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1.
Food Chem ; 398: 133881, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35964558

RESUMO

The effect of energetic neutral argon (EAr) atoms on the short and long-term retrogradation was studied, and the retrograded starch was used to prepare bioplastic films for better mechanical and barrier properties. Kithul starch showed higher short and long-term retrogradation after treatment. The EAr atoms treatment increased amylose content and amylose leaching; it facilitated the short-term retrogradation. The more pronounced effect of long-term retrogradation in starch after treatment increased the enthalpy of retrogradation (ΔHR), hardness, and syneresis and decreased the light transmittance and freeze-thaw stability. Bioplastic films made from retrograded starch after EAr atoms treatment exhibited significantly (p ≤ 0.05) higher relative crystallinity; it could be attributed to the higher starch retrogradation after cold plasma treatment. The films of retrograded EAr atoms treated starch showed higher mechanical strength and barrier properties. These results revealed that bioplastic films from retrograded EAr atoms treated starch could potentially substitute the single-use petroleum-based packaging films.


Assuntos
Gases em Plasma , Amido , Amilose , Dureza , Termodinâmica
2.
Sci Total Environ ; 858(Pt 1): 159554, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36265637

RESUMO

Site-specific water quality criteria considering hydrochemical conditions are needed for zoning control of environmental risks. However, the differences in water quality parameters between regions have not been fully considered in the current research on water quality criteria and risk assessment of lead. In this study, lead concentration and total hardness (TH) data of surface water in 13 major river basins and 31 administrative regions in China were collected. Based on the normalization of the TH of the toxicity data, the short-term and long-term water quality criteria of lead in China's surface water in the specific TH condition (100 mg/L) were derived using the species sensitivity distribution method, which were 90.7 µg/L and 2.1 µg/L, respectively. Furthermore, this study provided general derivation formulas for the water quality criteria based on the TH of surface water and obtained the site-specific criteria for different regions/basins in China. On this basis, an ecological risk assessment considering the TH was proposed for the first time. The results showed that there was a clear risk of lead in the Pearl River Basin and the rivers in Zhejiang-Fujian. The southern coastal provinces were at an unacceptable risk level, although the lead concentrations in the surface water were medium; the opposite was true in northern China, which meant that a high concentration of lead did not necessarily pose a high ecological risk and about 25 % of the variation in the predicted risk can be explained by the TH in Monte Carlo simulation.


Assuntos
Poluentes Químicos da Água , Qualidade da Água , Chumbo/toxicidade , Dureza , Poluentes Químicos da Água/análise , Rios , Medição de Risco , China , Monitoramento Ambiental
3.
Food Chem ; 404(Pt A): 134514, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36270227

RESUMO

Differences in texture and digestive properties of different parts in 80 °C-boiled abalone muscle (adductor and transition part) after different processing time were investigated. With the extension of boiling time, the shear force and hardness of adductor increased first (6 min) and then decreased (30 min and 240 min), while the two indexes of transition part dramatically decreased after boiling for 6 min and then maintained until 240 min. Meanwhile, for adductor, the degree of protein hydrolysis, protein digestibility, and peptide transport levels declined with the extension of boiling time; While for transition part, those protein digestion and transport indexes significantly decreased first (6 min and 30 min) and then increased (240 min). By contrast, the adductor contained higher myofibrillar proteins content but lower collagen content than the transition part, which contributed to the differences in texture and digestive properties of the boiled samples.


Assuntos
Digestão , Gastrópodes , Animais , Alimentos Marinhos , Músculos , Dureza
4.
Food Res Int ; 162(Pt A): 112020, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36461243

RESUMO

Aiming at consumer acceptability of brown rice such as cooking difficulty and coarse taste, the effects of defatting and hydrothermal treatment alone or in combination on the texture and sensory score of cooked brown rice were studied, and the improvement mechanism was explored through cooking quality and microscopic morphology. The results showed that defatting combined with hydrothermal treatment could significantly improve the quality of brown rice, the hardness and chewiness of treated cooked brown rice decreased respectively from 20.385 N and 10.221 N to 14.494 N and 6.886 N, and the sensory score increased from 68.90 to 83.50. The room temperature water absorption rate of the treated brown rice increased from 10.72 % to 29.71 %, which was much higher than that of polished rice. The cooking quality of the treated brown rice was obviously improved, the optimal cooking time decreased from 30.33 min to 22.67 min, and the heating water absorption, volume expansion rate and solid loss increased from 147.32 %, 255.20 % and 13.35 mg/g to 219.15 %, 400.39 % and 22.49 mg/g, respectively. Scanning electron microscope showed that defatting combined with hydrothermal treatment significantly increased cracks and micropores of brown rice grains, which may be the intrinsic reason for the improvement in room temperature water absorption rate and cooking quality of brown rice and thus eating quality of cooked brown rice. The results are of great significance for promoting the staple consumption of whole-grain brown rice with broad application prospects.


Assuntos
Oryza , Culinária , Grãos Integrais , Água , Dureza
5.
J Oleo Sci ; 71(12): 1735-1741, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36464286

RESUMO

The quality and processing characters of shortening are strongly influenced by the temperature fluctuation during storage and handling. Some chemical components, especially the presence of emulsifiers in shortening formula might be attributed to the quality change of shortening in response to temperature fluctuation. In this work, the effect of emulsifiers on the mechanical properties, crystalline structure, and crystalline transformation of fat was investigated with a palm oil-based shortening under varied storage temperature (4°C, 12 h - 28°C, 12 h, cycle reciprocating). Results show that the shortening without emulsifiers deteriorated easily with a severe separation of liquid oil and reduction of hardness, which was owing to the aggregation of crystals, and the appearance to high proportion of ß crystals at the later stage in storage (day 7 and day 14). However, the addition of the emulsifiers such as sorbitan monopalmitate (SMP), Glyceryl monostearate (GMS), and Glycerol monopalmitate (GMP) ameliorated the production of ß crystals effectively. Among the tested emulsifiers, the shortening adding GMS showed the best quality, which remained stable in multiple cycles up to 14 times. The findings will guide the use of emulsifiers in palm fat processing.


Assuntos
Emulsificantes , Óleo de Palmeira , Temperatura , Dureza
6.
J Oleo Sci ; 71(12): 1725-1733, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36464285

RESUMO

Candelilla wax (CW) is used as an oil-gelling agent in cosmetic sticks. However, its hardness is inadequate compared to those of hydrocarbon waxes such as paraffin. In this study, behenyl behenate (BB), an additive plant-derived wax ester with a high melting point, was shown to improve the oil-gel hardness of CW.Although the gel with BB alone had a relatively low gel hardness, when BB was mixed with CW at a ratio of 70:30 (CW:BB), the gel hardness significantly increased to four times that of the CW gel. The hardness of the CW and BB mixtures was higher than that of paraffin wax, which is used to solidify cosmetic oils. An increase in gel hardness was not observed when additives with chemical structures similar to those of BB, such as stearyl stearate (which has a lower molecular weight than BB) and behenic acid or behenyl alcohol (which are components of BB), were blended.Scanning electron microscopy indicated the presence of many spherical clusters comprising fine crystallites in the CW gel. This morphology was in contrast to that of paraffin wax gel, in which only plate crystals were observed. It was concluded that this heterogeneous structure led to the low gel hardness of CW. When BB was added to CW, the spherical clusters disappeared, and the internal structure changed to a homogeneous card-house structure composed of plate crystals.


Assuntos
Ésteres , Parafina , Ceras , Dureza , Excipientes
7.
Braz. j. oral sci ; 21: e226202, jan.-dez. 2022. ilus
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1393187

RESUMO

Aim: Resin modified glass ionomer (RMGI) is class of material that can be used as sealant for preventing and arresting the progression of caries in pits and fissures. As these are hybrid materials, their properties can be affected by factors related to the polymerization process. Therefore, this study aimed to evaluate the influence of different generations of LED curing units (Elipar DeepCure-L and VALO Grand) on Knoop microhardness values (KHN) of RMGI sealants (Clinpro XT and Vitremer). Methods: Forty cylindrical specimens (6mm ø x 1 mm high) were prepared according to the manufacturer's instructions and divided into four groups (n=10) according to the type of RMGI and LED used. The KHN of the top surface of each sample was calculated 7 days after light-curing. Data were submitted to two-way ANOVA (α = 0.05). Results: Vitremer had higher KHN values than Clinpro XT after using both LEDs (p<0.0001), but especially when light-cured with the use of VALO Grand (p<0.0001). Whereas the KHN value of Clinpro was not influenced by the LED device (p>0.05). Conclusions: Top surface microhardness values of RGMI sealants were affected by both material composition and generations of LED curing units used. Third generation LED curing units seemed to be more efficient for the polymerization of RMGI-based sealants


Assuntos
Selantes de Fossas e Fissuras , Luzes de Cura Dentária , Polimerização , Dureza
8.
Braz. j. oral sci ; 21: e226630, jan.-dez. 2022. ilus
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1393209

RESUMO

Aim: The present study aimed to asses enamel microhardness after office bleaching with diode laser and LED light compared to the conventional bleaching procedure. Methods: Thirty-nine human premolar teeth were collected and randomly divided into three groups regarding of the bleaching technique. Group 1: Snow O bleaching gel with LED light-curing unit; Group 2: Snow L bleaching gel with diode laser irradiation; and Group 3: Opalescence Boost bleaching gel with no light source in group 3. Enamel surface changes were evaluated in one tooth in each study group and one intact tooth as a reference under a scanning electron microscope (SEM). In the remaining samples (n=12), enamel microhardness was determined by Vickers microhardness test before and after bleaching. Data were analyzed with repeated-measures ANOVA to compare microhardness changes, followed by post hoc Tukey tests at the 0.05 significance level. Results: Enamel microhardness decreased in all the groups after bleaching, with the maximum decrease in microhardness in the Snow O bleaching group with LED light, which was significantly higher than the other groups (P=0.002). The two other groups did not exhibit any significant difference in microhardness decrease (P>0.05). Conclusion:Based on the limitations of this study, it can be concluded power bleaching with 980nm diode laser was less time-consuming compare to conventional bleaching procedure and yielded better outcomes in terms of enamel surface microhardness compared to the use of an LED light-curing unit


Assuntos
Clareamento Dental/efeitos adversos , Esmalte Dentário , Lasers Semicondutores , Luzes de Cura Dentária , Dureza
9.
Dent Mater ; 38(12): e308-e317, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36435637

RESUMO

OBJECTIVES: To evaluate the fracture toughness and brittleness of a newly developed CAD/CAM resin composite block and compare it with five other resin composite blocks and one polymer-infiltrated ceramic block. METHODS: Fracture toughness was determined through single-edge notched beam (SENB) method according to ASTM D5045-14. Parallelepiped specimens (thickness × width × length = 1.8 × 3.6 × âˆ¼18 mm) with a V notch (length = âˆ¼1.8 mm) (n = 10) were made from block materials using a low-speed water-cooled diamond precision saw and razor blade. Brittleness index (BI) was calculated from Vickers hardness and fracture toughness. Data were analyzed using one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). RESULTS: The experimental block showed significantly higher fracture toughness than all commercial block materials (p < 0.001) and has a brittleness index similar to most commercial blocks (p > 0.05) which have significantly lower brittleness index than Vita Enamic (p < 0.001). A moderate or strong correlation was observed between fracture toughness and flexural strength (Pearson's correlation coefficient R = 0.66) or diametral tensile strength (R = 0.86) or filler loading (R = 0.66), and between brittleness and Vickers hardness (R = 0.87). SIGNIFICANCE: The new composite block exhibited significantly higher fracture toughness and lower brittleness among the commercial CAD/CAM composite block materials tested, indicating a lower tendency to fracture and marginal chipping, and better machinability. The new composite block with higher fracture toughness and lower brittleness is suitable to use in the fabrication of CAD/CAM indirect restorations with potential long-term clinical success.


Assuntos
Resinas Compostas , Desenho Assistido por Computador , Resistência à Flexão , Dureza , Resistência à Tração
10.
Dent Mater ; 38(12): 2030-2040, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36424203

RESUMO

OBJECTIVES: The objectives of this study were to evaluate the mechanical properties of lithium disilicate components produced by additive manufacturing (AM) and to assess the effect of build orientation on the resistance to fracture. METHODS: Oversized bars were printed with a glass-filled photoactive resin using a digital light processing technique. After sintering and post-processing, flexure and chevron notch fracture toughness bars were obtained in three principal orientations (0°, 45°, and 90°) with respect to the build direction. Mechanical properties were obtained according to the relevant ASTM standards. The hardness, indentation fracture resistance, and elastic modulus were measured for each orientation, and a Weibull analysis was conducted with the flexure responses. Fractography of the fracture surfaces was performed to identify the failure origins. RESULTS: The 0° orientation exhibited characteristic strength, Weibull modulus, and elastic modulus of 313 MPa, 4.42, and 168 ± 3 GPa, respectively, which are comparable to lithium disilicate materials from traditional processes. However, build orientation contributed significantly to the flexure strength, elastic modulus, and Weibull modulus; the characteristic strengths for the 45° and 90° build orientations were 86 MPa and 177 MPa, respectively. The primary contribution to the orientation dependence was the number of residual build layer-related flaws from incomplete union between printed layers. Of note, hardness and the fracture toughness were not dependent on build orientation. SIGNIFICANCE: AM of lithium disilicate materials can achieve the mechanical properties of materials produced by traditionally processing. Thus, while further process development is warranted, the outlook for dentistry is promising.


Assuntos
Porcelana Dentária , Resistência à Flexão , Polimerização , Dureza
11.
BMC Oral Health ; 22(1): 489, 2022 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-36376830

RESUMO

BACKGROUND: To evaluate the efficacy of fluoride-containing toothpastes with different technologies to remineralize artificial caries lesions in enamel. METHODS: Bovine enamel blocks were divided into three thirds: intact (untreated), demineralized (artificial caries lesion), and treated (caries lesion, pH cycling with dentifrices). Enamel blocks were randomly distributed into five groups (n = 12): Fluoride-free toothpaste, Colgate Oral Care (NC); Arginine-containing toothpaste, Colgate Total Daily Repair (PC); Silicate-based fluoride toothpaste: REFIX technology, regenerador + sensitive (RDC), NR-5 technology, Regenerate Enamel Science (RES), and NOVAMIN technology, Sensodyne Repair and Protect (SRP). The specimens were submitted to a pH cycling model for 6 days. The efficacy of the toothpastes was estimated by calculating the surface microhardness recovery (%SMHR) and the fluorescence recovery (ΔFRE) with quantitative light-induced fluorescence. The cross-sectional micromorphology of the enamel surface was also assessed using scanning electron microscopy. Elemental analyses (weight%) were determined with an energy-dispersive X-ray spectrometer (EDS). The results were compared to that of the control (NC). Data were statistically analyzed (5%). RESULTS: %SMHR could be ranked as follows: RDC = PC = RES = SRP > NC. Significantly higher %SMHR and ΔFRE means were observed after enamel treatment with RDC (22.7 and 46.9, respectively). PC (%SMHR = 18.8) was as efficacious as RDC to recover the surface microhardness with a significantly lower mean of ΔFRE (19.5). Only RDC was able to promote the formation of a mineralized layer on the surface of enamel enriched with silicon on the surface. CONCLUSIONS: The silicate-based fluoride toothpaste containing REFIX technology demonstrated greater efficacy in the remineralizing artificial caries than the other products.


Assuntos
Cárie Dentária , Cremes Dentais , Animais , Bovinos , Humanos , Cariostáticos/uso terapêutico , Estudos Transversais , Cárie Dentária/prevenção & controle , Cárie Dentária/patologia , Esmalte Dentário/patologia , Fluoretos/uso terapêutico , Dureza , Concentração de Íons de Hidrogênio , Fluoreto de Sódio , Tecnologia , Remineralização Dentária/métodos , Cremes Dentais/uso terapêutico
12.
Naturwissenschaften ; 109(6): 52, 2022 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-36322292

RESUMO

The radula, a chitinous membrane spiked with teeth, is the molluscan autapomorphy for the gathering and processing of food. The teeth, as actual interfaces between the organism and the ingesta, act as load transmitting regions and have to withstand high stresses during foraging - without structural failure or high degrees of wear. Mechanisms contributing to this were studied previously in paludomid gastropods from Lake Tanganyika. For some species, gradients in hardness and Young's modulus along the teeth were detected, enabling the bending and relying of teeth onto the next row, distributing the stresses more equally. The here presented study on one of them - Lavigeria grandis - aims at shedding light on the origin of these functional gradients. The mechanical properties were identified by nanoindentation technique and compared to the elemental composition, determined by elemental dispersive X-ray spectroscopy (EDX, EDS). This was done for the complete radular (mature and immature tooth rows), resulting in overall 236 EDX and 700 nanoindentation measurements. Even though teeth showed regional differences in elemental composition, we could not correlate the mechanical gradients with the elemental proportions. By applying confocal laser scanning microscopy (CLSM), we were finally able to relate the mechanical properties with the degree of tanning. CLSM is a common technique used on arthropod cuticle, but was never applied on radular teeth before. In general, we found that nanoindentation and CLSM techniques complement one another, as for example, CLSM is capable of revealing heterogeneities in material or micro-gradients, which leads to a better understanding of the functionalities of biological materials and structures.


Assuntos
Gastrópodes , Dente , Animais , Dureza , Módulo de Elasticidade
13.
Hist Sci ; 60(4): 500-523, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36427244

RESUMO

Historians of natural history have shown that the study of plants, animals, and minerals was a form of connoisseurship in the eighteenth century. Historians of early modern experiments have linked scientific knowledge to the manual skills of artisans. I combine these two insights, arguing that connoisseurship in the sciences meant learning to touch, not just learning to look. The focus is on gems and mineralogy in eighteenth-century France. I show, firstly, that the study of gems was linked to the connoisseurship ("connoissance") of paintings. Next, books on gems were closely related to the new mineralogical treatises that emerged in the middle of the eighteenth century. These treatises formalized a distinction between "Oriental" and "Occidental" gems that was also a distinction between hard and soft gems. The best judges of hardness were gem cutters, a group that participated in mineralogy through the culture of collecting. Finally, the knowledge of cutters contributed to the quantification of hardness in the form of the hardness scale and the scratch sclerometer.


Assuntos
Conhecimento , História Natural , Dureza , História Natural/história , França , Minerais
14.
Int J Occup Saf Ergon ; 28(4): 2668-2675, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36337028

RESUMO

This work aimed to study the end of service life of soles of protective footwear resistant to selected mechanical factors and mineral oil. Three sole variants were examined; made from poly(ethylene-co-vinyl acetate) (EVA), poly(vinyl chloride) (PVC) and polyurethane (PU), currently widely used in all-rubber protective footwear. The preliminary study focused on the abrasion resistance and bending strength of the three sole materials after different times of exposure to mineral oil. Changes in density and hardness of the examined materials were evaluated following exposure to cyclical factors. Statistical analysis was performed to identify significant differences between the three types of polymers in terms of abrasion resistance, density and hardness following exposure to mineral oil for three different periods. Surface morphology of the sole materials was examined by means of scanning electron microscopy. The presented studies elucidate the effects of mineral oil on the basic mechanical parameters of all-rubber footwear soles.


Assuntos
Óleo Mineral , Sapatos , Humanos , Borracha , Poliuretanos , Dureza
15.
Dent Mater ; 38(12): 1866-1877, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36202659

RESUMO

OBJECTIVES: To investigate the depth of cure (DoC), fracture toughness (KIC) and wear of ion releasing resin-based composite (RBC) restorative materials. METHODS: Two ion releasing RBCs, Activa (ACT) and Cention-N (CN) were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). The DoC was measured in a 10-mm deep semi-circular metal mold with a 2-mm internal radius (n = 8). The molds were irradiated from one end for 20-s. The Knoop hardness (KH) was measured at 0.5-mm intervals from the surface after the specimens had been stored at 37 °C for 24-h. To measure the KIC, single-edge-notched specimens (n = 15/group) were prepared (25×5x2.5-mm) for a 3-point bending test and then stored for either 1 or 30-days in water at 37 °C. Disk-shaped specimens (n = 10) were subjected to 250,000-load cycles of 49-N using a chewing simulator against spherical steatite antagonists. DoC and wear data were analyzed by one-way ANOVA and Tukey post hoc tests (p ≤ 0.05). KIC data were analyzed by two-way ANOVA and one-way ANOVA, and the Tukey post hoc test (p ≤ 0.05). In addition, an independent t-test was used to determine if storage time had any effect (α = 0.05) on the KIC of each material. RESULTS: Maximum hardness value was the highest for Z350 and the lowest for ACT. The depth at which 80% of the maximum KH, was the highest for CN (9.2 mm) and the lowest for Z350 (2 mm). All tested materials met the manufacturers' claims for DoC. After 1-day, the highest KIC values were recorded for ACT and the lowest for Fuji-II-LC. Water storage (30-days) significantly reduced the KIC value for all materials except Fuji-II-LC. The highest wear rate values were recorded for CN followed by ACT. SIGNIFICANCE: All tested materials met their manufacturers' claims for DoC. Water storage for 30-days significantly reduced the fracture toughness for ACT and CN. Wear was significantly higher for ACT and CN.


Assuntos
Resinas Compostas , Cimentos de Ionômeros de Vidro , Teste de Materiais , Materiais Dentários , Dureza , Água , Propriedades de Superfície
16.
Dent Mater J ; 41(6): 916-922, 2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36288940

RESUMO

The aim of this in vitro study was to evaluate the wear and surface hardness of nine materials for conventional manufacturing, subtractive milling, and 3D printing of occlusal splints, as well as to evaluate the differences in wear and surface hardness between rigid and flexible 3D-printed occlusal splint materials. Two-body wear and Vickers hardness tests were performed. The vertical wear depth and Vickers hardness values were statistically analyzed. Vertical wear depth and surface hardness values were statistically significant among the investigated materials (p<0.05). The lowest vertical wear depth was observed for the heat-cured resin (27.5±2.4 µm), PMMA-based milled material (30.5±2.8 µm), and autopolymerizing resin (36.7±6.3 µm), with no statistical difference (p<0.05). Flexible 3D-printed and CAD-CAM milled polycarbonate-based splint materials displayed lower surface hardness and higher wear than the PMMA-based materials. PMMA-based splint materials displayed the most consistent surface hardness and wear resistance regardless of the manufacturing technology.


Assuntos
Placas Oclusais , Polimetil Metacrilato , Dureza , Teste de Materiais , Desenho Assistido por Computador , Impressão Tridimensional , Propriedades de Superfície
17.
J Biomech ; 144: 111350, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36288678

RESUMO

Characterizing the mechanical properties of different anatomical quadrants of bones has been conducted in the literature to help understand the correlations among bone morphometric, densitometric, and material properties. However, although there are data to compare four quadrants of the long bones of the adult, there is very limited research on the young adult especially young female. Hence, nine tibia mid-shaft specimens were harvested from nine 8-week-old C57BL/6J female mice, which roughly correspond to the age range of juvenile to young adult, with one left tibia being harvested from one animal. A total of 144 indentation tests were performed with four indentations per quadrant and each of nine tibia specimens being divided into four quadrants. The Oliver and Pharr methods were used to calculate the indentation modulus and hardness. One-way ANOVA and the Kruskal-Wallis nonparametric test were used to study the influence of different anatomical quadrants on the indentation modulus and hardness. The results showed that the indentation modulus of the 8-week-old mouse tibia shaft was 18.94 ± 0.91 GPa, and the hardness was 0.51 ± 0.02 GPa. The influence of circumferential anatomical quadrants on the tibial shaft indentation modulus (p = 0.398) and hardness (p = 0.895) was not statistically significant. These methods and results could potentially help study treatments for young female long bones by comprehensively understanding the effect of treatments on four quadrants, considering collagen fiber, the degree of mineralization, and the changes of collagen cross-linking through high-resolution nanoindentation.


Assuntos
Diáfises , Tíbia , Camundongos , Feminino , Animais , Camundongos Endogâmicos C57BL , Dureza , Colágeno
18.
J Pak Med Assoc ; 72(8): 1479-1482, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36280905

RESUMO

Objectives: To evaluate the depth of cure in smart dentin replacement bulkfill composite resins polymerized by constant, pulse and ramped light-emitting diode curing modes. METHODS: The in vitro experimental study was conducted in November and December 2019 at the dental clinics of Aga Khan University Hospital, Karachi, and comprised of cylindrical composite specimens 8x4mm in size which were polymerised in Teflon moulds using light-emitting diode under constant mode in Group 1, pulse mode in Group 2 and ramped mode in Group 3. Once polymerised, each specimen was extruded from the mould and, using the International Organisation for Standardisation-4049 scrapping method, uncured resin was removed. Specimen lengths were measured with a Vernier calliper. Each specimen was measured thrice and the mean was taken as the depth of cure. Data was analysed using SPSS 24. RESULTS: Of the 33 specimens, there were 11(33.3%) in each of the 3 groups. Mean depth of cure in Group 1 was 2.92±0.29mm, in Group 2 it was 2.88±0.27mm, and it was 3.18±0.26mm in Group 3. The difference between Group 2 and Group 3 was statistically significant (p<0.05). Conclusion: Maximum depth of cure of smart dentin replacement bulkfill composite was achieved by ramped cure mode of light-emitting diode unit, followed by constant and pulse modes.


Assuntos
Resinas Compostas , Politetrafluoretileno , Humanos , Teste de Materiais , Polimerização , Dureza
19.
J Prosthet Dent ; 128(4): 822.e1-822.e9, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36202632

RESUMO

STATEMENT OF PROBLEM: Studies on the microhardness of novel additively manufactured polymers compared with well-established low- and high-viscosity composite resins with regard to chemical composition are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of hydrothermal aging on the microhardness of various conventional and additively manufactured polymers. MATERIAL AND METHODS: Cylindrically shaped specimens (N=240, n=10 per group) (Ø10×2 mm) were either additively manufactured (6 groups) or conventionally (6 groups) manufactured by using 3D (Optiprint Temp [OP; Dentona]; C&B MFH [ND; NextDent]; Saremco print CROWNTEC [SA; Saremco Dental AG]; Temp Print [TP; GC]; 3DELTA ETEMP [DM; Deltamed]; MED690 [ST; Stratasys, Ltd]) or conventional low (Gradia Direct [GR; GC]; Clearfil Majesty [CM; Kuraray Noritake]; Tetric EvoCeram [TE; Ivoclar AG]) and high (Gradia Direct Flo [GR-F; GC]; Clearfil Majesty Flow [CM-F; Kuraray Noritake]; Tetric EvoFlow [TE-F; Ivoclar AG]) viscous materials. All specimens were randomly allotted to 2 different aging methods (no-aging [dry] or aging by thermocycling [TC], ×6000, 5 °C-55 °C) and Vickers hardness (VH) tested (ZHV30; Zwick). Three indentations were made on each specimen (0.98-N load, duration 15 seconds). The calculated average microhardness value of each specimen was statistically analyzed by using 2-way ANOVA and Tukey post hoc tests (α=.05). Two-parameter Weibull distribution was calculated to predict the reliability of material type and aging method on VH. RESULTS: The mean ±standard deviation VH ranged between 17 ±0.5 VHN and 68 ±0.5 VHN in the following ascending order: group STa.05). The mean ±standard deviation of HV for aged (37 ±1 VHN) and nonaged (35 ±1 VHN) specimens were statistically similar (P>.05). The Weibull distribution values presented the highest shape for the aged group SA (37.81). CONCLUSIONS: The choice of the material had a significant effect and resulted in lower hardness for the 3-dimensionally printed materials than for the conventional composite resins. Under fatigue conditions, the choice of the material showed no significant difference when the Vickers microhardness was evaluated.


Assuntos
Resinas Compostas , Polímeros , Polímeros/química , Viscosidade , Reprodutibilidade dos Testes , Teste de Materiais , Resinas Compostas/química , Dureza , Propriedades de Superfície
20.
Niger J Clin Pract ; 25(10): 1751-1757, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36308250

RESUMO

Background: Polymerization plays an important role in the optical and mechanical properties resin composite materials. Aim: The current study aimed to evaluate the effect of different polymerization times on the color change, translucency parameter (TP), and surface hardness of resin composites after thermocycling. Materials and Methods: Microhybrid resin composite (Filtek Z250; used in the control group) and bulk-fill resin composites (Filtek One Bulk-Fill Restorative, Tetric EvoCeram Bulk-Fill, and Tetric N-Ceram Bulk-Fill) were used. Each bulk-fill composite was placed as a single layer. Polymerization of the bulk-fill composites in the first group was completed in 20 s, and that in the second group was completed in 40 s (n = 10). Filtek Z250's polymerization was completed with 2 mm (20 s) + 2 mm (20 s). The color change (ΔE00) and translucency parameter (TP00) were calculated using the CIEDE2000 formula. Before and after thermocycling, the TP and surface hardness values were measured. The data were analyzed using one- and two-way analysis of variance, paired-samples t-test, and Tukey's test (P < 0.05). Results: After thermocycling, the ΔE00 values of the resin composite samples were 1.66-2.56. Compared to the control group, the Filtek One Bulk-Fill 20 s group exhibited the lowest color change values. The Filtek Z250 group exhibited lower TP and significantly higher microhardness values than the other bulk-fill resin groups before and after thermocycling (P < 0.05). There were no observed differences in the Tetric N-Ceram and Tetric EvoCeram groups before and after thermocycling. Conclusion: Under the conditions of 10,000 thermal cycles, different curing times did not affect the color change and hardness values of the bulk-fill materials. However, differences were observed among the composite materials. After thermocycling, the surface hardness and TP values decreased in all the resin composites. Depending on the material content, effective results can be obtained from the 20 s polymerization of bulk-fill resin composites.


Assuntos
Resinas Compostas , Materiais Dentários , Humanos , Dureza , Polimerização , Teste de Materiais , Propriedades de Superfície
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