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@#In recent years, clear aligner technology has been maturing and is rapidly gaining popularity in the orthodontic market for its aesthetic and removable properties. However, despite the background of its large-scale clinical application, mechanical properties of clear aligners need to be studied in depth. This paper reviews the factors influencing mechanical properties of clear aligners and the current status of research to provide evidence-based guidance for clinical application.
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Objective@#To investigate the effects of fiber surface deposited with silicon dioxide films by atomic layer deposition on properties of dental fiber-reinforced composites.@*Methods @#SiO2 films were deposited on the surface of quartz fiber by atomic layer deposition(ALD). Then the quartz fiber was used to manufacture fiber resin composites, which were divided into four groups: A(no soaking agent removal), B(soaking agent removed), C(soaking agent removed and silanization), and D(soaking agent removed, 600 ALD cycles performed and then silanization). Scanning electron microscopy, water contact angle test, hygroscopicity test, CCK8 test and three-point bending test were used to investigate the properties of fiber resin composites.@*Results@#The surface morphology of the quartz fiber treated by ALD was smooth and had no obvious change compared with that before treatment. Moreover, the quartz fiber showed hydrophobicity after silanization. The results of three-point bending test revealed that the mechanical properties of fiber-resin composites modified by ALD were significantly improved(P<0.05). When viewed by scanning electron microscopy, a good interfacial bonding could be seen between quartz fibers and the resin matrix in Group D. In addition, it was found that Group D had low absorbability, low solubility and good biocompatibility. @*Conclusion@#It is shown that deposition of SiO2 films on the quartz fiber by ALD can significantly enhance the mechanical properties of fiber-reinforced composites.
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Znic (Zn) alloys with good cytocompatibility and suitable degradation rate have been a kind of biodegradable metal with great potential for clinical applications. This paper summarizes the biological role of degradable Zn alloy as bone implant materials, discusses the mechanical properties of different Zn alloys and their advantages and disadvantages as bone implant materials, and analyzes the influence of different processing strategies (such as alloying and additive manufacturing) on the mechanical properties of Zn alloys. This paper provides systematic design approaches for biodegradable Zn alloys as bone implant materials in terms of the material selection, product processing, structural topology optimization, and assesses their application prospects with a view to better serve the clinic.
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Orthopedics , Zinc , Alloys , Dental Materials , Prostheses and ImplantsABSTRACT
Objective:To determine the mechanical properties of our self-designed novel cross-locking intramedullary nails and the impact of number of conical locking nails on the fixation through a finite element analysis and specimen experiments.Methods:Mimics 19.0 and SolidWorks 2014 were used to create transverse fracture models of the olecranon which were subjected to fixation with respectively K-wire tension band (KTB) and our self-designed novel cross-locking intramedullary nails (NIN). The strengths of KTB and NIN fixation were analyzed by Ansys. Fifteen human ulna specimens were used to construct a transverse fracture model of the olecranon; an Instron E10000 mechanical testing machine was used to determine mechanical properties in fixation respectively with KTB, one NIN (NIN-1) and 3 NINs (NIN-3).Results:In the finite element analysis, in simulation of the forearm flexed at 45° under a 100 N load, the deformation of the fracture surface of the olecranon in fixation with KTB, NIN-1 and NIN-3 was respectively 0.131 mm, 0.123 mm and 0.121 mm. In the specimen experiments, in simulation of the forearm flexed at 45°, the maximum failure loads for fixation with KTB, NIN-1 and NIN-3 were (313.38±27.68) N, (528.56±53.58) N and (871.04±94.95) N, respectively, showing significant differences among the 3 groups ( P<0.05). The maximum failure load for NIN-3 fixation was significantly greater than that for KTB or NIN-1 fixation, and the maximum failure load for NIN-1 fixation was significantly greater than that for KTB fixation ( P<0.05). Conclusions:Compared with KTB fixation, NIN fixation is more convenient in operation and has better mechanical properties. NIN-3 fixation has the best mechanical properties.
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With extraordinary mechanical properties, articular cartilage is one of the most critical factors in human movement and load transmission. With the increase of sports participation and population aging, more and more patients suffer from cartilage injury and related diseases. Accurate acquisition of mechanical properties for articular cartilage is the key process of cartilage injury and functional evaluation. In this paper, the research progress of indirect estimation for mechanical properties of articular cartilage was summarized. Furthermore, some new perspectives were prospected on mechanical characterization of articular cartilage.
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BACKGROUND: Polyacrylamide hydrogels have good biocompatibility, but their mechanical properties are poor, which affect their application in the field of biomaterials. OBJECTIVE: To prepare the polyacrylamide-acrylic hydrogels with a particular size by micromolding graphical imprinting. METHODS: Polyacrylamide-acrylic hydrogel was prepared by sequentially mixing different volumes of polyacrylamide solution, acrylic acid and ammonium persulfate solution into an orifice plate containing a micromolded patterned seal. Group A: Polyacrylamide solution 1.4 mL, acrylic acid 0.1 mL; group B: Polyacrylamide solution 1.3 mL, acrylic acid 0.2 mL; group C: Polyacrylamide solution 1.2 mL, acrylic acid 0.3 mL; group D: Polyacrylamide solution 1.1 mL, acrylic acid 0.4 mL; group E: Polyacrylamide solution 1.0 mL, acrylic acid 0.5 mL; group F: Polyacrylamide solution 0.9 mL, acrylic acid 0.6 mL. Six groups of ammonium persulfate solution were all 50 µL. The patterned structure of the hydrogel was observed under a light microscope. The mechanical properties of the hydrogel were examined by an electronic universal testing machine. RESULTS AND CONCLUSION: Light microscope showed that the stripes on the surface of each group of hydrogels were clearly visible. The addition of acrylic acid effectively improved the mechanical properties of hydrogels. As the proportion of acrylic acid increased, the mechanical properties of hydrogels gradually increased. These results suggest that polyacrylic acid/acrylamide hydrogel has good mechanical properties and is expected to have good application prospects in the field of tissue engineering damage repair.
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BACKGROUND: Any surface treatments should Improve the bond strength of yttria-stabilized tetragonal zlrconia polycrystal ceramics without damaging the original strength. Currently, there is no Information about the influence of glaze technology on the bond strength of yttria-stabilized tetragonal zlrconia polycrystal ceramics, and its Influence on the material strength Is unclear. OBJECTIVE: To evaluate the effect of glaze technology on the mechanical behavior of yttria-stabilized tetragonal zlrconia polycrystal ceramics and on the bond strength with resin cements. METHODS: Yttria-stabilized tetragonal zlrconia polycrystal ceramics specimens were prepared and randomly divided into four groups: group A: the surface was not treated; group B: sandblasting with 110 urn Al203 particles; group C: glaze + hydrofluoric acid etching; group D: glaze + hydrofluoric acid etching + sllanlzation. The surface morphology, surface roughness, phase transformation, elemental composition, shear bond strength and flexural strength of zlrconia specimens after surface treatments were tested. RESULTS AND CONCLUSION: (1) The surface roughness of treatment groups increased obviously, whose descending order was group C (0.62±0.01) um > group D (0.55±0.02) um > group B (0.11±0.02) um > group A (0.05±0.01) urn (p 0.05). (6) The effect of glaze technology on improving the flexural strength of yttria-stabilized tetragonal zirconia polycrystal ceramics is not as obvious as that of sandblasting, but the bond strength between tetragonal zirconia polycrystal ceramics and resin cements can be significantly Improved with hydrofluoric acid etching and silanization after glaze.
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Tricalcium phosphate (TCP) is one of the most widely used bioceramics for constructing bone tissue engineering scaffold. The three-dimensional (3D) printed TCP scaffold has precise and controllable pore structure, while with the limitation of insufficient mechanical properties. In this study, we investigated the effect of sintering temperature on the mechanical properties of 3D-printed TCP scaffolds in detail, due to the important role of the sintering process on the mechanical properties of bioceramic scaffolds. The morphology, mass and volume shrinkage, porosity, mechanical properties and degradation property of the scaffold was studied. The results showed that the scaffold sintered at 1 150℃ had the maximum volume shrinkage, the minimum porosity and optimal mechanical strength, with the compressive strength of (6.52 ± 0.84) MPa and the compressive modulus of (100.08 ± 18.6) MPa, which could meet the requirements of human cancellous bone. In addition, the 1 150℃ sintered scaffold degraded most slowly in the acidic environment compared to the scaffolds sintered at the other temperatures, demonstrating its optimal mechanical stability over long-term implantation. The scaffold can support bone mesenchymal stem cells (BMSCs) adherence and rapid proliferation and has good biocompatibility. In summary, this paper optimizes the sintering process of 3D printed TCP scaffold and improves its mechanical properties, which lays a foundation for its application as a load-bearing bone.
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Resin composite, which is commonly used as a dental filling material, has some problems, such as poor wear resistance, polymerization shrinkage, and poor dentin marginal adaptability. Preheating of resin composite improves its pro-perties. This paper reviewed the effects of resin composite preheating on its monomer conversion, marginal microleakage, mechanical properties, and irritation on dental pulp.
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Composite Resins , Dental Leakage , Dental Materials , Dental Restoration, Permanent , Materials Testing , Surface PropertiesABSTRACT
Objective To investigate the structure and mechanical properties of pods after dehydration and the biomechanical mechanism of spreading pod seed injection due to torsion crack. Methods The layered pods, the cell size and direction at different cellular layers were analyzed by histology, microstructure observation, mechanical property test and high-speed photography. The process of pod ejection was observed, and the principle of pod ejection was summarized. Results The ejection of pods started from the crack of the bottom, and cracked gradually from the bottom to the top. The cell arrangement of two parts of the same pod was opposite. Each pod was divided into 4 layers wherein the first exterior layer and the middle layer were orthogonal to each other. There was a layer of cells between the first exterior layer and the middle layer, of which the cell wall was broken. In the process of dehydration, fibers in the outer layer shrank and fibers in the middle layer stretched. Conclusions Pod fiber will be contracted in the orthogonal direction after dehydration to accumulate elastic performance and generate pre-stress, and finally the pod is cracked to release the pre-stress.
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Methods: According to blend of different components and proportion of acellular cartilage extracellular matrix of pig, nano-hydroxyapatite, and alginate, the osteochondral integration of multi-layered scaffold was prepared by using freeze-drying and physical and chemical cross-linking technology. The cartilage layer was consisted of acellular cartilage extracellular matrix; the middle layer was consisted of acellular cartilage extracellular matrix and alginate; and the bone layer was consisted of nano-hydroxyapatite, alginate, and acellular cartilage extracellular matrix. The biological and mechanics characteristic of the osteochondral integration of multi-layered scaffold were evaluated by morphology observation, scanning electron microscope observation, Micro-CT observation, porosity and pore size determination, water absorption capacity determination, mechanical testing (compression modulus and layer adhesive strength), biocompatibility testing [L929 cell proliferation on scaffold assessed by MTT assay, and growth of green fluorescent protein (GFP)-labeled Sprague Dawley rats' bone marrow mesenchumal stem cells (BMSCs) on scaffolds].
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Objective To study the mechanical properties of collagen molecules by molecular dynamics simulation,and to determine the relationship between the mechanical properties of the microstructure of cartilage and the macroscopic mechanical properties. Methods Obtaining the collagen molecular model from the protein database and using GROMACS molecular dynamics simulation software,an analog box was built with a size of 24 nm× 3.2 nm × 3.2 nm. The simulation system contained 6 719 water molecules, 20 sodium ions and 20 chloride ions. This solution was equivalent to a saline environment. The uniaxial tensile simulation of collagen molecules was executed under the conditions of different temperature,different tensile rates and different pressures in this environment.Results When the temperature was constant, the tensile rate and the elastic modulus of collagen increased; when the tensile rate was certain, the temperature of the simulation system rose while the modulus of elasticity decreased;under the conditions of certain temperature and tensile rate, the pressure of the system gradually increased,and its modulus of elasticity decreased gradually. Conclusion Through the uniaxial tensile simulation of collagen molecules under different conditions,the mechanical laws of collagen molecules are obtained.There is a certain correlation between the elastic modulus and the tensile strain during the stretching process,and a way of thinking is provided on the study of the correlation of cartilage rate from the microscopic aspect.
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Objective To determine the influence of Fe2O3 coloring method to the mechanical and transparency parameter of dental zirconia.Methods Presintered zirconia blocks were coverd with zirconia powder blended with different ratio of Fe2O3,then sintered to 1450℃.Mechanical property and transparency parameter were calculated.Results The L* value was in the range from 64.91 to 90.94.The a* value was in the range from 1.27 to 12.70.The b* value was in the range from 1.02 to 38.66.There was no significant difference (P ＞ 0.05) of the flexural strength and in each group with the increase of Fe2O3.Conclusion This method produced dental zirconia specimens with light yellow to amber brown colors with the increase of Fe2O3 and no significant influence of mechanical property and transparency.
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Objective To explore the mechanical properties of erythrocytes in the patients with hypertension.Methods Venous blood of 32 patients with hypertension were collected and divided into three groups of H1,H2,and H3 (degree Ⅰ,Ⅱ,Ⅲ),with 8 cases of healthy adults into a control group.Erythrocytes were isolated,the diameter,height and elastic modulus were detected by the atomic force microscope (AFM).Statistical analysis was carried out.Results The RDW-CV of H2,H3 were much larger than the control group (P＜0.05,P＜0.01);The height of erythrocyte in H2,H3 groups were lower than that of the control group (P＜0.05).The elastic modulus of H 1,H2 groups were larger compared with normal erythrocytes (P＜0.05).Furthermore,erythrocytes elastic modulus correlated with RDW-CV (R2=0.629).Conclusion Hypertension could affect the elasticity modulus of erythrocytes.AFM could be an effective tool in measuring the mechanical characteristics of erythrocytes at single cell level.This study investigates the relationship between hypertension and the structure and function of erythrocytes from a biomechanical aspect.
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Poly lactic acid (PLA) fibers a biodegradable fiber produced from PLA resin by melt spinning, solvent spinning or electrostatic spinning. Based on the excellent safety, comfortability, environmental protection and good mechanical properties, PLA can be widely applied in textile fabric, nonwoven, filler fabric and many downstream health products application, such as sanitary napkins, baby diapers, facial masks, and wipes.
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Biotechnology , Chemical Industry , Lactic Acid , Polyesters , Chemistry , PolymersABSTRACT
Objective To develop a small-diameter tissue-engineered blood vessels which possesses normal blood vessels physiological structure, good biocompatibility, and mechanical properties. And it was evaluated by mechanical and biological of national standard of medi-cal transfusion material. Methods The bio-derived material were regarded as the ground substance, and it was evaluated by mechanical and biological of national standard after composite modification. Results The axial and radial tensile stress of the blood vessel was 23. 14 N and 36. 79 N respectively, and it was greater than the standard 7. 5N. The tensile rate of the axial and radial was 95. 19% and 80. 24% respec-tively, which were higher than the standard value 20%. The suture strength of the blood vessel was 13. 71 N, which was conform to the me-chanical requirement. Mainly used blood vessels or its extracts to detect the pH of the blood vessels is in the scope of control deionized water pH (7. 5 ± 1. 5);the hemolysis rate was 1. 3972% which was less than 5%;the whole blood coagulation time was 50% longer than the con-trol level, and there was no stimulation after intradermal injection. Conclusion With bio-derived material as the ground substance and com-positely modified, this kind od blood vessels is conform to the mechanical and biological of national standard, and it has the potential of clini-cal application which could play an important role in the replacement therapy of small-diameter vascular xenografts.
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PURPOSE: The purpose of present study is to compare mechanical properties and microstructural characteristics of fractured surface for cast, 3-D printing laser sintered and CAD/CAM milled cobalt-chromium (Co-Cr) alloy specimens and to investigate whether laser sintered technique is adequate for dental applications. MATERIALS AND METHODS: Thirty six flat disc shape Co-Cr alloy specimens were fabricated for surface hardness test and divided into three groups according to the manufacturing methods; 12 specimens for casting (n=12), 12 specimens for laser sintered technology (n=12) and 12 specimens for milled technology (n=12). Twelve dumbbell shape specimens for each group were also fabricated for a tensile test. Statistical comparisons of the mechanical properties for the alloys were performed by Kruskal-Wallis test followed by Mann-Whitney and Bonferroni test. The microstructural characteristics of fractured surfaces were examined using SEM. RESULTS: There were significant differences in the mean Vickers hardness values between all groups and the cast specimen showed the highest (455.88 Hv) while the CAD/CAM milled specimen showed the lowest (243.40 Hv). Significant differences were found among the three groups for ultimate tensile strength, 0.2% yield stress, elongation, and elastic modulus. The highest ultimate tensile strength value (1442.94 MPa) was shown in the milled group and the highest 0.2% yield strength (1136.15 MPa) was shown in the laser sintered group. CONCLUSION: Different manufacturing methods influence the mechanical properties and microstructure of the fractured surfaces in Co-Cr alloys. The cast Co-Cr alloy specimens showed the highest Vickers hardness, and the CAD/CAM milled specimens revealed the highest tensile strength value. All alloys represent adequate mechanical properties satisfying the ISO standards of dental alloy.
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Alloys , Dental Alloys , Elastic Modulus , Hardness , Hardness Tests , Tensile StrengthABSTRACT
The silk egg case and orb web of spiders are elaborate structures that are assembled from a number of components. We analysed the structure, the amino acid and fibre compositions, and the tensile properties of the silk fibres of the egg case of Nephila clavata. SEM shows that the outer and inner covers of the egg case consist of thick, medium and thin silk fibres. The silk fibres of the outer cover of the egg case are probably produced by the major and minor ampullate glands. The silk fibres of the inner cover of the egg case from cylindrical glands appears to be distinct from the silk fibres of the major ampullate glands based on their micro-morphology, mole percent amino acid composition and types, and tensile behaviour and properties. Collectively, our investigations show that N. clavata uses silk fibres from relatively few glands in varying combinations to achieve different physical and chemical properties (e.g., color, diameter, morphology and amino acid composition) and functional and mechanical properties in the different layers of the egg case.
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Objective To explore mechanical property changes of methyl vinyl silicone rubber modified by ferric nanoparticles and its dispersed phase.Methods Mechanical properties such as Shore A hardness,tensile strength,elongation at break,tearing rate of permanent deformation and tearing strength of pre-prepared ironic nanoparticle enhanced silicone rubber and carbon-coated ferric particle reinforced silicone rubber were tested according to national standards.A thermal field emission scanning electron microscope (TFE-SEM) was used to investigate the morphology of both surface and fracture of the composite materials and to observe the dispersion of ferric nanoparticles in them.Results Mean values of Shore A hardness,tensile strength,elongation at break,tearing permanent deformation rate and tear strength of modified composites increased with the increasing amounts of ferric nanoparticles,however,when the quota of ironic nanoparticles in the composite formula were greater than 17 phr,carbon-coated ferric nanoparticles more than 19 phr,the mean values of tensile strength of two composites stopped increasing and presented the declining trend.When the quota of ferric nanoparticles in the formula exceeding 15 phr,the mean values of elongation at break and tear strength began to decrease in the formula ratio of silicone rubber/ferric nanoparticles up to 85:15,while the Shore A hardness of samples increased all the way.Ferric nanoparticles dispersed evenly on the surface of composites.Nanopowder aggregation in the fracture surface of both composites could be observed at the formula ratio of 85:15 of silicone rubber/iron nanoparticle and 87:13 of silicone rubber/carbon-coated iron specimen.Conclusion Effect of iron nanapareticles and carbon-coated ferric nanoparticles on the mechanical properties of the reinforced methyl vinyl silicone rubber depends on the nanoparticle size,additive amount and agglomeration.
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STATEMENT OF PROBLEM: Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. PURPOSE: The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). MATERIAL AND METHODS: Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad Sackingen, Germany) were prepared in 40 mm (length) x 4 mm (width) x 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and 225degrees C for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences (alpha= .05). RESULTS: The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below 125degrees C for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above 150degrees C, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. CONCLUSION: The monoclinic phase started to appear after aging treatment above 100degrees C. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above 175degrees C. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.