Biomechanical Effects of Angiotensin 1-7 in Diabetes Rats Femur / Efectos Biomecánicos de la Angiotensina 1-7 en el Fémur de Ratas Diabéticas

SUMMARY: It is known that diabetes mellitus has late complications, including microvascular and macrovascular diseases. Diabetes can affect bones through biochemical markers of bone structure, density, and turnover. This study aimed to biomechanically investigate the bone-protective effects of angiotensin 1-7 (Ang 1-7), one of the active peptides in the renin-angiotensin system, in rats with diabetes. Thirty male Wistar albino rats, three months old and weighing 250-300 g, were divided into four groups: diabetes, Ang 1- 7, diabetes plus Ang 1-7, and control. One month later, diabetes developed in rats; the rats were sacrificed, and their right femur was removed. Three-point bending biomechanical tests were performed on the femurs. The diabetic group had significantly higher bone fragility than the other groups (Pr >.05). Bone fragility was lower, and bone flexibility was higher in the Ang 1-7 groups (Pr>F value 0.05). As a result of our study, the effect of Ang 1-7 on the bones of rats with diabetes was investigated biomechanically. Ang 1-7 has a protective impact on the bones of rats with diabetes.

Se sabe que la diabetes mellitus tiene complicaciones tardías, incluyendo enfermedades microvasculares y macrovasculares. La diabetes puede afectar los huesos a través de los marcadores bioquímicos de la estructura, la densidad y el recambio óseo. Este estudio tuvo como objetivo investigar biomecánicamente los efectos protectores en los huesos de la angiotensina 1-7 (Ang 1-7), uno de los péptidos activos en el sistema renina-angiotensina, en ratas con diabetes. Treinta ratas albinas Wistar macho, de tres meses de edad y con un peso de 250-300 g, se dividieron en cuatro grupos: diabetes, Ang 1-7, diabetes más Ang 1-7 y control. Un mes después, se desarrolló diabetes en ratas; se sacrificaron los animales y se extrajo su fémur derecho. Se realizaron pruebas biomecánicas de flexión de tres puntos en los fémures. El grupo diabéticos tenía una fragilidad ósea significativamente mayor que los otros grupos (Pr > 0,05). La fragilidad ósea fue menor y la flexibilidad ósea fue mayor en los grupos Ang 1-7 (valor Pr>F 0,05). Como resultado de nuestro estudio, se determinó biomecánicamente el efecto de Ang 1-7 en los huesos de ratas con diabetes. Se concluye que Ang 1-7 tiene un impacto protector en los huesos de ratas diabéticas.

Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique

PURPOSE: The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS: Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS: Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION: Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

Influence of different surface treatments on bond strength of novel CAD/CAM restorative materials to resin cement

PURPOSE: To evaluate the effects of different surface treatments on the bond strength of novel CAD/CAM restorative materials to resin cement by four point bending test. MATERIALS AND METHODS: The CAD/CAM materials under investigation were e.max CAD, Mark II, Lava Ultimate, and Enamic. A total of 400 bar specimens (4×1.2×12 mm) (n=10) milled from the CAD/CAM blocks underwent various pretreatments (no pretreatment (C), hydrofluoric acid (A), hydrofluoric acid + universal adhesive (Scotchbond) (AS), sandblasting (Sb), and sandblasting + universal adhesive (SbS)). The bars were luted end-to-end on the prepared surfaces with a dual curing adhesive resin cement (Variolink N, Ivoclar Vivadent) on the custom-made stainless steel mold. Ten test specimens for each treatment and material combination were performed with four point bending test method. Data were analyzed using ANOVA and Tukey's test. RESULTS: The surface treatment and type of CAD/CAM restorative material showed a significant effect on the four point bending strength (FPBS) (P < .001). For LDC, AS surface treatment showed the highest FPBS results (100.31 ± 10.7 MPa) and the lowest values were obtained in RNC (23.63 ± 9.0 MPa) for control group. SEM analyses showed that the surface topography of CAD/CAM restorative materials was modified after treatments. CONCLUSION: The surface treatment of sandblasting or HF acid etching in combination with a universal adhesive containing MDP can be suggested for the adhesive cementation of the novel CAD/CAM restorative materials.

Estudo biomecânico comparativo da resistência de segmentos ósseos de rádios de cães autoclavados ou desvitalizados em nitrogênio líquido / Biomechanical comparative study of the strength of bone segments from the radius of dogs autoclaved and devitalized in liquid nitrogen

O presente estudo comparou, por meio do ensaio de flexão em quatro pontos, a resistência de segmentos de rádios de cães autoclavados e desvitalizados em nitrogênio líquido. Avaliaram-se 40 rádios, que foram divididos em quatro grupos: grupo autoclave (GA), grupo controle autoclave (GCA), grupo nitrogênio (GN) e grupo controle nitrogênio (GCN). Os corpos de prova dos grupos GCA e GCN pertenciam ao lado contralateral dos grupos GA e GN, respectivamente. Os ossos foram autoclavados a 121°C, por 20min a 2atm. A desvitalização em nitrogênio foi realizada por meio da imersão em nitrogênio líquido, por 20min, seguida de descongelamento à temperatura ambiente, sendo finalizada por imersão em solução de NaCL a 0,9%, por mais 15min. Após os testes biomecânicos, foram comparadas as variáveis força máxima, rigidez, altura máxima à secção transversa do corpo de prova, deslocamento do baricentro em relação ao eixo x, flecha, tensão-tração, tensão-compressão e tensão máxima. Não foram encontradas diferenças estatisticamente significantes entre os grupos GN e GCN. Foram encontradas diferenças estatisticamente significantes entre os grupos GA e GCA somente na comparação da variável força máxima. A análise das variáveis tensão-tração, tensão-compressão e tensão máxima evidenciou diferenças estatisticamente significantes entre os grupos GA e GN, sendo os valores maiores para o grupo GA. Também foi realizada comparação entre os deltas (GN menos GCN e GA menos GCA), em que não foram observadas diferenças estatísticas.(AU)

The study compared through the four points bending test, the strength of bone segments autoclaved and devitalized in liquid nitrogen radius segments. 40 radius were used, collected and divided into 4 groups, as follows: Autoclave Group (GA), Control Autoclave Group (GCA), Nitrogen Group (NG) and Control Nitrogen Group (GCN). Bone segments from groups GCA and GCN were contralateral to GA and NG. The segments were autoclaved at 121ºC and 2 atm for 20 minutes. Nitrogen devitalization of the bone segments was obtained by 20 minutes immersion, followed by thawing at room temperature and 15 minutes immersion in 0.9% NaCL solution. After biomechanical tests the variables compared were maximum strength, stiffness, maximum hight trough the transverse section of the bone segment, centers of mass dislocation in relation to x axe, arrow, stress-tension, stress-compression and maximum stress. No statistically significant differences between the GN and GCN groups were found. Statistically significant differences were found between GA and GCA groups only in the comparison of the maximum force variable. The analysis of variable stress-tension, stress-compression and maximum stress showed statistically significant differences between the GA and GN groups, with higher values for the GA group. Comparison of the deltas (GN least GCN and GA least GCA) where no statistical differences were observed was also performed.(AU)

Forças, momentos e coeficiente de atrito em teste de três pontos e em teste de resistência ao deslizamento com braquetes autoligáveis e fios 0.014" utilizando um novo dispositivo / Forces, moments and coefficient of friction in three-bracket bending test and in resistance to sliding test with self-ligating brackets and wires 0.014'' using a new device

O objetivo principal do estudo é comparar o teste em 3 pontos com braquetes com o teste de resistência ao deslizamento utilizando um novo dispositivo que realiza a mensuração simultânea do coeficiente de atrito, das forças e dos momentos nos braquetes de ancoragem e da força de desativação no braquete desalinhado, exercidos por fios ortodônticos. Os objetivos secundários foram desenvolver o dispositivo e comparar, no teste em 3 pontos: (i) a influência, nas grandezas e no coeficiente de atrito cinético, da variação da simetria nas distâncias inter-braquetes, do tipo de braquete de ancoragem (canino ou 2º pré-molar), do deslocamento (3 ou 5mm) do braquete central, do sentido do desalinhamento (vestibular ou lingual) do braquete central e da marca de fio-braquete; (ii) as 3 formas de cálculo do coeficiente de atrito cinético; (iii) os 10 ciclos, para vestibular ou lingual, para verificar se eles são semelhantes ou não entre si. Foram utilizados braquetes autoligáveis (dentes 13, 14 e 15) e fios 0.014'' NiTi e CuNiTi das marcas Aditek e Ormco. O teste de resistência ao deslizamento foi realizado no desalinhamento lingual, nos dois deslocamentos e na configuração simétrica. O teste em 3 pontos com braquetes foi realizado no desalinhamento lingual e vestibular, nos dois deslocamentos e na configuração simétrica e assimétrica. Por meio da ANOVA, foram comparados, entre os dois tipos de teste: (A) as grandezas e o coeficiente de atrito e (B) o coeficiente de atrito gerado apenas no braquete de 2º pré-molar. Utilizando-se do mesmo teste estatístico foram comparados, no teste em 3 pontos com braquetes: (A) na configuração...

The main objective of the study is to compare the three-bracket bending test with the resistance to sliding test using a new device that performs simultaneous measurement of coefficient of friction, the forces and moments on the anchor brackets and deactivation force in misaligned bracket, exercised by orthodontic wires. Secondary objectives were to develop the device and compare, in the three-bracket bending test: (i) the influence, on the physical quantities and on the kinetic friction coefficient, of the variation of the symmetry in the inter-bracket distance, of the type of anchor bracket (canine or 2nd premolar), of displacement (3 or 5mm) and misalignment (buccal or lingual) of the central bracket, and of the wire and bracket brand; (ii) the three ways to calculate the coefficient of kinetic friction; (iii) the 10 cycles, for buccal or lingual, to see if they are similar or not. Self-ligating brackets were used (teeth 13, 14 and 15) and wires 0.014 '' NiTi and CuNiTi of Aditek and Ormco brands. The resistance to sliding test was conducted on the lingual misalignment, on both displacements and on symmetrical configuration. The three-bracket bending test was held at the lingual and vestibular misalignment, at both displacements and at the symmetrical and asymmetrical configuration. Through ANOVA, were compared, between the two types of tests: (A) the quantities and the coefficient of friction and (B) the coefficient of friction generated only in the second premolar bracket. Using the same statistical test were compared, in three-bracket bending test: (A) in symmetrical configuration, the quantities and the coefficient of friction arising from the variation in the wire and bracket brands, displacement, misalignment and the type of bracket; (B) the quantities...

Comparison of flexural strength and modulus of elasticity in several resinous teeth splinting materials

PURPOSE: Direct splinting material should have high flexural strength to withstand force during mastication and low modulus of elasticity to provide some movement while force applied for relief of stress. The purpose of this study was to compare flexural strength and modulus of elasticity of several resinous splinting materials. MATERIALS AND METHODS: Four materials; Super-Bond C&B, G-FIX, G-aenial Universal Flo, FiltekTM Z350 XT; were used in this study. Fifteen rectangular bar specimens of each material were prepared. Three-point bending test were performed to determine physical properties. Maximum load at fracture was recorded and flexural strength and modulus of elasticity were calculated. One-way analysis of variance (ANOVA) and Scheffe's tests at a 0.05 level of significance were conducted on all test results. RESULTS: Statistical analysis reveals that Super-Bond C&B had significant low mean value for flexible strength and the other three materials showed no significant difference. For modulus of elasticity, Super-Bond C&B exhibited statistically lower modulus of elasticity. G-FIX presented intermediate result, showing statistically higher modulus of elasticity than Super-Bond C&B but lower than G-aenial Universal Flo and FiltekTM Z350 XT. There was no significant difference on modulus of elasticity between G-aenial Universal Flo and FiltekTM Z350 XT. CONCLUSION: Using a G-FIX, the newly commercially available splinting material, which shows higher fracture resistance properties comparable to flowable and restorative composite resin and a relatively flexible nature might be a beneficial for stabilizing teeth mobility.

Comparative study on bond strength of porcelain fused to CAD/CAM and to cast pure titanium / 实用口腔医学杂志

Objective:To compare the titanium-porcelain bonding strength between CAD/CAM and cast pure titanium.Methods:Pure titanium samples were prepaired by CAD/CAMand casting respectively and fused with porcelain.The bond strength between tita-nium and porcelain of the samples was measured with three-point test.The titanium-porcelain interface was investigated under scanning electronic microscope(SEM).Results:The bond strength of CAD/CAMpure titanium to porcelain was (35.95 ±3.74)MPa and cast pure titanium to porcelain was (28.37 ±1 .98)MPa(P <0.05).SEMobservation showed that there was thin transition layer between titanium substrate and ceramic in CAD/CAM bond interface,titanium and porcelain combined closely,no obvious pores.However, there was thicker transition layer and small pore in cast pure titanium to porcelain bonding interface.Conclusion:The bonding strength of porcelain to CAD/CAMpure titanium is greater than that of porcelain to casting pure titanium.

A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy

PURPOSE: The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS: Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (alpha=.05). RESULTS: The 3-point bending test showed the strongest (40.42 +/- 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 +/- 2.46 MPa), precious metal alloy containing 83% of gold (35.89 +/- 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 +/- 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION: The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa).

Construction and identification of humerus three-dimensional finite element model in children / 中国组织工程研究

BACKGROUND:Mechanical experiment of finite element numerical simulation is the effective method to research the biomechanical structure of human body. OBJECTIVE:To establish the three-dimensional finite element model of a normal 6-year-old child’s humerus. METHODS:CT images of a 6-year-old child volunteer were imported to the Mimics 10.01 software. The threshold segmentation method was used to rebuild the humerus three-dimensional model. The surface optimization treatment and surface patches dicision were performed on the surface of the model with Geomagic Studio 12.0 software. Then the mesh generation was completed in the software TrueGrid. Final y, the material properties were set and the finite element model was completed. The boundary conditions and constrains were exerted to simulate the three-point-bending test of humeurs. After the simulation, the results were outputted. RESULTS AND CONCLUSION:The humerus finite element model included 3 024 nodes and 18 758 nodes-hexahedron elements. The 0.01 m/s and 3 m/s dynamic loads were loaded respectively, then the central humerus fracture occurred and the load-displacement curve was close to the cadaver test results. The simulation results show that the simulation results of children humerus finite element model are close to the cadaver’s test, and the finite element simulation method can simulate the physical properties of the human skeleton very wel .

Influence of fluoride-containing acidic artificial saliva on the mechanical properties of Nickel-Titanium orthodontics wires.

Objective: This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. Design: A prospective laboratory investigation. Setting: Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. Materials and Methods: Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM). Results: A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. Conclusions: The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.

Effect of fluoride mouth rinses on various orthodontic archwire alloys tested by modified bending test: An in vitro study.

Objective: Fluorides can cause corrosion and degradation in mechanical properties of commonly used archwires by forming hydrofluoric acid HF and causing disruption of protective titanium oxide layer. Hence, the aim of this study was to assess the change in load deflection characteristics of Ni-Ti, Cu Ni-Ti, S.S, and β-Ti wires on immersing in fluoride mouth rinses of two types- Phosflur and neutral NaF mouth rinse utilizing a modified bending test and comparing it to control. Materials and Methods: Round preformed wires were immersed in 10 ml of control and test solution (Phosflur and S-Flo mouth rinse) for 1.5 hours and incubated at 37°C. Modified bending test was carried out to evaluate load-deflection characteristics of different wires using Instron. Analysis of variance (ANOVA) was applied to determine if statistically significant difference exist among the mean load values obtained at various deflections in control and test solutions. Results: There was no statistically significant reduction in load deflection characteristics of Ni-Ti, copper Ni-Ti, β-Ti, and S.S wires on immersing in Phosflur mouth rinse and neutral sodium fluoride mouth rinses as compared to control at 2.5 and 1 mm of deflection in unloading phase. Conclusion: Phosflur and a neutral sodium fluoride mouth rinse did not affect the mechanical bending properties of Ni-Ti, copper Ni-Ti, B-Ti, and SS wires in in vitro conditions.

Effect of Incremental Exercise on the of Maximum Force of Femur and Lumbar Vertebrae in SD Rats / 中国运动医学杂志

Objective The aim of the study is to investigate whether the progressive incremental exercise can induce the change in bone maximum force.Methods One hundred and seventy healthy SD rats,aged 3 months,were used as samples after adaptive exercise for one week,and then they were divided to a basic control group(C_0),8 control groups and 8 exercise groups according to the training duration(2W,4W,6W,8W,9W,11W,13W and 15W).Based on Bedford and our pre-study.the longest training duration of the rats was 15 weeks.The maximum force(F) of femoral bone and the 2nd lumbar vertebrae(L_2)were tested by three-point bending test and compressive test separately.Results It was shown that there was no pronounced difference in F of femoral bone between con trol groups and exercise groups.But significant differences in F of L_2 were found between the control groups and exercise groups(P<0.001).Conclusions Changes in different degree were found in the F of femoral bone and L_2 during the process of growth.The differential effects of incremental exercise on F were caused by the difference in training intensities and in the bone types.

The fracture resistance of heat pressed ceramics with wire reinforcement / 대한치과보철학회지

STATEMENT OF PROBLEM: Ceramics have been important materials for the restoration of teeth. The demands of patients for tooth-colored restorations and the availability of various dental ceramics has driven the increased use of new types of dental ceramic materials. Improved physical properties of theses materials have expanded its use even in posterior crowns and fixed partial dentures. However, ceramic still has limitation such as low loading capability. This is critical for long-span bridge, because bridge is more subject to tensile force. PURPOSE: The wire reinforced ceramic was designed to increase the fracture resistance of ceramic restoration. The purpose of this study was to evaluate the fracture resistance of wire reinforced ceramic. MATERIAL AND METHODS: Heat pressed ceramic (ingot No.200 : IPS Empress 2, Ivoclar Vivadent, Liechtenstein) and Ni-Cr wire (Alfa Aesar, Johnson Matthey Company, USA) of 0.41 mm diameter were used in this study. Five groups of twelve uniform sized ceramic specimens (width 4 mm, thickness 2 mm, length 15 mm) were fabricated. Each group had different wire arrangement. Wireless ceramic was used as control group. The experimental groups were divided according to wire number and position. One, two and three strands of wires were positioned on the longitudinal axis of specimen. In another experimental group, three strands of wires positioned on the longitudinal axis and five strands of wires positioned on the transverse axis. Three-point bending test was done with universal testing machine (Z020, Zwick, Germany) to compare the flexural modulus, flexural strength, strain at fracture and fracture toughness of each group. Fractured ceramic specimens were cross-sectioned with caborundum disc and grinded with sandpaper to observe interface between ceramic and Ni-Cr wire. The interface between ceramic and Ni-Cr wire was analyzed with scanning electron microscope (JSM-6360, JEOL, Japan) under platinum coating. RESULTS: The results obtained were as follows: 1. The average and standard deviation in flexural modulus, flexural strength and fracture toughness showed no statistical differences between control and experimental groups. However, strain was significantly increased in wire inserted ceramics (P < .001). 2. Control group showed wedge fracture aspects across specimen, while experimental groups showed cracks across specimen. 3. Scanning electron microscopic image of cross-sectioned and longitudinally-sectioned specimens showed no gap at the interface between ceramic and Ni-Cr wire. CONCLUSION: The results of this study showed that wire inserted ceramics have a high strain characteristic. However, wire inserted ceramics was not enough to use at posterior area of mouth in relation to flexural modulus and flexural strength. Therefore, we need further studies.

Idiopathic Scoliosis in Korean Middle School Students: Prevalence study / 대한정형외과학회잡지

PURPOSE: To update and reevaluate the scoliosis prevalence in middle school students in Korea, and correlate those data with past references and other countries general prevalence. MATERIALS AND METHODS: Among the middle schools in Seoul city, forty-five middle schools were randomly selected for screening. Total number of students were 46,428 who were screened for the prevalence of adolescent idiopathic scoliosis. There were 24,892 boys and 21,536 girls. Their age ranged from 12 to 15 years. Adams forward bending test and "Scoliometer" (Orthopaedic Systems, Inc, USA) were used to detect and measure the degree of rotation of trunk. Students more than 5 (ATR were assessed subsequently by standardized clinical and radiological examinations. RESULTS: Using 10 degrees as cut-off points, 465 students were found to have structural idiopathic scoliosis, representing a prevalence of 0.9% overall. CONCLUSION: The prevalence of the scoliosis has not changed from previously estimated rates in Korea, which was about 20 years ago. It nearly approximates with the prevalence of the world wide reported. We also confirmed that it is not necessary to issue a mass screening, considering the cost and effectiveness aspect, due to its low prevalence.