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Objective By comparing the fatigue strength of type A and type B locking compression plates (LCP) in distal femoral plate, a theoretical evaluation method was provided for type selection of bone plate when testing its bending strength and fatigue performance. Methods Through bending strength performance test and fatigue performance test on bone plates with different types, combined with ANSYS Workbench, the finite element analysis on total deformation, von Mises stress and fatigue service life of bone plates were conducted. Results The fatigue strength of type A plate was 30.7% higher than that of type B plate, the stress of type A plate was lower than that of type B plate, and the minimum fatigue service life of type A plate was 17% higher than that of type B plate. Conclusions The fatigue performance of type A plate is better than that of type B plate, so the failure possibility of type A plate was lower than that of type B plate.The results provide references for assisting selection of different bone plates when testing the performance of two newly developed bone plates.
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Objective@#To investigate the antibacterial properties, biocompatibility and mechanical properties of Cu-ZnO-loaded dental veneering porcelain to provide an experimental basis for the development of new dental veneering porcelain. @*Methods@#Cu-ZnO nanoparticles were added to IPS E.max Ceram for restorative veneer porcelain at different mass percentages of 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, and 6 wt% using ball milling in ceramic powder. A cylindrical specimen with a diameter of 20 mm and a thickness of 2 mm was prepared by high-temperature sintering. Scanning electron microscopy was used to observe the surface morphologies of nano-Cu-ZnO and the specimens. The antibacterial effect of Escherichia coli (E. coli) was quantitatively studied by the plate colony counting method. The CCK-8 method was used to evaluate in vitro the cytotoxicity of the tested piece to mouse fibroblasts (L929). Live and dead cells were observed by fluorescence microscopy. The mechanical properties of modified IPS E. Max Ceram veneering porcelain were tested by a three-point bending strength test. @* Results @# Under the scanning electron microscope, Cu-ZnO appears with a block-like structure and can be seen dispersed in the veneering porcelain. When the nano Cu-ZnO loading was 1 wt%, 2 wt%, 3 wt%, and 4 wt%, the antibacterial rates of the specimens were 24.85%, 67.94%, 96.92%, and 99.99%, respectively, and the difference between the experimental groups and the control group was statistically significant (F = 23.308,P = 0.001). The relative growth rate of each group was greater than 80% after coculture with mouse fibroblast cells (L929) for 1 day and 3 days, and there was no significant difference between the groups. The morphology of L929 cells was normal after coculture for 24 hours. With the increase in the Cu-ZnO concentration, the flexural strength of the specimen exhibited an increasing trend followed by a decreasing trend. The bending strength of the specimen loaded with 3 wt% nano Cu-ZnO reached the maximum value (84.728 ± 6.82) MPa, and there was no statistically significant difference between groups (F = 0.633,P = 0.702).@*Conclusion@#The antibacterial rate of IPS E. max Ceram veneering porcelain loaded with 3 wt% nano Cu-ZnO was more than 96% against E. coli after high-temperature sintering at 750 ℃. The bending strength reached the maximum (84.728 ± 6.82) MPa, and there was no obvious cytotoxicity.
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BACKGROUND: Studies have shown that the nano-hydroxyapatite coating on the surface of zirconia has not only high strength and toughness, but also good biocompatibility. It is an ideal substitute for hard tissue. However, the coating is easy to fall off from the surface of zirconia, which is a fatal defect. OBJECTIVE: To prepare functionally graded bioceramics with pure zirconia as matrix, gradient layer in the middle and nano-hydroxyapatite on the surface by gradient composite technology and to screen the optimal mechanical properties and sintering temperature. METHODS: Using zirconia and nano hydroxyapatite powder as raw materials, ceramic specimens were prepared by the lamination method in powder metallurgy. According to the thickness of zirconia layer, three groups A (40 mm), B (30 mm) and C (20 mm) were designated. Each group was sub-divided into three subgroups 1 (3 layers), 2 (5 layers) and 3 (7 layers). Thus, there were 162 ceramic specimens in nine subgroups. The ceramic specimens were sintered at different temperatures (1 300,1 350,1 400,1 450,1500, and 1 550°C) and then processed into rectangular specimens for mechanical property testing. RESULTS AND CONCLUSION: The zirconia-based nano-hydroxyapatite functionally graded material can be formed by 10 MPa single side vertical pressure. With the increases in the number of gradient layers and sintering temperature, the mechanical properties of the functionally graded bioceremics in each group were enhanced. The functionally graded bioceramics had the optimal mechanical properties when sintering temperature was 1 550°C, the number of gradient layers was 7, and substrate thickness was 40 mm. The optimal mechanical property of the functionally graded bioceramics produced at above parameter was significantly superior to that produced at other eight sets of parameters (P<0.05). According to the optimal gradient design, the zirconia-based nano-hydroxyapatite functionally graded ceramic specimens prepared by high temperature sintering technique have stronger mechanical properties.
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OBJECTIVE@#To evaluate the effect of sandblasting or acid etching on the three-point bending strength to the modified polyetheretherketone (PEEK).@*METHODS@#Forty-eight bars (15 mm×2 mm×1 mm) of specimens were fabricated from the modified PEEK (BioHPP). They were randomly divided into the following groups: A, B, C and D groups, which were blasted with alumina particles; E, F, and G groups, which were etched with 98% concentrated sulfuric acid; and control group H. The sand blast pressure of groups A, B and C was 0.2 MPa, and the grain sizes of the sand blasted were 120, 50, and 250 µm, respectively. Group D was blasted with 120 µm particle size at 0.7 MPa pressure. Groups E, F and G were acid etched for 60, 120, and 300 s, respectively. No surface treatment was conducted in group H. After all the specimens were processed, one sample was randomly selected from each group to observe its surface morphology under a scanning electron microscope (SEM), and the other specimens were tested for their three-point bending strength. SPSS 22.0 software was used to analyze the experimental data and to test whether the difference was statistically significant.@*RESULTS@#SEM observation showed that the surface morphology of the specimen changed after the treatment and revealed different degrees of cracks, pits, or voids. The three-point bending test indicated that the strength of the specimens treated with sandblasting or concentrated sulfuric acid decreased compared with that of the control group (P0.05). The strength of group D was lower than that of group A at the same particle size (P0.05).@*CONCLUSIONS@#The bending strength of BioHPP could be significantly decreased by surface sand blasting or concentrated sulfate etching as the sandblasting pressure increased, but the bending strength did not decrease as sand particle size and acid etching time changed.
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Dental Bonding , Ketones , Materials Testing , Microscopy, Electron, Scanning , Polyethylene Glycols , Resin Cements , Shear Strength , Surface PropertiesABSTRACT
Objective@#To evaluate the effect of sandblasting on bending strength and subcritical crack growth (SCG) under cyclic loading of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics.@*Methods@#After being polished, sixty bar-shaped specimens of Y-TZP (Wieland zirconia ceramics) were assigned to two groups (n=30) according to the random number table, the sandblasting group (SG) which was treated with sandblasting and the control group (CG) which remained untouched. In each group, half of the specimens (n=15) were subjected to bending strength test, and the results were examined by Weibull statistics and analyzed with ANOVA. The other 15 specimens in each group were subjected to fatigue tests. The results were examined by Weibull statistics and subcritical crack propagation rates were calculated.@*Results@#The bending strengths of SG and CG were (1 291±133) and (1 140±124) MPa (F=10.117, P=0.004), and the Weibull modules of the two groups were 11.06 and 10.64 respectively. The crack growth rate of SCG of SG was lower than that of CG under the same cyclic loading.@*Conclusions@#Proper sandblasting on Y-TZP ceramic can increase its bending strength and resistance to SCG.
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Objective To compare the influence of resin core on overall bending strength of fiber post-core restoration.Methods 60 mandibular first premolar extracted because of orthodontic treatment was selected.3M light -cured composite resin P60,medental dual-cured resin,pulpdent dual-cured resin combined with viva carbon fiber reinforced glass fiber post were applied.The changes of teeth in vitro were observed when strength was given on.Results The flexural strength of 3M light-cured composite resin was (80.182 ±9.512)N,Medental dual-cured resin was (87.805 ± 11.649) N,Pulpdent dual-cured resin was (85.458 ± 10.845) N.The flexural strength of 3 M light-cured composite resin was lower than that of medental dual-cured resin and pulpdent dual-cured resin (t =5.758,3.084,both P ＜ 0.05).There was no statistical differences of flexural strength between medental dual-cured resin and pulpdent dual-cured resin(t =0.718,P ＞ 0.05).There was large area of resin broken off after 3M light-cured composite resin core fracture.There was only fracture of medental dual-cured resin core and pulpdent dual-cured resin core.Conclusion The bending strength of dual-cured resin is better than that of highly filled light curing composite resin in large tooth hard tissue defect restoration with fiber post-core,and core broken off is rare.Dual-cured resin is better post-core materials.
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PURPOSE: This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS: Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS: Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION: The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.
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Friction , Joints , Titanium , Torque , TungstenABSTRACT
As técnicas existentes para posicionamento do implante zigomático geram variações no contato final osso/implante. Entretanto, clinicamente, não se sabe como isto afeta os valores de sobrevivência. O objetivo deste estudo foi verificar se diferentes modelos biomecânicos afetam os valores de dobramento em implantes zigomáticos não osseointegrados. Assim, duas investigações independentes foram realizadas; 60 implantes zigomáticos de 55 mm de comprimento foram utilizados. Na primeira etapa (M; n = 30), os implantes foram fixados em uma interface metálica. Na segunda etapa (B; n = 30), os implantes foram fixados em osso bovino congelado em temperatura controlada e retirados pouco antes do ensaio. Em cada etapa, as porções apicais dos implantes foram inseridas 8 mm, 10 mm e 12 mm nos blocos de fixação. Os implantes foram montados em 45 graus e submetidos à carga axial até deformação. Os valores máximos de dobramento foram registrados em quilogramas-força e o deslocamento em milímetros. Dentro de cada fase, os dados foram comparados pela análise de variância. O teste t Student foi usado para comparações entre as fases (nas respectivas profundidades de inserção). O nível de significância foi 5%. Na primeira etapa, as diferenças foram significativas apenas entre os grupos M8 e M12 (Anova um critério; p = 0,013). Entretanto, na segunda etapa, a comparação da força máxima entre os grupos não resultou em diferenças estatisticamente significantes. Os valores médios de dobramento nos grupos M foram estatisticamente maiores do que nos grupos B (p < 0,05). Pôde-se concluir que: a) nos modelos M, a resposta mecânica é melhor para implantes com 10 mm de inserção ou mais; b) o modelo biomecânico escolhido altera os valores de resistência ao dobramento.
Current techniques for zygoma dental implant placement can generate different bone-to-implant contact configurations. However, their influence on clinical survival rates is unknown. The aim of this study was to verify the influence of different biomechanical models on bending values for non-osseointegrated zygomatic fixtures. For this, two independent investigations were performed. Sixty 55 mm implants were used. In the first phase (M) (n=30), all implants were secured with a metallic interface. In the second phase (B) (n=30), implants were installed into fresh-frozen bone under controlled temperature conditions just before final test. Three insertion implant depths (8 mm, 10 mm, and 12 mm) were chosen. After, the implants were mounted in a 45-degree inclination and submitted to axial loading at the coronal portion until deformation. Maximum bending strength values were registered in kilograms-force and displacement in millimeters. The analysis of variance test was used to compare data among groups (within each phase). Also, a Student´s t test was performed to compare data between M and B depths. The level of significance was 5%. Significant differences were observed between M8 and M12 (one-way Anova; p = 0,013). However, no significant differences were among B groups. Bending values found in M were statistically higher than in B (p < 0,05). It can be concluded that: 1) In the M phase, the mechanical response is better for 10mm insertion depths or higher, and 2) the biomechanical model influences on the final strength values
Subject(s)
Dental Implants , Materials Testing , Biomechanical PhenomenaABSTRACT
Objectives: To investigate the effect of the thermal treatment on the bending strength of ceramic bars (VM7) treated by the cementation protocol. Material and Methods: Forty ceramic bars (20 x 4 x 1.2 mm) were constructed and randomly distributed into 2 groups (n=20): NT - without treatment/control and T with treatment (50°C above the glass transition temperature, for 15 min). All specimens underwent the cementation process in which one surface of the ceramic bar was etched (20 s) with 10% hydrofluoridric acid, followed by air-water jet washing (60 s), drying (30 s), silane agent application and resin cementation. After storage (distilled water/seven days at 37 ºC), the specimens were submitted to 3-point flexure test at 100% humidity/37 ºC (v=1 mm/min, load cell of 10 kgf). Results: The bending strength values and standard deviations (MPa) were: NT: 19.98 (3.17)a; T: 20.45 (4.67)a (one-way ANOVA and Tukey test, σ=0.05). Conclusions: The thermal treatment did not influence on the bending strength mean values of the ceramics studied.
Objetivos: Investigar o efeito do tratamento térmico, na resistência à flexão, de barras cerâmicas (VM7) tratadas pelo protocolo de cimentação. Material e Métodos: Foram confeccionadas 40 barras cerâmicas (20 x 4 x 1.2 mm) e distribuídas randomicamente em 2 grupos (n=20): NT - sem tratamento/controle e T - com tratamento (50°C acima da temperatura de transição de fases, durante 15 min). Todos os espécimes receberam o processo de cimentação onde uma face da barra cerâmica foi condicionada (20 s) com ácido fluorídrico 10%, seguida pela lavagem jato ar-água (60 s), secagem (30 s), aplicação do silano e cimentação resinosa. Após armazenagem (água destilada/sete dias à 37 ºC), as amostras foram submetidas ao ensaio de flexão 3 pontos em 100% umidade à 37 ºC (v=1 mm/min, célula de carga de 10 kgf). Resultados: Os valores de resistência à flexão e os desvios-padrão (MPa) para os grupos foram: NT: 19.98 (3.17)a; T: 20.45 (4.67)a (ANOVA one-way e Teste de Tukey, σ=0.05). Conclusões: Verificou-se que o fator tratamento térmico não influenciou nos valores médios de resistência à flexão da cerâmica estudada.
Subject(s)
Resin Cements , Thermic TreatmentABSTRACT
STATEMENT OF PROBLEM: The performance and maintenance of implant-supported prostheses are primarily dependent upon load transmission both at the bone-to-implant interface and within the implant-abutment-prosthesis complex. The design of the interface between components has been shown to have a profound influence on the stability of screw joints. PURPOSE. The Purpose of this study was to compare the strength and the fatigue resistance of 1-piece and 2-piece abutment connected to oral implant, utilizing an internal conical interface. MATERIAL AND METHODS: Twenty Implatium(R) tapered implants were embedded to the top of the fixture in acrylic resin blocks. Ten Combi(R)(1-piece) and Dual(R)(2-piece) abutments of the same dimension were assembled to the implants, respectively. The assembled units were mounted in a testing machine. A load was applied perpendicular to the long axis of the assemblies and the loading points was at the distance of 7mm from the block surface. Half of 1-piece and 2-piece abutment-implant units were tested for the evaluation of the bending strength, and the others were cyclically loaded for the evaluation of the fatigue resistance until plastic deformation occurred. Nonparametric statistical analysis was performed for the results. RESULTS: Mean plastic and maximum bending moment were 1,900+/-18Nmm, 3,609+/-106Nmm for the 1-piece abutment, and 1,250+/-31Nmm, 2,688+/-166Nmm for the 2-piece abutment, respectively. Mean cycles and standard deviation when implant-abutment joint showed a first plastic deformation were 238,610+/-44,891. cycles for the 1-piece abutment and 9,476+/-3,541 cycles for the 2-piece abutment. A 1-piece abutment showed significantly higher value than a 2-piece abutment in the first plastic bending moment (P<.05), maximum bending moment (P<.05) and fatigue strength (P<.05). CONCLUSION: Both 1-piece and 2-piece conical abutment had high strength and fatigue resistance and this suggests long-term durability without mechanical complication. However, the 1-piece conical abutment was more stable than the 2-piece conical abutment in the strength and the fatique resistance.
Subject(s)
Axis, Cervical Vertebra , Fatigue , Joints , Plastics , Prostheses and ImplantsABSTRACT
STATEMENT OF PROBLEM: Many kinds of post and core systems are in the market, but there are no clear selection criteria for them. PURPOSE: The purpose of this study was to compare the flexural strength and modulus of elasticity of core materials, and measure the bending strength of post systems made of a variety of materials. MATERIAL AND METHODS: The flexural strength and elastic modulus of thirteen kinds core buildup materials were measured on beams of specimens of 2.0 x 2.0 x 24 +/- 0.1mm. Ten specimens per group were fabricated and loaded on an Instron testing machine at a crosshead speed of 0.25mm/min. A test span of 20 mm was used. The failure loads were recorded and flexural strength calculated with the measured dimensions. The elastic modulus was calculated from the slopes of the linear portions of the stress-strain graphs. Also nine kinds commercially available prefabricated posts made of various materials with similar nominal diameters, approximately 1.25mm, were loaded in a three-point bend test until plastic deformation or failure occurred. Ten posts per group were tested and the obtained data were anaylzed with analysis of variance and compared with the Tukey multiple comparison tests. RESULTS: Clearfil Photo Core and Luxacore had flexural strengths approaching amalgam, but its modulus of elasticity was only about 15% of that of amalgam. The strengths of the glass ionomer and resin modified glass ionomer were very low. The heat pressed glass ceramic core had a high elastic modulus but a relatively low flexural strength approximating that of the lower strength composite resin core materials. The stainless steel, zirconia and carbon fiber post exhibited high bending strengths. The glass fiber posts displayed strengths that were approximately half of the higher strength posts. CONCLUSION: When moderate amounts of coronal tooth structure are to be replaced by a post and core on an anterior tooth, a prefabricated post and high strength, high elastic modulus core may be suitable.
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Carbon , Ceramics , Elastic Modulus , Glass , Hot Temperature , Patient Selection , Plastics , Stainless Steel , ToothABSTRACT
This investigation determined the content of water,organic components and mineral of 80 skullparital bones from cadavers. Basing on semistatic test of anti-bending and anti-compressive mechanicsthe bone mineral contents were measured by quantitative computed tomogrophy. The relationship be-tween bone mineral contents and the mechanical properties was showed. The results suggested thatthere are positive interrelationship between anti-bending strength and skull spongiosa and betweenanti. compressive strength and skull compacta interna (r = O. 51 and O. 34, P