interleukin 6. Interleukin 6 secretion may be related to p38 MAPK signaling pathway. However, there is insufficient evidence to demonstrate that p38 MAPK signaling pathway is involved in periodontal ligament fibroblasts inducing interleukin 17 expression under static pressure.

Biomechanical comparison of medial versus lateral sided plating in femoral fractures / Comparação biomecânica de placa óssea medial versus lateral em fraturas do fêmur

ABSTRACT Objective: The aim of the present study was to determine whether the side of application of the plate itself affects the mechanical stability of the fixation. The specific question addressed is whether or not a lateral or medial plate application is biomechanically better, for the treatment of distal diaphysis fractures of the femur. Methods: Stability and stiffness of medial sided plating relative to the conventional lateral sided plating in distal diaphysis of the femur were measured by analyzing axial loading forces leading to implant failure. Sixty synthetic femurs were tested in physiological bending, to calculate the yield and ultimate load to displacement following fixation of distal diaphysis fractures of the femur by either medial or lateral sided plating. Axial loading was applied to samples using a uniaxial testing machine. Results: There was more implant deformation in the lateral sided plating group - a difference with statistical significance. Conclusion: Medial sided plating was found to be as stiff as lateral plating. Medial plating may be a reasonable treatment option that can be used safely in selected cases. Level of Evidence I, Therapeutic Studies Investigating the Results of Treatment

RESUMO Objetivo: O objetivo deste estudo foi determinar se o lado de aplicação da placa em si afeta a estabilidade mecânica da fixação. A questão específica abordada é se a aplicação da placa lateral ou medial é melhor ou não em termos biomecânicos para o tratamento das fraturas da diáfise distal do fêmur. Métodos: A estabilidade e a rigidez da placa medial com relação à lateral, convencional na diáfise distal do fêmur, foram medidas pela análise das forças de carga axial que levam à falha do implante. Sessenta fêmures sintéticos foram testados em flexão fisiológica, para calcular a tolerância e a carga final para o deslocamento após a fixação das fraturas diafisárias distais do fêmur com placa medial ou lateral. A carga axial foi aplicada às amostras usando máquina de teste uniaxial. Resultados: Verificou-se maior deformação do implante no grupo de placa lateral - diferença com significância estatística. Conclusão: Constatou-se que a placa medial era tão rígida quanto a lateral. A placa medial pode ser uma opção de tratamento razoável e segura em casos selecionados. Nível de evidência I, Estudos terapêuticos - Investigação dos resultados do tratamento.

Biophysical characteristics of genipin-crosslinked amniotic membrane bio-scaffold / 中华实验眼科杂志

Objective To investigate the characteristics and feasibility of genipin-crosslinked amniotic membrane(AM) as bio-scaffold.Methods Human umbilical cord mesenchymal stem cells (hUCMSCs) were isolated from fresh umbilical cord and cultured by adherent method.The expressions of PE-CD34,PE-CD45,PE-CD90,FITC-105 and FITC-Oct-4,the markers of hUCMSCs,were detected by flow cytometry.Alizarin red and oil red O staining were performed to identify the cells after adipogenesis and osteogenesis induction on the third-generation cells.Human AMs were treated at 37 ℃ and 45 ℃ by 0.5％ and 1％ genipin solution for 24,36 and 48 hours respectively,and the mechanical properties of AM in each group were measured and compared.The hUCMSCs were divided into only hUCMSCs culture group,fresh AM group,crosslinked AM group,gelatin group and crosslinked AM+gelatin group,and the cells were cultured in the corresponding medium.The content of hydroxyproline among the groups was detected with hydroxyproline kit,and proliferation of the cells (absorbance) was assayed by MTT method to evaluate the biological compatibility of crosslinked AM.Results The maximum tensile displacement of the crosslinked-AM by 0.5％ and 1％ genipin was (8.31±0.43)mm and (4.49±0.37)mm respectively,and those after crosslinked with 0.5％ genipin under the 37 ℃ and 45 ℃ for 24 hours was (9.89±1.09)mm and (5.39±0.59)mm,respectively,showing a significant difference between them (t =6.389,P＜0.05).The maximum tensile displacement of the crosslinked-AM was gradually decreased as the lapse of crosslinking time,and an insignificant difference was found among 24,36 and 48 hours after 0.5％ genipin treatment under the 37 ℃ (P＞0.05).The loading force of the crosslinked-AM was significantly higher in the 1％ genipin treated group than that in the 0.5％ genipin treated group (P＜0.05),and the loading force of the AM was significantly increased in 45 ℃,0.5％ genipin,24 hours crosslinked group compared with the 37 ℃,0.5％ genipin,24 hours crosslinked group (t =5.528,P＜0.05).The content of hydroxyproline in the AM was (1.28±0.36),(2.03 ±0.49) and (2.11 ±0.10) mg/g in the 1％ genipin crosslinked AM group,0.5％ genipin crosslinked AM group and fresh AM group,respectively,and the content of hydroxyproline in the AM in the 1％ genipin group was significantly lower than that in the 0.5％ genipin group in the fresh AM group (both at P＜0.05).The proliferative values of the hUCMSCs were significantly lower in the only hUCMSCs culture group,fresh AM group and gelatin group were significantly reduced in comparison with the crosslinked AM group and crosslinked AM+gelatin group (all at P＜0.05).There was no significant difference in the proliferative values of the hUCMSCs between crosslinked AM group and crosslinked AM+gelatin group (P＞0.05).Conclusions Different crosslinked temprature,crosslinking period and concentration of genipin impact the mechanical properties of AM.Crosslinked AM with genipin is feasible as a carrier scaffold of artificial cornea because of less tissue toxicity and better plasticity.

Can heat-pressed feldspathic ceramic be submitted to multiple heat-pressing?

Abstract The aim of this study was to determine if multiple processing (heat-pressing) of a dental ceramic influences flexural strength, hardness, and microstructure. Ninety bar-shaped specimens (15 mm × 4 mm × 2 mm) of a pressed ceramic (Vita PM9) were fabricated and randomly divided into 6 groups (n = 15) according to the factors "number of pressings" (C1, C2, and C3, fired 1, 2, and 3 times, respectively) and "mechanical cycling" (M). Half of the specimens were mechanically cycled (106 cycles, 45 N, 3.4 Hz, in water) and all specimens were tested for 3-point bending (0.5 mm/min, load 1000 kgf) and Vickers hardness (19.6 N for 20 s). X-ray diffraction was used to characterize the phases and scanning electron microscopy to characterize the microstructure. The flexural strength data was statistically analyzed with Weibull analysis, ANOVA, and Tukey test. Hardness data was evaluated by 2-way ANOVA and Fisher test. All tests were performed with a significance level of 0.05. Two-way ANOVA revealed that neither "number of pressings" (p=0.085) or "mechanical cycling" (0.055) significantly affected flexural strength. But Weibull analysis showed significant difference for Weibull moduli and characteristic strength between groups. For hardness, a statistical difference was seen for the interaction "Number of pressings * Mechanical cycling", (p = 0.016). Hardness decreased in the following order: C1 (775±17.2), CM3 (751±101), CM2 (735±45), C3 (701±82), CM1 (671±82), and C2 (663±92). Fewer defects were observed with an increased number of firings. Therefore, the possibility of recycling PM9 ceramic does not interfere in the evaluated mechanical properties and improves microstructure.

Self-designed adjustable tibial weight-bearing brace for AO type 42-B tibial shaft fractures / 中华创伤骨科杂志

Objective To investigate the clinical efficacy of our self-designed adjustable weight-bearing brace for AO type B tibial shaft fractures managed by interlocking intramedullary nail.Methods A total of 68 consecutive patients with AO type 42-B tibial shaft fracture who had been managed from April 2013 to March 2015 hy interlocking intramedul]ary nail were recruited into our study.They were randomized into 2 equal groups (n =34).Group A received conventional therapy after operation while group B received auxiliary mauagement with our self-designed adjustable weight-bearing brace after conventional postoperative therapy for one week.The 2 groups were compared at postoperative 1,3 and 6 months and at the final follow-up in terms of visual analogue scale (VAS),weight-bearing status of the affected limb,time for fracture union,Radiographic Union Score for Tibial Fractures (RUST) and Johner-Wruhs scale.Results Of this series,62 cases were followed up for 12 to 18 months (average,14.7 months),5 ones were lost to the follow-up and one withdrew.The mean VAS scores at 3-month and 6-month follow-ups for group B were 2.5 ± 0.8 and 0.9 ± 0.6 respectively,significantly lower than those for group A (3.0 ± 0.9 and 1.4 ± 0.8 respectively) (P ＜ 0.05).In group A at 1-month,3-month and 6-month follow-ups,the weight-bearing status was 44.1％ ± 17.5％,72.0％ ±17.4％ and 86.4％ ±12.5％ while the mean RUST scores were 5.4±1.4,8.7±1.1 and 10.3 ± 1.1,respectively.In group B at 1-month,3-month and 6-month follow-ups,the weight-bearing status was 53.8％ ± 11.0％,84.1％ ± 12.2％ and 94.4％ ± 10.6％ while the mean RUST scores were 6.5 ± 0.8,9.9 ± 0.9 and 11.3 ± 0.8,respectively.There were significant differences between the 2 groups in the above indexes (all P ＜ 0.05).Group B achieved clinical fracture union after an average of 3.3 ±0.7 months,significantly faster than group A (3.9 ± 1.0 months) (P ＜ 0.05).According to the Johner-Wruhs scoring,group A had 19 excellent cases and 12 good ones while group B had 27 excellent ones and 4 good ones,showing a significant difference between the 2 groups (P ＜ 0.05).Conclusions Early application of our self-designed adjustable weight-bearing brace for patients with AO type B tibial shaft fracture managed by interlocking intramedullary nail can reduce postoperative pain,accelerate callus growth,shorten bony healing time and achieve satisfactory functional recovery.

Finite element analysis of stress of the adjacent vertebral end plate of T12vertebral body in different compression states / 中国组织工程研究

BACKGROUND:Vertebral compression fractures are the most common vertebral fractures in the elderly patients with osteoporosis, and the correlation between the compression of anterior border of vertebral body and adjacent vertebral refractures is not clear. OBJECTIVE:To establish a model of different compression of T12vertebral body with finite element method, and analyze the relationship between the compression of T12vertebral body and the stress of adjacent vertebral plate. METHODS:Based on thoracolumbar CT data of normal adult volunteers, MIMICS/3-matic was imported. Through image segmentation, repair and three-dimensional mesh of accessto thoracic and lumbar T11-L1data, grid assigned material properties was imported to ABAQUS so as to establish ligament, joint and other small features and obtain realistic three-dimensional finite element model. The six degrees of freedom, including anteflexion, posterior extension, left and right flexion, left and right rotation, were loaded, to verify the validity of the normal model. With the frontier of vertebral body compression to 90%, 80%, 70%…10% of the nine states, MISES stressesof the T11andL1segment intervertebral disc endplate were extracted; the relationship curve of compression state and endplate stress was obtained. RESULTS AND CONCLUSION:(1) The model was highly realistic and could reflect the actual stress state. (2) The stress value of T11vertebral body and L1vertebral body was positively correlated with the compression of T12vertebral body. Increased stress may lead to an increased likelihood of end plate fractures, which increases the risk of fractures in the adjacent vertebralbodies.

Efeito de duas técnicas de gradação da zircônia no limite de fadiga de próteses parciais fixas monolíticas de três elementos / Effect of two grading zirconia techniques on the fatigue limit of fullcontour 3-unit fixed dental prothesis

O objetivo deste estudo foi avaliar os efeitos de duas técnicas de gradação da zircônia no limite de fadiga de próteses parciais fixas (PPFs) de 03 elementos. Blocos pré-sinterizados de 3Y-TZP (zircônia policristalina parcialmente estabilizada por 3% mol de ítria) foram fresados para obter 69 PPFs, que foram divididas em 3 grupos (n = 23). O grupo controle (CTL) foi sinterizado e glazeado odedecendo os parâmetros usuais. Nos dois grupos experimentais as PPFs receberam sílica/vidro antes da sinterização. O grupo sílica sol-gel (SSG) foi graduado pela rota de processamento sol-gel, enquanto o grupo vidro-zircônia-vidro (GZG) foi graduado pela técnica de suspensão (slurry). Os grupos graduados não receberam a camada de glaze após a sinterização. Todas as PPFs foram cimentadas nos pilares de compósito com cimento resinoso de dupla polimerização, incluídas em poliuretano e armazenadas em água por cinco dias. A carga inicial do teste de fadiga foi calculada com base nos resultados do ensaio monotônico de três amostras de cada grupo. Para determinar o limite de fadiga 20 amostras de cada grupo foram submetidas ao método da escada ou staircase (100.000 ciclos/5 Hz). Os limites de fadiga (em Newton) foram: CTL = 1607,27; SSG = 1824,31; GZG = 2006,57 e o teste de Dixon e Mood indicou diferença estatística entre os grupos (intervalo de confiança de 95%). As infiltrações de sílica e vidro no corpo da zircônia, por dois diferentes métodos de gradação, aumentaram o limite de fadiga de PPFs em zircônia monolítica(AU)

The aim of this study was to evaluate the effects of two grading zirconia techniques on the fatigue limit of 3-unit fixed dental prostheses (FDPs). Presintered blocks of 3YTZP (3 mol% yttria-stabilized tetragonal zirconia polycrystal) were milled to obtain sixty-nine 3-unit FDPs, which were divided into three groups (n = 23). The control group (CTL) was sintered and glazed following the usual parameters. In the two experimental groups presintered FDPs received silica/glass before sintering. Silica sol-gel group (SSG) was graded by the sol-gel processing route, while the glasszirconia-glass group (GZG) was graded by a slurry technique. Graded groups did not receive a glaze layer after sintering. All FDPs were then luted with a dual-curing resin cement on composite abutments, embedded in polyurethane and stored in water for five days. The initial load of the fatigue test was calculated based on the results of the monotonic testing applied on three specimens of each group. To determine the fatigue limit, 20 samples of each group were subjected to staircase testing (100,000 cycles/5 Hz). The fatigue limits (in Newtons) were CT = 1607.27, SSG = 1824.31, and GZG = 2006.57, and the Dixon and Mood test indicated statistically significant differences among groups (95% confidence interval). The infiltration of silica and glass on zirconia bulk, by two different grading methods, increased the fatigue limits of monolithic zirconia FDPs(AU)