Changes In Microhardness Research Articles

Changes in the properties of bulk-fill resins under conditions of gastroesophageal reflux and bulimia

Aim: Evaluate the roughness, microhardness and color change of different Bulk Fill resins when submitted to the condition of gastroesophageal reflux and bulimia. Methods: 60 specimens (n = 10) of Bulk-Fill composite resins were made: M1 – Filtek™; M2 – Tetric N-Ceram and M3 – OPUS, through a matrix 2x6 mm and light cured by the VALO light source. After polishing, initial analyzes (48 hours - T0) of surface roughness (Ra), microhardness (VHN) and color change (ΔE) were performed. To simulate the oral condition of severe gastroesophageal reflux and bulimia, the specimens were immersed in hydrochloric acid (S1) (pH 1.7) 4 minutes a day, for 7 days. Control group specimens were immersed in artificial saliva (S2). Subsequently to immersions, mechanical brushing was performed for 3 minutes, three times a day, simulating 7 days of brushing. And again, the analyzes of Ra, VHN and ΔE were performed (7 days - T1). Thus, hydrochloric acid immersion, mechanical brushing and Ra analysis were repeated at 14 days (T2) and 21 days (T3); and T2, T3 and T4 (3 years) for VHN and ΔE. Results: After Shapiro-Wilk statistical test, ANOVA and Tukey test with Bonferroni adjustment (p>0.05), M3 showed the lowest Ra at all times compared to the other resins, while the highest Ra was at T0. M1 and T1 showed higher VHN. And M2 and T4 showed higher ΔE. Conclusion: Bulk Fill resins can be indicated for patients with Gastroesophageal Reflux and Bulimia, nonetheless, Tetric N-Ceram resin showed the worst results.

In Vitro Evaluation of the Effects of Different Beverages on the Surface Microhardness of a Single-Shade Universal Composite.

The aim of this in vitro study was to analyze the influence of various beverages on the surface microhardness of a single-shade composite resin. Seventy-five Omnichroma composite discs were fabricated and divided into five subgroups according to the beverages. The groups were Group A: tea; Group B: coffee; Group C: beer; Group D: whisky; and Group E: artificial saliva. The samples were immersed in their respective beverages for 15 minutes per day for 15 days. The Vickers microhardness values were taken before and after the immersion of the composite disc samples in their respective beverages. A one-way analysis of variance (ANOVA) test was conducted using IBM SPSS Statistics software version 23 (IBM Corp., Armonk, New York, USA), with a statistical significance level of 5%. It was observed that there was a reduction in the surface microhardness of the composite resin after immersion in most of the solutions. An increase in the mean percentage change of surface microhardness was observed in the beer group (29%; mean difference = 16.52±12.05), followed by the coffee group (27.2%; mean difference = 15.51±9.28). The least mean percentage change in microhardness was noted in group E, artificial saliva (8.5%; mean difference = 4.81±3.04). The surface microhardness of composite resin can be influenced by the type of beverages used for immersion and the duration of immersion.However, it is important to note that the interaction between composite resin and various beverages is influenced by a complex interplay of multiple variables.

Comparative Evaluation on the Effects of Three Pediatric Syrups on Microhardness, Roughness and Staining of the Primary Teeth Enamel: An In-Vitro Study.

​​​​​Introduction One of the most prevalent oral diseases is dental caries. Syrups are commonly used by children who have difficulty swallowing tablets and capsules. Some medications can make dental caries worse and cause the enamel to erode. Most of the time, parents are unaware that a number of foods, drinks, and syrup-formulated pediatric drugs include sugar, whichcan cause erosion of primary teeth, resulting in plaque accumulation and dental caries.Henceforth, theaim of this study is to assess the effects of pediatric syrups on the microhardness, roughness, and staining ability of primary tooth enamel as a result of daily intake of syrup. Methods Eighty primary teeth, including both anterior and posterior, that required extraction due to pre-shedding mobility were randomly divided into four groups of twenty samples each. Samples were exposed to multivitamin syrup (Rudimin), iron syrup (C Pink), and diuretic syrup (Furosemide). The samples were submerged in 10 mL of the respective medication once daily for five minutes for 21 days. On days 0 and 21, enamel surfaces were assessed for changes in microhardness, roughness, and staining. The microhardness was assessed using a Micro Vickers microhardness tester machine; the roughness was assessed using a Mitutoyo surface roughness tester; and the staining ability was assessed using a spectrophotometer, and data processing was done using the analysis of variance (ANOVA) test andTukey's post hoc analysis. Results The changes in enamel surface for microhardness, roughness, and staining were assessed twice, at days 0 and 21. Group 4 (Furoped) showed a significant difference in surface microhardnessand staining ability of enamel surfaces with a statistically significant p-value (<0.05). When roughness was compared, allthree interventions had a significant difference from the control group, whereas there was no statistically significant difference between the intervention groups. Conclusion This study concludes that pediatric syrups can significantly weaken the enamel of primary teeth, resulting in loss of enamel surface microhardness and roughness making them vulnerable to caries. Since frequent consumption of these syrups is correlated with tooth decay, certain precautions like oral hygiene maintenance and rinsingwith water after taking the syrup should be done to prevent dental caries, as consumption of medicinal syrups by children cannot be avoided.

Effect of Ar+ treatment on thermal stability and micromechanical properties of Fe75Mo5Si6B14 amorphous alloy

The amorphous alloy Fe75Mo5Si6B14 has been shown for investigations. It is shown that the interval of thermal stability has expanded by 80–120 K after ion treatment of the amorphous alloy for 5–25 min, respectively. When Fe75Mo5Si6B14 amorphous alloy treated with Ar + for (5–10) minutes, the relative change in microhardness is of 2.5%–4%, that is, it is within the experimental error of 5%. When the alloy treated for 15–25 min, the microhardness decreases by 7%–13%, that is, a plasticization effect is observed. The effects of expansion of the thermal stability interval and plasticization of an amorphous alloy can be explained by the dissolution of frozen centers of crystallization. This fact is confirmed also by SEM studies of the surface morphology of the amorphous alloy.

Influence of nanosized particles on physical and mechanical properties of galvanic zinc coating

The article presents the results of a study of microhardness and wear resistance of electroplated coatings based on zinc, with the inclusion of Al2O3 nanosized particles in the composition. It has been established that when nano-sized powders are introduced into galvanizing electrolytes, there is a change in microhardness and wear resistance. Thus, when adding from 1 to 9 g/l of Al2O3 nanosized materials to the electrolyte, the microhardness of the resulting coating increased by 10–65%. The best results were obtained for the coating modified with nanosized particles with a concentration of 5 g/l - 657 HV units. Wear resistance tests showed that the total wear of specimens coated with nanocomposite galvanized zinc is 1.5–1.7 times less than that of specimens coated without adding nanosized aluminum oxide particles to the electrolyte.

Determining Homogenization Parameters and Predicting 5182-Sc-Zr Alloy Properties by Artificial Neural Networks.

Artificial neural networks (ANNs) were established for the homogenization and recrystallization heat treatment processes of 5182-Sc-Zr alloy. Microhardness and conductivity testing were utilized to determine the precipitation state of Al3(ScxZr1-x) dispersoids during the homogenization treatment, while electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to observe the microstructure evolution of the alloy. Tensile experiments were performed to test the mechanical properties of the alloy after recrystallization annealing. The two-stage homogenization parameters were determined by studying the changes in microhardness and electrical conductivity of 5182-Sc-Zr alloy after homogenization with the assistance of artificial neural networks: the first-stage homogenization at 275 °C for 20 h and the second-stage homogenization at 440 °C for 12 h. The dispersoids had entirely precipitated after homogenization, and the alloy segregation had improved. A high-accuracy prediction model, incorporating multiple influencing factors through artificial neural networks, was successfully established to predict the mechanical properties of the 5182-Sc-Zr alloy after annealing. Based on the atomic plane spacing in HRTEM, it was determined that the Al3(ScxZr1-x) dispersoids and the Al matrix maintained a good coherence relationship after annealing at 400 °C.

Formation of A Hardened Surface Layer Under Complex Laser Action on the Cutting Edge of Parts Made of Structural Carbon Steels

The purpose of the work was to study the effect of laser modification of the cutting edge on changes in the structure and mechanical properties of the surface layer of parts made of hot–rolled structural carbon steels of grades 20, 35, 45 using a fiber laser.Methods. Structural carbon steels of grades 20, 35, 45 were selected as the objects of the study. To study the effect of laser modification on changes in the structure and mechanical properties of machine parts using laser cutting, special samples were made in the form of plates with a thickness of 2 mm (st20 and st45) and 4 mm (st35). After gas laser cutting, laser modification of the Q-switch cutting edge was performed with a fiber pulsed laser.Results. The regularities of changes in the structure of the zone of gas-laser thermal exposure after laser treatment (cutting, modification) are revealed. It has been established that repeated laser treatment (laser modification) of the cutting edge does not lead to a change in the structural components and microhardness in the zone of gas-laser thermal effects obtained after laser cutting. It has been established that the nature of the microhardness change is the same for all the studied steel grades: the highest values are reached near the surface of gas-laser treatment and are, for example, for steel grade 35 470-560 HV, which is 3,2-3,9 times greater than the initial microhardness (145 HV). Thus, a hardened layer with increased wear resistance is formed on the surface of the part after laser treatment. It is shown that the use of laser surface modification as an additional operation in the manufacture of parts by laser cutting makes it possible to improve the quality (roughness) of the surface layer. At the same time, the greatest effect of reducing roughness is given by laser modification in three passes along the X-Y plane.Conclusion. The results obtained can be used in the creation of resource-saving material processing processes.

Effect of silver diamine fluoride/potassium iodide treatment on the prevention of dental erosion in primary teeth: an in vitro study

IntroductionDental erosion has a great effect on oral health, when diagnosed it is irreversible, this sets the importance of different preventive measures being investigated against dental erosion.AimThis in vitro study aims to evaluate the effectiveness of silver diamine fluoride and Potassium iodide (SDF-KI) in comparison to casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) varnish, sodium fluoride (NaF) varnish, silver diamine fluoride (SDF) alone and deionized water as a control group in the prevention of dental erosion in primary teeth and assessing its staining effect.Materials and methodsForty deciduous teeth enamel specimens were randomly allocated into the five study groups. Tested materials were applied. An erosive challenge was done by immersing the specimens in a citric acid-containing soft drink with pH 2.85, for 5 min, 4 times/day, for 5 days. Changes in surface microhardness, mineral loss, and color change were evaluated besides recording of the surface topography and surface roughness for selected specimens.ResultsThe highest decrease in surface microhardness was recorded in the control group (−85.21 ± 10.60%), with a statistically significant difference (p = 0.002). SDF-KI group (−61.49 ± 21.08%) showed no statistically significant difference when compared to CPP-ACPF, NaF, and SDF groups. For calcium and phosphorous loss, control group was statistically significantly higher compared to the treatment groups (p = 0.003) and (p < 0.001) respectively, while there was no statistically significant difference between the tested treatment groups. The highest mean value for color change was recorded in SDF group (26.26 ± 10.31), followed by SDF-KI group (21.22 ± 12.87) with no statistically significant difference between groups.ConclusionsSDF-KI is as effective as CPP-ACPF, NaF varnishes and SDF in the prevention of dental erosion in primary teeth, there was no statistically significant difference regarding its staining potential.

The Influence of Heat and Cryogenic Treatment on Microstructure Evolution and Mechanical Properties of Laser-Welded AZ31B

The pores and coarse lamellar Mg17Al12 that inevitably occur in the weld zone are the major challenge for laser-welded magnesium (Mg) alloys including AZ31B. In order to improve microstructure uniformity and eliminate welding defects, a new process assisted with combination of heat and cryogenic treatment was applied in this study. The results showed that after solution treatment, the number and size of precipitates decreased and the uniformity of the microstructure improved. After cryogenic treatment, the lamellar Mg17Al12 was cracked into particles, and the grain size was refined. After solution + cryogenic treatment, Al8Mn5 substituted the lamellar Mg17Al12. Through studying the changes in microhardness, precipitates, and microstructure under different treatments, it was found that the conversation of Mg17Al12 from lamellar state into particle-like state as well as the appearance of dispersed Al8Mn5 particles played a second-phase strengthening role in improving the mechanical properties of Mg alloy laser-welded joint, and the tensile strength (258.60 MPa) and elongation (10.90%) of the sample were 4.4% and 32.6% higher than those of the as-welded joint.

Study on the microstructure evolution mechanism of copper single phase alloys under deep undercooling conditions

This article mainly used the deep undercooling technology to treat Cu60Ni40, Cu60Ni38Co2, and Cu60Ni35Co5 alloys to obtain different undercoolings. By using high speed cameras, the rapid solidification process was recorded to analyze the relationship between its evolution law and the magnitude of undercooling. When observing its microstructure, it was also found that there was a critical undercooling degree throughout its entire solidification process. The influence of Co element addition on solidification rate, recalescence effect, and critical undercooling of copper based single-phase alloys under undercooling conditions was explored. EBSD analysis was conducted on the refined microstructure of the alloy that achieved the maximum undercooling, and the significance of grain orientation and orientation difference distribution was found. TEM tests were conducted on a Cu60Ni38Co2 alloy with a maximum undercooling of 259 K, and it was found that there are high-density dislocation networks in some areas within them. Finally, the Vickers hardness of the above alloys was measured and recorded using a microhardness tester (HVS-1000Z), and the evolution between microhardness and undercooling, as well as the changes in microhardness under critical undercooling, were analyzed. Based on the analysis of EBSD, TEM, and microhardness data above, it is found that grain refinement at high undercooling is dominated by recrystallization.

Full analysis of the effects of modeler liquids on the properties of direct resin-based composites: a meta-analysis review of in vitro studies.

This study systematically revised the literature to answer the following question: do modeler liquids (MLs) affect the properties of direct resin-based composites (RBCs)? The review followed the PRISMA statement, and the search was conducted in PubMed, Scopus, Web of Science, Embase, and Lilacs databases. Studies were included if they investigated the properties of RBCs prepared using the restorative dental modeling insertion technique (RDMIT). The risk of bias was performed with the RoBDEMAT tool. Statistical analyses were conducted using Review Manager, and heterogeneity was assessed with the Cochran Q test and I2 statistics. From 309 studies identified, 25 met the eligibility criteria, and 23 were meta-analyzed. In total, 27 MLs and 23 RBCs were evaluated. Modeled and non-modeled RBCs showed similar results in terms of cohesive strength, flexural strength, load-to-fracture, modulus of elasticity, work of fracture, degree of conversion, solubility, weight change, microhardness, and color change. Sorption and roughness benefited from the use of MLs, whereas translucency and whitening index were more adequate in the non-modeled RBCs. Aging affected similarly the modeled and non-modeled RBCs. Most studies showed a moderate risk of bias. Modeled and non-modeled RBCs performed similarly in most of the properties, and the use of non-solvated lubricants offered beneficial effects in some cases. When a balance has to be made between the RDMIT and the conventional technique, our review supports the safe application of modeler liquids for the handling of composite increments during the sculpting fabrication of direct resin-based restorations.

The Effect of Exposure to Dried Fruits on the Surface Micro-Hardness of Dental Enamel

Background: This study investigated the effect of exposure of enamel surfaces to dried fruit suspension including dates, raisins, and dried apricot on their micro-hardness changes.&#x0D; Methods: In this in vitro study, fifty enamel sections of bovine incisor teeth were mounted inside the acrylic resin so that the enamel surface would not be exposed to the acrylic. After surface polishing, the initial micro-hardness was measured by a Vickers hardness-testing machine. The samples were randomly placed into five different solutions including apricot, raisin and date suspension, citric acid (positive control) or sorbitol (negative control), 5 times a day, each time for 5 minutes, and then in artificial saliva for 60 minutes. This process was repeated for 20 days. Eventually, the final micro-hardness of the samples was measured. Micro-hardness changes between groups were compared through ANOVA and TUKEY test using SPSS 23 software with a significance level of P&lt;0.05.&#x0D; Results: After exposure, the micro-hardness of the teeth was significantly reduced in all three suspensions prepared from dried fruit (P&lt;0.05). Apricot and date had the highest and lowest effects on reducing the micro-hardness of teeth, respectively. Sorbitol solution did not have a significant effect on changing the micro-hardness of teeth (P=0.13).&#x0D; Conclusion: The suspension of studied fruits (apricot, raisin, date) causes a significant reduction in micro-hardness of the dental enamel surface, indicating the negative effect of frequent consumption of dried fruits over long periods of time on dental health.

Microstructure and Mechanical Properties of High-Strength, Low-Alloy Steel Thin-Wall Fabricated with Wire and Arc Additive Manufacturing

High-strength, low-alloy (HSLA) steel has attracted much attention in the manufacturing industry because of its good combination of high strength and toughness, low cost, and good formability. Wire and arc additive manufacturing (WAAM) technology can realize the rapid prototyping of HSLA steel parts. This study investigated a 26-layer HSLA steel component fabricated with the WAAM technique. The microstructure of the deposited wall of ER120S-G is mainly acicular ferrite, and there are longitudinal, preferentially growing dendrites along the deposition direction. With the deposition height accumulation, the top sample’s interlayer temperature increases and the amount of acicular ferrite in the microstructure decreases, while the amount of quasi-polygonal ferrite, Widmanstatten ferrite increases. The changes in microhardness were consistent with the corresponding microstructure gradients: the microhardness of the top sample showed a decreasing trend along the deposition direction, while the microhardness of the middle sample was uniform and stable. The present work shows that the mechanical properties of HSLA steel parts deposited using WAAM technology have good strength and toughness. The microstructure gradient of the sample along the deposition direction did not lead to a significant difference in the tensile strength of the sample at different heights. On the contrary, the ductility of the longitudinal sample is slightly lower than that of the transverse sample, indicating some anisotropy in the deposited sample, which is related to the directional growth of grains along the direction of heat flow. From the current work, the thin wall of HSLA steel prepared with the WAAM process has good mechanical properties, which indicates that it is feasible to replace the traditional processing method with the WAAM process to rapidly manufacture an HSLA steel structure meeting the performance requirements.

STUDY OF WEAR OF THE BUILDING-UP ZONE OF MARTENSITE-AUSTENITIC AND SECONDARY HARDENING STEELS OF THE Cr-Mn-Ti SYSTEM

The work deals with wear of the building-up zone of martensite-austenitic and secondary hardening steels of the Cr-Mn-Ti system (partially alloyed with Mo, B, and V). Additional alloying of the studied steels with titanium in the amount of 2…5% supported avoiding cleavages along the building-up zone. It was determined that there is a 7…15 µm wide parent metal zone next to the weld line. The influence of temperature on the weld toughness of the building-up zone was assessed according to the criterion of Malkin and Tetelman. The microhardness of the surface layers of built-up layers and the range of its dispersion are close to the results of laboratory tests, where ТСт ~ 823 K. This approves the formation of structure of metal of contact volumes with the collective effect of heating, plastic deformation and diffusion. It was experimentally approved that the change of microhardness in the sub-surface layers at the wear stage is justified simultaneously with the processes of mutual diffusion of friction pair materials, selective oxidation and thermodiffusion redistribution of the hardening phase under the influence of temperatures and deformations. The diffusion coefficient in the deformed sub-surface layer, which is up to some dozen micrometers thick, is one of the values providing the kinetics of growing of nuclear cracks and development of destruction cracks. The received results provide an opportunity to use martensite-austenitic and secondary hardening steels of the Cr-Mn-Ti system with built-up surface for the hot forming tools.

Effect of grinding conditions of gears made of 20MnCr5 steel after single-piece flow heat treatment on the condition of the surface layer of the tooth working surface

The paper investigated the effect of selected processing conditions during gear grinding on the value and distribution of microhardness and residual stress formed in the technological surface layer of gears after thermochemical treatment (TCT) conducted by a continuous single-piece flow method.The gears were carburised with LPC at 920C, then quenched in a 4D Quenching chamber at 7 bar and tempered at 190C for 3 hours. In the next step, the working surfaces of the gear teeth were ground by supplying grinding fluid (GF) to the grinding zone using the WET method and the MQL method with a minimum amount. Measurements were made on the distribution of microhardness and residual stress formed in the technological surface layer of gears after thermochemical treatment and after the grinding process.The results of the study showed the influence of workpiece speed vw and the method of delivery to the grinding zone GF on selected parameters describing the condition of the technological surface layer of the teeth of gears made of 20MnCr5 steel. The grinding process with a white aluminium oxide grinding wheel causes deterioration in the material's residual stress state. For each of the three analysed workpiece speeds vw, smaller changes in microhardness with respect to the microhardness of the material before grinding occur in the surface layer of samples ground with GF fed with the MQL method. Similarly, residual stress values are in the area of favourable compressive stresses.Environmental considerations and the need to comply with increasingly stringent environmental protection and worker safety regulations are pushing researchers and entrepreneurs to completely eliminate or reduce the consumption of grinding fluids in the grinding process. Based on the research and analysis carried out in this study, it was concluded that applying minimum GF by the MQL method could be an alternative to the conventional WET method.In sustainable manufacturing, it is extremely important to produce high-quality items while reducing the cost of manufacturing and taking care of the environment and workers' health. This includes the manufacture of gears, a basic component used in gear transmissions in the automotive industry, for example. The research has established that it is possible to use the MQL method, which reduces the amount of GF used when grinding the working surfaces of gear teeth, as an alternative to the conventional WET method.The conducted research was the first to determine the most favourable conditions, in terms of the obtained residual stresses and microhardness, for grinding the working surface of gear teeth using the MQL method.

INFLUENCE OF THE MAGNETIC FIELD WITH AN INDUCTION OF 0.4 TL ON THE PLASTIC PROPERTIES OF C2 LEAD

The paper studies the dynamics of deformation characteristics of technically pure C2 lead under the influence of a constant magnetic field with magnetic induction of 0.4 T. Mechanical creep tests were performed, the microhardness of lead samples was measured in the initial state (without the influence of a magnetic field) and under the influence of external magnetic field. Based on the experimental results, creep deformation curves and the dependence of microhardness on the exposure time in a magnetic field are constructed. The stages of creep are determined. A linear stage was identified, at the site of which the creep rate of lead was calculated before and after the application of an external magnetic field. Quantitative changes in the studied characteristics were established. Under the influence of the magnetic field, there was a significant decrease in the creep rate. The relative residual elongation of samples destroyed during creep under the influence of a magnetic field decreased. The initial effect of the influence of a magnetic field with an induction of 0.4 T on the lead microhardness is investigated: the microhardness of the studied samples increases. An increase in the holding time in the magnetic field does not lead to significant changes in the lead microhardness. The maximum magnification is achieved after holding in the magnetic field for 1 hour. The correlation of changes in the creep rate and changes in the microhardness of the material exposed to a magnetic field with magnetic induction of 0.4 T was revealed.

Surface modification of fly ash by waste engine oil under mechanical activation enhanced the sustainable service life of asphalt

Oxidative aging of asphalt leads to changes in its molecular structure and chemical composition, deteriorating the properties. Therefore, extending the service life of asphalt materials is essential for environmental protection and sustainable development. In this study, waste engine oil (WEO) with similar components and chemical composition to asphalt was used to modify the fly ash (FA) surface by a high-energy ball grinding process to produce a well-compatible compound fly ash modifier (CFAM). This process achieved ultra-refinement and surface modification in one step, enhancing the chemical bonding and anchoring force between FA and asphalt, thereby effecting the ageing resistance of the asphalt. Dynamic light scattering tests showed that the oil grinding process enhanced the stability of CFAM, whose median particle size (654 nm) increased by only 103 nm after four months of storage. Thermogravimetric (TG), BET tests showed that the FA surface was grafted with a large amount of WEO, and the CFAM after de-oiling and rinsing had a WEO content of 1.39 wt%, which gave it excellent compatibility with asphalt. The nano-indentation and Fourier transform infrared spectroscopy (FTIR) experiments showed that CFAM reduced the changes in micro hardness, modulus of elasticity, carbonyl content and sulfoxide group content of asphalt before and after ageing and provided an excellent anti-ageing effect. The oil grinding process activated the reactivity of the FA that could chemically bond with the carboxylic acids in the asphalt, stabilizing the chemical components of the asphalt and delaying the ageing of the asphalt, thus achieving sustainable service of the asphalt.

Antimicrobial and cleaning effects of ultrasonic-mediated plasma-loaded microbubbles on Enterococcus faecalis biofilm: an in vitro study

BackgroundEnterococcus faecalis (E. faecalis) is the most frequently isolated bacteria from teeth with root canal treatment failure. This study aims to evaluate the disinfection effect of ultrasonic-mediated cold plasma-loaded microbubbles (PMBs) on 7d E. faecalis biofilm, the mechanical safety and the mechanisms.MethodsThe PMBs were fabricated by a modified emulsification process and the key reactive species, nitric oxide (NO) and hydrogen peroxide (H2O2) were evaluated. The 7d E. faecalis biofilm on human tooth disk was constructed and divided into the following groups: PBS, 2.5%NaOCl, 2%CHX, and different concentrations of PMBs (108 mL−1, 107 mL−1). The disinfection effects and elimination effects were verified with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Microhardness and roughness change of dentin after PMBs treatment were verified respectively.ResultsThe concentration of NO and H2O2 in PMBs increased by 39.99% and 50.97% after ultrasound treatment (p < 0.05) respectively. The CLSM and SEM results indicate that PMBs with ultrasound treatment could remove the bacteria and biofilm components effectively, especially those living in dentin tubules. The 2.5% NaOCl presented an excellent effect against biofilm on dishes, but the elimination effect on dentin tubules is limited. The 2% CHX group exhibits significant disinfection effect. The biosafety tests indicated that there is no significant changes on microhardness and roughness after PMBs with ultrasound treatment (p > 0.05).ConclusionPMBs combined with ultrasound treatment exhibited significant disinfection effect and biofilm removal effect, the mechanical safety is acceptable.

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy.

The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) and HPT state were annealed at 300-550 °C for 0.5, 3, and 12 h. The α-phase formation in Ti-18Zr-15Nb alloy occurs by C-shaped kinetics with a pronounced peak near 400-450 °C for Q state and near 350-450 °C for HPT state, and stops or slows down at higher and lower annealing temperatures. The formation of a nanostructured state in the Ti-18Zr-15Nb alloy as a result of HPT suppresses the β→ω phase transformation during low-temperature annealing (300-350 °C), but activates the β→α phase transformation. In the Q-state the α-phase during annealing at 450-500 °C is formed in the form of plates with a length of tens of microns. The α-phase formed during annealing of nanostructured specimens has the appearance of nanosized particle-grains of predominantly equiaxed shape, distributed between the nanograins of β-phase. The changes in microhardness during annealing of Q-specimens correlate with changes in phase composition during aging.

Effect of silver nanoparticles associated with fluoride on the progression of root dentin caries in vitro.

To assess the anti-proteolytic effect and potential to inhibit dentin root caries progression of a silver nanoparticle and fluoride solution (CNanoF) in comparison to silver diamine fluoride (SDF). 48 specimens of root dentin artificial caries lesion were treated with 38% SDF, CNanoF, CNano or F (n = 6 per group). Ph cycling with demineralization and remineralization solutions simulated caries lesion progression. In addition, specimens were incubated with or without bacterial collagenase in the remineralization solution to induce dentin proteolytic degradation. Dentin degradation was assessed by weight loss rate and hydroxyproline (Hyp) release. Changes in cross-sectional microhardness, and lesion permeability and collagen integrity as determined by confocal laser scanning microscopy indicated potential for further demineralization inhibition. The effect of the solutions on the activity of metalloproteinases (MMP) -2 and -9 was also investigated. Statistical analysis consisted of ANOVA, Kruskal-Wallis, and linear mixed models with post-hoc pairwise Tukey, Dunn, and t-tests (α = 0.05). Treatment with SDF resulted in lower weight loss rate than did other solutions, but all groups showed similar Hyp release (p = 0.183). SDF resulted in greater microhardness at superficial layers of the caries lesions (p<0.05), while there were no differences among CNanoF, CNano, and F. Lesion permeability was similar among all groups after pH cycling (p>0.05), with or without the use of collagenase (p = 0.58). No statistically significant difference was noted among solutions regarding collagen integrity after pH cycling; however, SDF-treated dentin had a significant decrease in collagen integrity when collagenase was used (p = 0.003). Interestingly, only SDF was able to completely inactivate MMP-2 and -9. CNanoF and SDF both potentially prevent dentin degradation during caries lesion progression in vitro; however, SDF was more effective at inhibiting further tissue demineralization.