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Statement of problem A vinegar-hydrogen peroxide mixture has been reported to be effective in eliminating Candida albicans and Staphylococcus aureus from acrylic resin, and its action has been reported to be comparable with that of sodium hypochlorite or peracetic acid. However, the effects of this mixture on cobalt-chromium alloys remain unknown. Purpose The purpose of this in vitro study was to evaluate the surface roughness, Knoop microhardness, surface free energy, and wettability of a cobalt-chromium alloy when exposed to a vinegar-hydrogen peroxide mixture. Material and methods Fifty specimens of cobalt-chromium alloy were fabricated and immersed for 900 minutes, simulating 3 months of a daily 10-minute immersion in the following chemical agents (n=10): distilled water (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water dilution in 1:1 ratio (HP); white-wine vinegar and water dilution in 1:1 ratio (V); and vinegar and hydrogen peroxide mixture in 1:1 ratio (VHP). Surface roughness, Knoop microhardness, surface free energy, and wettability were measured with single blinding before and after immersions. Data were statistically analyzed by using 2-way repeated measures ANOVA (α=.05). Results The vinegar-hydrogen peroxide mixture did not affect the surface roughness or Knoop microhardness. However, 0.5% sodium hypochlorite significantly increased the roughness and decreased microhardness. Surface free energy and wettability increased after immersions, regardless of the types of solution. Conclusions Immersion in a vinegar-hydrogen peroxide mixture did not affect the surface characteristics of a cobalt-chromium alloy.

Differences in dentin microstructure have been used as a tool for dietary reconstruction; however, the extent that diet is associated with this aspect of dental morphology has yet to be empirically tested. We conducted microhardness tests of mammalian dentin sections, hypothesizing that species with adaptations to particularly hard diets would have softer dentin, owing to a higher proportion of soft intertubular dentin. Species adapted to abrasive diets, in contrast, should have harder dentin, resulting from a higher proportion of hypermineralized peritubular dentin. We examined molar dentin hardness in ten mammalian taxa with durophagous diets, abrasive diets, and a comparative "control" group of mechanical generalists. Samples included six primate taxa and four non-primate species representing various dietary regimes. Our results reveal significant variation among taxa in overall hardness, but the data do not distinguish between hard and abrasive diets. Several taxa with generalized (i.e., mechanically diverse) diets resemble each other in exhibiting large variance in hardness measurements and comparably soft dentin. The high variation in these species appears to be either a functional signal supporting the niche variation hypothesis or indicate the absence of sustained unidirectional selective pressure. A possible phylogenetic signal of dentin hardness in the data also holds promise for future systematic investigations.

Objective To investigate the effect of light-curing distance on the effectiveness of cure (EC) of bulk-fill resin-based composites (RBCs). Materials and methods Two bulk-fill RBCs (a Tetric N-Ceram Bulk Fill (TN) and a Filtek Bulk Fill (FK)) are evaluated. Specimens (4 mm high) are cured for 20 s at different distances (0 mm (D0), 2 mm (D2), 4 mm (D4), 6 mm (D6) and 8 mm (D8)) and stored for 24 h in 100% relative humidity at 37 °C. The top and bottom surface hardness (SH) (n = 12) are assessed using a Knoop microhardness tester and the EC is calculated. The EC is characterized by the hardness ratio (HR) (mean bottom: top SH). An HR of 0.8 is used as the benchmark for an effective/adequate cure. Data are analyzed using one-way analysis of variance and Tukey’s post hoc test (α = 0.05). Correlations between the top and bottom surfaces are examined using the Pearson correlation (α = 0.05). Results For the TN, the HR at D8 is significantly lower than all other light-curing distances, while for the FK, it is significantly lower than D0 only. Conclusion The effect of light-curing distance on the EC of bulk-fill RBCs is material dependent. Notwithstanding the light-curing distance, the EC of the FK and TN is below the threshold HR value of 0.8 when photopolymerized for 20 s in 4 mm increments in black opaque molds.

Statement of problem The acrylic resin used in dental prostheses, which is subject to changes in its properties caused by hygiene chemicals, brushing, and colored beverages, can benefit from mechanical polishing methods. However, studies evaluating whether such procedures can be performed continuously without damaging the prosthetic materials are lacking. Purpose The purpose of this in vitro study was to evaluate the effect of a continuous mechanical polishing protocol on the color stainability, surface roughness, microhardness, and mass of a denture base acrylic resin. Material and methods The polishing protocol was tested in specimens submitted to one of the following conditions: immersion in coffee (CF) (n=20); toothbrushing (Br, 35 600 cycles in a brushing simulation machine) (n=20); and immersion in 1% sodium hypochlorite (HYP) (n=20). For each condition, half of the specimens were polished (aluminum oxide paste and felt wheel attached to an electric motor, 3000 rpm) at simulated biweekly intervals. Two groups (n=10) of specimens were immersed in distilled water and used as the control for the immersion groups. Thus, the present study consisted of a total of 8 groups (n=80). Before and after simulated periods of 12 and 24 months, surface roughness was evaluated by using a contact profilometer; a spectrophotometer was used to calculate color changes (ΔE00); and a Knoop microdurometer and a precision balance were used to assess microhardness and mass changes. Data were compared by using 2-way mixed ANOVA. The Tukey HSD and Student t tests were used for post hoc analysis (α=.05). Results The polishing influenced surface roughness (Br, CF, HYP: P 1.30) for the Br group, exceeding the clinical acceptability threshold for the CF group (ΔE00= 2.51). Polishing reduced ΔE00 in these groups, making values similar to those found in the groups immersed in distilled water. The color in the HYP group was not influenced by polishing. Conclusions In general, the tested polishing protocol reduced the deleterious effects of brushing and contact with 1% sodium hypochlorite and coffee, reducing surface roughness and color change without affecting microhardness and mass in any clinically relevant way.

Objectives To evaluate the biaxial flexural strength (BFS), flexural modulus (BFM), and Knoop microhardness (KHN) of incremental and bulk-filled resin-based composites (RBCs) using extended curing exposure times. Materials and methods Disc specimens (n = 8; 6-mm diameter) were fabricated using three stacked molds (0.5-mm thick for the top and bottom molds, and a 1-mm-thick center mold for the conventional and 3-mm thick for the bulk-fill RBCs). Conventional (Tetric EvoCeram/TCE and Filtek Z250/FIZ) and bulk-fill RBCs (Tetric EvoCeram Bulk Fill/TBF and Filtek One Bulk Fill Restorative/FOB) were evaluated. The stacked RBC-filled molds were light-cured for (1) the manufacturer-recommended exposure (MRE) duration; (2) 50%, and (3) 100% extension of the MRE. The BFS, BFM, and KHN of the top and bottom discs were measured. BFS and BFM were analyzed by three-way ANOVA (material*curing time*depth) and Tukey's post hoc (α = 0.05). KHN was analyzed by two-way ANOVA (curing time*depth) and Tukey's post hoc (α = 0.05). Results Extending the exposure duration did not change the BFS and BFM on the top of the RBCs, but the BFS and KHN increased at the bottom of bulk-fill RBCs. For the conventional RBCs, TCE showed the highest increase on BFS at the bottom, going from 53.6 MPa at T1 to 69.9 at T3. Among the bulk-fill RBCs, FOB presented the highest increase on the bottom BFS (T1: 101.0 ± 19.9 MPa, T3: 147.6 ± 12.9 MPa). For all RBCs and exposure times, BFS and KHN were lower at the bottom. Only FIZ and FOB reached a bottom-to-top hardness ratio of 80%, at T3 and T2. Conclusion A significant increase on the BFS and KHN on the bottom of bulk-fill RBCs can be observed when the time of exposure to the curing light is double the MRE. However, extended exposure does not eliminate differences on the BFS and KHN between the shallow and deep regions of RBCs. TCE and TBF failed to reach an acceptable B/T hardness ratio at all evaluated exposure times. Clinical relevance Mechanical properties of RBCs can be affected by insufficient polymerization, specially at deeper regions of the increment. Therefore, clinicians should consider applying twice the MRE to curing-light to polymerize the maximal increment thickness of bulk-fill RBCs.

The anisotropy of the properties of a ceramic cutting insert (for three faces) obtained by the lithography-based technology from the Al2O3 + ZrO2 composite has been studied. The study was carried out using the indentation method and Mayer’s law. This method, in contrast to the bending test, excludes the sample destruction. All the studies were carried out on three faces of a ceramic cutting insert made of a composite Al2O3 + ZrO2. The behavior of the Mayer index was studied in the range of loads from 2 to 20 kg and from 0.2 to 1 kg. The results of studying the density, phase composition and microstructure of each face of the sample are presented. The study of the adhesion of the printed layers were also carried out using a Knoop indenter. No anisotropy of the hardness was observed in the load range up to 10 kg. It is shown that a layered structure present in the sample, contributes to the hardness anisotropy under the load of 20 kg and more. No anisotropy of the fracture toughness is observed in the load range of 2 – 20 kg. The results of using a Knoop indenter revealed a high adhesion between 3D printed layers. Studies using a Knoop indenter have indicated high adhesion between the layers of 3D printing.

Background: There are still controversies in the literature as to which is the best resinous cementing agent. Due to this fact and the immense availability of types and brands of cementing agents, further studies are needed to evaluate the properties of these important dental materials. Objective: To assess the degree of monomer conversion (DC) and Knoop microhardness (KHN) of four resin cements: two conventional dual-cured resin cements (EnForce and RelyXARC); one self-etching cement (RelyXU100); and one chemically-activated cement (Cement-Post). Methods: 20 Pieces were made to assess KHN, and 20 to assess DC (n = 5). The DC was analyzed using a Fourier-transform infrared spectrometer, and KHN of the base and the top of the pieces were assessed using the Future-Tech microhardness tester. The data of KHN were statistically analyzed by two-factor ANOVA, and data related to DC were analyzed by the Kruskal-Wallis non-parametric test. The analysis of the correlation between KHN and DC of the cementing agents was performed by linear regression. Results: Dual-cured cements exhibited lower average KHN values at the base than at the top of the pieces (p 0.05). The chemically-activated cement exhibited the lowest averages of KHN and DC values (p 2 = 0.96); however, a specific hardness value could not be correlated to a specific DC value. Conclusion: Preferably, dual-cured resin cements (conventional or self-etching) should be used. Chemically-activated resin cements should be avoided due to their lower averages of DC and KHN values.

Based on the density functional theory (DFT), a systematic theoretical investigation on the structural parameters and finite temperature thermo-physical properties of cubic silicon carbide (3C-SiC) is reported. Our results regarding the structural parameters, melting point, Knoop micro hardness, and thermal conductivity show generally satisfactory accord with experiment and other calculated findings of the present literature. The material of interest is predicted to transform from the zinc-blende (B3) phase to the rock-salt phase (B1) at a pressure of around 70 GPa, which corresponds to a volume collapse of around 18.1%. This agrees well with several experimental and previous theoretical data. Based on the Debye model, the thermo-physical properties at temperatures up to 2000 K and for pressures up to 70 GPa are analyzed and discussed. The authors’ results show a monotonous change of the thermo-physical properties of the material in question against temperature or pressure. This accords well with the general trend commonly reported in the present literature.

Objective This study investigated the handling and surface characteristics of universal resin composites and determined the interrelations among the composites’ handling, mechanical, and physical properties. Methods Five recently introduced universal resin composites were tested. Twelve specimens per material were used to measure the stiffness and stickiness (handling properties) of the resin composite pastes. Additionally, surface properties (Knoop hardness number [KHN], surface roughness [Sa], surface gloss [SG], water contact angle [CA], and surface free energy [SFE]) of cured resin composites were determined in 12 specimens per material immediately after preparation (baseline) and after subjection to thermal cycles (TCs). Results Handling and surface properties of the resin composites were material dependent. All the resin composites showed significantly lower KHN in the post-TC subgroups than that in the baseline subgroups. However, the influence of TC on the other surface properties was dependent on the material used. Some resin composites did not indicate any significant differences in Sa, SG, or CA between the baseline and post-TC groups. Significance Although the resin composites in the baseline groups presented with different handling and surface properties, the surface properties of most of the composites were significantly affected by TC. Extremely strong positive or negative correlations were observed between stiffness and stickiness, KHN and Sa, KHN and SG, Sa and SG, and CA and SFE. Most correlations between the handling and surface properties were weak. Therefore, the selection of resin composites in clinical situations should be based on comprehensive consideration of their properties.

Background Oral care products containing bioactive agents obtained from extracts of plant drugs were launched. This in vitro study investigated the effects of herbal-containing toothpastes associated or not with fluoride to remineralize the enamel after cariogenic challenge with pH cycling. The chemical and physical factors of toothpastes and the enamel surface roughness after brushing were also analyzed. Material and methods Sixty bovine enamel blocks were obtained and divided into 3 thirds: intact (untreated), demineralized (artificial caries lesion), and treated (caries lesion, pH cycling, and brushing with toothpastes). Toothpastes containing herbal compounds contained no fluoride [Galla chinensis (GCH)], low-F concentration [D'Or (DOR); Herbal Bliss (HBL)], or a different fluoride type [Elmex Anticaries (EAC)]. The results were compared to NaF-containing toothpastes: 1450 and 5000 ppm. Enamel blocks were brushed with the toothpastes using a pH-cycling model (7 days). The Knoop hardness (25g/10s) of the surface and the longitudinal sections were then evaluated. The percentage of surface hardness recovery (%SHR) was calculated. The enamel surface roughness, pH, particle size, zeta potential, and polydispersity index of toothpaste slurries were also evaluated. Data were statistically analyzed (α=5%). Results No significance was observed when %SHR was compared (p>0.05). DOR, GCH, and HBL were more effective in remineralizing the enamel subsurface. Significantly higher surface roughness was observed when treated with EAC and GCH (p Conclusions All toothpastes were able to remineralize the enamel, especially the subsurface, with results equal or better than that of standard toothpastes. Key words:Enamel, hardness, roughness, toothpaste, tooth remineralization.

The purpose of this study was to evaluate the influence of the chemical polishing, when compared to the mechanical polish, in the sorption, solubility and microhardness of a heat-polymerizable acrylic resin. The heatactivated acrylic resin used was Clássico (Art. Odontológicos Clássico Ltda., S.P.). The properties of sorption and the solubility were tested in accordance with International Organization for Standartization (ISO) specification n. 1567, making 20 samples in the format of disks, divided aleatory in two groups, where the first group received lhe mechanical polish with abrasive pastes, and the second, the chemical polish during IOS, in the chemical polisher PQ 9000 (série 4868-2, Termotron do Brasil Ltda., Piracicaba, SP). The samples were maintained in a desiccator with silica gel, at 37 DC, until the moment they reached constant mass (M1), obtained in a scale with resolution of 0,0001g. The samples were submerged in distilled water, at 37 Uc, for 7 days, when it was Obtained new mass value (M2). The difference between M1 and M2 divided by the volume Of each sample resulted in the sorption. The samples were desiccated again until they reach constant mass (M3). The difference between M1 and M3 divided by the volume of each sample resulted in the solubility Of the same ones. For the Knoop microhardness measurement, were made 20 specimens of acrylic resin, of which 10 samples received the mechanical polish and the others, the chemical polish. The Knoop microhardness test was made with a NU Research Microscope (VEB Carl Zeiss JENAGermany). The results indicated that the technique of the chemical polish is acceptable when considered the sorption property, even so unviable with the solubility property, in accordance with the specification n.1567 of ISO. The chemical polish also reduced significantly the superficial microhardness of the acrylic resin, which consequences can interfere in the clinical performance of the material.

This study investigates the flexural properties, Knoop hardness number (KHN), and wear behavior of computer-aided design and computer-aided manufacturing (CAD/CAM) resin blocks and compares these values with those of conventional resin composites for direct restoration (RCDs). Four CAD/CAM resin blocks and two RCDs are compared. Ten specimens per material are used to obtain the flexural properties according to ISO 6872 specifications, and five specimens per material are used for KHN measurement. For sliding impact wear testing, twelve specimens are prepared. Confocal laser scanning microscopy (LSM) is used to determine maximum facet depth and volume loss. Polished material surfaces and worn surfaces after wear testing are observed using scanning electron microscopy and LSM. While measured flexural properties and KHN are found to be material-dependent, CAD/CAM resin blocks exhibit higher wear resistance than RCDs. CAD/CAM resin blocks polymerized at high-pressure and high-temperature are found to exhibit wear behaviors far superior to those of RCDs.

This in-vitro study was done to compare the effect of LED light curing system on polymerization and hardness of two composite resins system. A Total of 40 samples, 20 samples prepared using silorane based – Filtek LS and 20 samples prepared using methacrylate based- Filtek Z350 XT in a plastic molds with diameter of 8 mm and thickness of 3 mm and cured with LED curing light. knoop hardness testing was done using a 50grams load and a dwell time of 15sec and percentage depth of cure is calculated and statistical analysis was performed using Student t- test. Results showed that silorane based composite was found to have better hardness n depth of cure than methacrylate based composite. Top surface have better hardness than bottom surface.

AISI 1045 steel is a steel of medium carbon, widely used in machinery, the automotive industry, and the food industry, among others. Therefore, to fulfill its purpose, it is necessary to improve its mechanical resistance, wear resistance and resistance to fatigue through different surface heat treatments. Variables such as heating time and hence speed affect the thickness of the hardened layer and the microstructural characteristics of the area affected by heat treatment. The inspection of the transformation of phases during the treatment and the thickness of the boundary layer is generated by determining the hardness of the material, whose procedure is subject to the ASTM E92-17 and E384-17standards, which establish the methodology to be followed. Therefore, the objective of this work is to quantify the effect of three heating times at 1123 K on the hardening of AISI 1045 steel and the regularity of the hardened layer to ensure its functionality as a component subjected to friction, in addition to developing a table of equivalences between the Knoop (HK), Vickers (HK) and Rockwell C (HRC) hardness scales.

The tribological behavior of Ni-based WC-Co coatings is analyzed. The coatings were deposited on gray cast iron substrates in a spray and fuse process using SuperJet Eutalloy deposition equipment, varying the oxygen flow conditions in the flame. The crystallographic structure of the coatings was characterized via the X-ray diffraction (XRD) technique. The microhardness was measured on the surface and in cross sections of the coatings by means of a Knoop microhardness tester. The topography and the morphological characteristics of the coatings and the tribo-surfaces were examined using scanning electron microscopy (SEM) and confocal microscopy, while the chemical composition was measured by means of energy-dispersive X-ray spectroscopy (EDS). The tribological behavior of the coatings was examined via a cohesion-adhesion scratch test, using cross sections of the coatings. Furthermore, two wear tests were carried out, using the pin-on-disk method under ASTM G99 standard and an ASTM standard G65 sand/rubber wheel abrasion wear test. The wear of the coatings showed a close relationship to the porosity in the metal matrix; since then, in the abrasive wear test, a high porosity is related with lower hardness in the coatings; likewise, a low hardness is related with a high wear.

Statement of problem How the polymerization shrinkage, loading, and mechanical properties of luting materials affect the shrinkage and functional stresses in ceramic laminate veneers (CLVs) with and without tooth preparation is unclear. Purpose The purpose of this finite element analysis (FEA) study was to evaluate the effect of the polymerization shrinkage, functional loading, and mechanical properties of different luting materials on the stresses in ultrathin 0.3-mm CLVs with and without tooth preparation. Material and methods Three resin cements, RelyX Veneer (RV), Allcem Veneer APS (AV), Variolink Esthetic LC (VE), and 1 flowable composite resin, Tetric N-Flow (TF), were tested for post-gel shrinkage (Shr), Knoop hardness (KHN), elastic modulus (E), compressive strength (CS), and diametral tensile strength (DTS). IPS e.max CAD disks of 0.3-mm thickness were made for simulating the effects of light attenuation. Eight 2-dimensional finite element models (Marc-Mentat) of a maxillary central incisor were generated to evaluate the polymerization shrinkage stress of different materials for luting 0.3-mm CLVs with or without tooth preparation and the stress during functional loading by using a modified von Mises criterion (mvm). Collected data from Shr, KHN, and E were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). Results Light attenuation by the 0.3-mm ceramic disk did not significantly affect the E values, but Shr was significantly lower in VE (26%) and TF (35%). TF had lower volumetric Shr (%) when interposing a ceramic disk (0.31%). Both tested tooth preparation options showed similar stress distributions from polymerization shrinkage or functional loading, with higher stress concentration on the incisal edge and also on the cervical surface. The model featuring tooth preparation and RV resin cement had the highest and VE the lowest stress levels. Conclusions The flowable composite resin had similar mechanical properties as the resin cements. The stress distribution from shrinkage and functional loading was similar for both techniques with or without tooth preparation.

OBJECTIVE This study investigated the dentin remineralization effect of the application of a functionalized tri-calcium phosphate (fTCP) dentifrice and a silver diamine fluoride (SDF) solution. MATERIAL AND METHODS The materials used were: a fluoride-containing dentifrice with fTCP (fTCP＋), a fluoride-containing dentifrice without fTCP (fTCP-) and a 38% SDF solution. Following treatment, the dentin slabs were immersed in a 0.1-M lactic acid buffer solution and then placed in artificial saliva. This procedure was repeated three times daily for 28 days. The propagation time of longitudinal ultrasonic velocities (UV) and the Knoop hardness (KH) of the samples were measured. The samples were also observed using scanning electron microscopy. RESULTS The SDF and fTCP＋ groups showed higher UV than the fTCP - group regardless of the application method. The F-SDF group at 28 days showed significantly higher UV (4121 ± 102 m/s) than the F-fTCP + group (3731 ± 65 m/s) (p

Objectives This study aimed to evaluate the effect of in-office bleaching on the enamel surface and the efficacy of calcium silicate-sodium phosphate-fluoride salt (CS) and NovaMin bioactive glass (NM) dentifrice in remineralizing bleached enamel. Materials and Methods Forty extracted premolars were sectioned mesio-distally, and the facial and lingual enamel were flattened and polished. The samples were equally divided into nonbleached and bleached with 38% hydrogen peroxide (HP). Each group was further divided according to the remineralization protocol (n = 10); no remineralization treatment (nontreated), CS, or NM, applied for 3 minutes two times/day for 7 days, or CS combined with NR-5 boosting serum (CS+NR-5) applied for 3 minutes once/day for 3 days. The average Knoop hardness number (KHN) and surface roughness (utilizing atomic force microscopy) were measured. Surface topography/elemental analysis was analyzed by using scanning electron microscopy/energy dispersive X-ray analysis. All the tests were performed at baseline, after bleaching, and following each remineralization protocol. Data were statistically analyzed by two-way analysis of variance and Bonferroni post hoc multiple comparison tests (α = 0.05). Results HP significantly reduced KHN and increased roughness (p < 0.05). All remineralization materials increased the hardness and reduced the surface roughness after bleaching except NM, which demonstrated significantly increased roughness (p < 0.05). Ca/P ratio decreased after bleaching (p < 0.05), and following treatment, CS and CS+NR-5 exhibited higher remineralization capacity in comparison to NM (p < 0.05). Conclusion Although none of the material tested was able to reverse the negative effect of high-concentration in-office HP on enamel completely, the remineralization efficacy of CS and CS+NR-5 was superior to that of NM.

Objective Formulate experimental adhesives containing titanium dioxide nanotubes (nt-TiO2) or titanium dioxide nanotubes with a triazine-methacrylate monomer (nt-TiO2:TAT) and evaluate the effect of these fillers on the physical, chemical, and biological properties of the adhesives. Methods First, nt-TiO2 were synthesized via a hydrothermal method. The nt-TiO2 were mixed with a triazine-methacrylate monomer (TAT) to formulate nt-TiO2:TAT, which were characterized by transmission electron microscopy (TEM). The nt-TiO2, TAT, and nt-TiO2:TAT were evaluated via Fourier Transform Infrared, Ultraviolet–visible, and micro-Raman spectroscopies. An experimental adhesive resin was formulated with bisphenol A glycerolate dimethacrylates, 2-hydroxyethyl methacrylate, and photoinitiator/co-initiator system. nt-TiO2 or nt-TiO2:TAT were incorporated at 2.5 wt.% and 5 wt.% in the adhesive. The base resin without nt-TiO2 or nt-TiO2:TAT was used as a control group. The adhesives were evaluated for antibacterial activity, cytotoxicity, polymerization kinetics, degree of conversion (DC), Knoop hardness, softening in solvent (ΔKHN%), ultimate tensile strength (UTS), 24 h- and 1 year- microtensile bond strength (μ-TBS). Results TEM confirmed the nanotubular morphology of TiO2. FTIR, UV–vis, and micro-Raman analyses showed the characteristic peaks of each material, indicating the impregnation of TAT in the nt-TiO2. Adhesives with nt-TiO2:TAT showed antimicrobial activity against biofilm formation compared to control (p 0.05). All groups showed high percentages of pulp cell viability. The polymerization kinetics varied among groups, but all presented DC above 50%. The addition of 5 wt.% of nt-TiO2 and both groups containing nt-TiO2:TAT showed higher values ​​of Knoop hardness compared to the control (p Significance The mixing of a triazine-methacrylate monomer with the nt-TiO2 generated a filler that improved the physicochemical properties of the adhesive resins and provided antibacterial activity, which could assist in preventing carious lesions around tooth-resin interfaces. The set of physical, chemical, and biological properties of the formulated polymer, together with the greater stability of the bond strength over time, make nt-TiO2:TAT a promising filler for dental adhesive resins.

In understanding the catalytic efficacy of silver (Ag0) and gold (Au0) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO2–MgO–Al2O3–B2O3–K2O–MgF2 system is studied. The thermal parameters viz., glass transition temperature (Tg) and crystallization temperature (Tc) were extensively changed by varying NPs (in situ or ex situ). Tc was found to be increased (Tc = 870–875 °C) by 90–110 °C when ex situ NPs were present in the glass system. Under controlled heat-treatment at 950 ± 10 °C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, [KMg3(AlSi3O10)F2]. Along with the secondary phase enstatite (MgSiO3), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (∼50–400 nm) has been observed through FESEM in in situ doped GCs. An ex situ Ag doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1–3 μm ensured its superior machinability. Vicker's and Knoop microhardness of in situ doped GCs were estimated within the range 4.45–4.61 GPa which is reduced to 4.21–4.34 GPa in the ex situ Ag system. Machinability of GCs was found to be in the order, ex situ Ag > ex situ Au ∼ in situ Ag > in situ Au. Thus, the ex situ Ag/Au doped SiO2–MgO–Al2O3–B2O3–K2O–MgF2 GC has potential for use as a machinable glass-ceramic.

Purpose To seek a simple solution that can recycle and regenerate dental CAD/CAM zirconia green blanks from its waste residuals. Methods Waste residuals (3M® Lava™ Plus HT) were pulverized after dry milling and cutting, and subsequently sieved before pickling in a 0.5 M nitric acid. These powders were then dry-pressed and pre-sintered into blocks at seven different temperatures in the range 800-1100 °C. New zirconia blocks flagged with the same batch numbers were used as control. These blocks were cut into bars before subjected them to manufacturer-recommended sintering at 1450 °C. Crystalline phases (by XRD), elemental compositions (by EDX), surface morphologies (by SEM), machinability, linear shrinkage rate, relative density, and Knoop microhardness were evaluated before and after sintering, and four-point flexural strengths were also evaluated for the sintered zirconia bars. Results Only tetragonal phases were found in both pre- and fully-sintered recycled zirconia blocks. SEM results showed that pre-sintered samples at 950 °C had smooth and flat surfaces with evenly distributed particles. Recycled and control zirconia blocks had similar elemental compositions. Results from machined surface, linear shrinkage rate, relative density, and Knoop microhardness established that 950 °C and 1000 °C were suitable pre-sintering temperatures for recycling zirconia. Pre-sintered recycled zirconia had no significant differences in flexural strengths, however, samples pre-sintered at 1000 °C exhibited the closest value (897 MPa) compared to that of the control (904 MPa). Conclusions Dental CAD/CAM zirconia can be recycled and reused from its waste residuals by adopting a simple method that requires a pre-sintering at 950 or 1000 °C.

Objective The role of toothpaste used during aesthetic treatments is rarely investigated. The objective was to evaluate the effects of a bioactive glass-based toothpaste (BGT) used before or after the dental bleaching with 35% hydrogen peroxide (HP). Materials and Methods Bovine enamel blocks (4 × 4 mm; n = 12) were submitted to tooth bleaching and different treatments/storage, before or after HP, based on: (1) no toothpaste and immersion in artificial saliva (AS) after HP for 24 hours, 7 days, or 14 days (control); (2) daily BGT use and AS storage for 7 or 14 days (after HP); and (3) daily BGT use and AS storage for 7 or 14 days (prior to HP). Surface and in-depth color were determined using the CIE L*a*b* system (ΔL*, Δa*, Δb*, and ΔE) on enamel surface and underlying dentin. The surface microhardness (SMH) was evaluated using a Knoop microhardness tester. Statistical Analysis Data were submitted to analysis of variance (ANOVA) (color variables), repeated measures ANOVA (SMH), and Tukey’s test (α = 0.05). Results The color changes on the enamel or underlying dentin were not statistically different among the groups (p > 0.05). Twenty-four hours after HP presented a decrease in SMH differing from baseline (p < 0.01). This decrease did not occur in the groups previously exposed to BGT (p > 0.05). BGT use after HP for 7 days differed from group with exclusive AS storage (p < 0.05). Conclusion In-office tooth bleaching can decrease the microhardness of enamel surface; however, the use of BGT promotes the protection or enables the mineral recovery of tooth without the influence the bleaching efficacy.

Background: Teeth in the human body are the most mineralized tissue, which contain both organic and inorganic components. Demineralization and remineralization of teeth occur continuously, but demineralization causes structural loss of a tooth. Aim: This study was done to find the effect of ceramic by adding mono-n-Dodecyl phosphate to ceramic in dentin remineralization. Materials and Methods: A total of sixty permanent intact tooth specimens were randomly divided into four equal groups: Group 1: control group, Group 2: dentin was etched and restored with plain ceramic restoration, Group 3: etched dentin restored with ceramic containing 2% mono-n-Dodecyl phosphate, and Group 4: etched dentin restored with ceramic containing 5% mono-n-Dodecyl phosphate. Each sample was immersed completely in simulated body fluid and was kept in an incubator at 37°C to simulate the human body environment. Knoop microhardness measurements were recorded at 10, 20, and 38 days. Results: Knoop microhardness of dentin (KHN) reduced to 32.6% after dentin was etched. No significant difference was found between group 2, 3 and 4 after 10 days. KHN value was increased and showed significant changes restored with group 2 and 3, group 3 showed nonsignificant changes. Conclusion: Through this study, we found that Ceramic can be used as a remineralizing agent to restore marginal dentine around of the cavity and root lesions from secondary caries.

Purpose This study investigated the influence of professional mechanical tooth cleaning (PMTC) pastes on the surface texture of different subject materials. Methods Two one-step PMTC pastes, Clinpro Cleaning Paste for PMTC (CP) and PRG Pro-Care Gel (PG), and multiple-step PMTC pastes, Merssage Regular (MR), Merssagge Fine (MF), and Merssage Plus (MP), were used. For comparison, PMTC was performed using distilled water without paste (DW). The subjected materials used were bovine enamel (ENA) and dentin (DEN), a resin composite (FSU), and lithium disilicate (IEC). The prepared specimens were polished using a #2000-grit silicon carbide paper. PMTC was performed using a brush at 1,000 rpm for 15 s. Results The surface roughness (Ra) values of the specimens before and after PMTC were measured by laser scanning microscopy. The Knoop hardness number (KHN) of the subjected material was obtained. The types of PMTC pastes and subject materials had a significant influence on the Ra values and KHN. For the majority of subject materials, the descending order of Ra values after PMTC was MR > MF > CP > PG > MP > DW. The descending order of KHN of the materials was IEC > ENA > FSU > DEN. Conclusion Although one-step PMTC pastes appeared to be effective, it is important to consider the subject material during PMTC.

Background To assess whether glass-ceramic shade, thickness and translucency affect degree of conversion (DC) and Knoop microhardness (KHN) of resin cements photoactivated using light-emitting diode (LED) or quartz-tungsten-halogen (QTH) units. Material and Methods Glass-ceramic blocks were cut (2, 3 and 4mm) and sintered. For DC FT Raman spectroscopy (n=3), film specimens of cements (RelyX ARC, U200, Veneer, C&B) were obtained. For KHN test (n=3), cements were inserted in cylindrical matrix and covered by polyester strip. Specimens were photoactivated (30s) using LED or QTH according to each group: direct photoactivation (DP), interposing ceramic specimens or no photoactivation (NP). Data were analysed by ANOVA and Tukey’s test, Kruskal-Wallis and Dunn’s tests (p

Objectives: The aim of this research was to evaluate the effect of long-term use of three intracanal medicaments on the radicular dentin microhardness and fracture resistance. Material and methods: A chemomechanical preparation was done using the Protaper rotary instruments up to F3. The teeth were stored in an incubator at 37°C at 100% humidity and were categorized in three groups by random allocation, namely: Triple Antibiotic Paste (TAP), Calcium hydroxide paste (Apexcal) and Ledermix. Following medicament application, the access openings of all teeth were sealed with 4 mm thickness of cavit. The samples were stored for periods of 1 week, 1 month and 3months. Two dentin cylinders measuring 5mm and 3mm were obtained from each sample. The cervical third was used for fracture resistance and the middle third was used for micro hardness evaluation. The microhardness testing was done using a Knoop microhardness tester, and the fracture resistance testing was done using the universal testing machine. Results: Calcium hydroxide showed maximally negative effect on the physical properties of radicular dentin compared to TAP (p= 0.0100 at one month and Ledermix (p=0.0001 at one month ). With an increase in the application time, there was an increased deterioration in the physical properties of radicular dentin. Conclusion: Long-term placement of calcium hydroxide, Triple Antibiotic Paste, and Ledermix (p= 0.0001at 3 months) significantly affects the microhardness and fracture resistance of radicular dentin.

PURPOSE To measure the chemical composition, Knoop hardness, surface roughness, and composite bond strength of additive manufactured (AM) and conventional interim materials. MATERIAL AND METHODS Disks were prepared using conventionally (CNV group) and additively manufactured (AM group) materials: CNV-1 (Protemp 4; 3M ESPE), CNV-2 (Anaxdent new outline dentin; Anaxdent), AM-1 (FreePrint temp; Detax), AM-2 (E-Dent 400 CB Envisiontec), AM-3 (NextDent CB 3D Systems), and AM-4 (Med620 VEROGlaze; Stratasys). Each group was subdivided into 3 subgroups (n = 20) for analyzing Knoop hardness (KHN), chemical composition, superficial roughness (Ra), and composite shear bond strength. The first subgroup was exposed to a microhardness test. Subsequently, EDAX analysis was selected to analyze the chemical composition. The second subgroup was selected to measure the superficial roughness (Ra) using a contact profilometer. The third subgroup was used to measured composite shear bond strength using a universal testing apparatus. A digital microscope was used to analyze the fracture mode. The Shapiro-Wilk test showed normally distributed data. One-way ANOVA and post hoc Sidak tests were selected (α = 0.05). RESULTS Major variances in chemical composition were observed among the specimens. Significant differences in Knoop hardness (p < 0.001) and surface roughness (p < 0.001) were detected. The AM-4 (13.45 ± 2.93 KHN), the CNV-2 (13.35 ± 5.84 KHN), the AM-2 (13.03 ± 3.29 KHN), and the AM-1 (12.55 ± 2.93 KHN) groups obtained the highest Knoop hardness values, followed by the AM-3 and the CNV-1 groups (p < 0.05). The AM-1 group (1.88 ± 1.11 Ra) obtained the highest surface roughness values among the groups, followed by the AM-3 group (0.90 ± 0.14 Ra) (p < 0.05). However, no significant differences in shear bond strength values were found between the groups ranging from 23.18 ± 8.88 MPa to 33.29 ± 9.17 MPa (p = 0.061). All the groups showed a cohesive mode of failure. CONCLUSIONS The AM interim materials tested had significant chemical composition variations compared to conventional materials. For the mechanical properties evaluated, the AM materials obtained appropriate mechanical properties for use as an interim dental restoration. However, further studies are required to evaluate more extensively its mechanical properties and verify their applicability in the oral cavity, clinical behavior, and biocompatibility.

Made available in DSpace on 2021-06-25T11:06:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 This study evaluated the efficacy of S-PRG vanishes on preventing enamel demineralization. Bovine enamel specimens were obtained, polished and the baseline Knoop microhardness was evaluated. Specimens were stratified into six groups (n = 15), according to the varnish applied: S10—experimental varnish containing 10% of S-PRG fillers, S20—20% of S-PRG fillers, S30—30% of S-PRG fillers; S40—40% of S-PRG fillers; PC (positive control)—5% of NaF; NC (negative control)—no treatment was performed. Half of enamel surfaces were protected to work as a control and varnishes were applied over the unprotected area. A demineralizing pH-cycling was performed, and surface and cross-sectional microhardness were measured. The percentage of microhardness of the treated area was calculated comparing with the untreated area. Statistical analysis was performed by one-way ANOVA and Tukey’s test (p = 5%). All experimental S-PRG varnishes protected against demineralization in relation to no treatment, but S40 was the most effective on the surface. For all depths, S30 and S40 were superior in enamel demineralization prevention than other S-PRG filler concentrations and 5% NaF. It was concluded that S-RPG filler containing varnishes were effective to prevent enamel demineralization. The higher concentrated products were more effective than 5% sodium fluoride on surface demineralization prevention. Department of Restorative Dentistry São Paulo State University - UNESP Institute of Science and Technology, Av. Eng. Francisco Jose Longo, 777 Department of Dental Materials and Prosthodontics São Paulo State University - UNESP Institute of Science and Technology, Av. Eng. Francisco Jose Longo, 777 Department of Research and Development Shofu Inc., 11 Kamitakamatsu-cho, Fukuine, Higashiyama-ku Department of Restorative Dentistry São Paulo State University - UNESP Institute of Science and Technology, Av. Eng. Francisco Jose Longo, 777 Department of Dental Materials and Prosthodontics São Paulo State University - UNESP Institute of Science and Technology, Av. Eng. Francisco Jose Longo, 777

The structural, mechanical, and electrophysical properties of Al–B, Al–B–C, and Al–B–Si–C coatings obtained by dual magnetron sputtering of AlB2, SiC, and graphite targets are studied. During deposition, the current applied to the AlB2-containing target (IAlB) is used as a main variable parameter. Deposited coatings are characterized by X-ray diffraction, infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Knoop microhardness tests, and current–voltage characteristic measurements. It is established that all the deposited coatings are X-ray amorphous materials. The FTIR and XPS results show that the B–B, Al–B, B–O, and Al–O bonds are main bonds in all the deposited coatings. Dual sputtering of targets with AlB2 and C, and AlB2 and SiC gives rise to the formation of additional B–C, Si–C, and C–C main bonds in the deposited coatings. It is found the coatings are strengthened with an increase in the IAlB current as a result of increasing the number of B–B and Al–B bonds. The current–voltage characteristics of Al–B and Al–B–C coatings indicate that the coatings are disordered semiconductors in which the hopping conduction mechanism operates.

The prosthetic materials used in dentistry can generally be classified into different categories as measurement, restorative, cements and soft liner materials. Different tests are used in the measurement of the resistance and surface properties of these materials. The aim of this study was to given information about mechanical properties of materials, mechanical tests, test are used evaluated the surface hardness and roughness. Mechanical tests involve shear, micro-shear, tensile, micro-tensile, shear-tensile, torsion, compression, fatigue strength and flexure tests. Hardness tests are Brinell, Vickers, Knoop, Rockwell, Shore A and Barcol tests. Surface roughness tests are conducted using profilometers, scanner electron microscope and atomic force microscope. In addition, the internal structure of the materials is also tested by doing absorption and coloring tests. With the mechanical tests, the durability of the materials under the chewing pressure is measured, and with the surface roughness tests, measures are taken for the irritation of the oral tissues. Various in vitro tests are required to evaluate the materials used in the oral environment.

Introduction Provisional restoration is a critical component of fixed prosthodontics treatment, which must satisfy many inter-relative factors such as biological, mechanical, and esthetic. These restorations should have accurate marginal adaptation and optimum strength to maintain functional demands. The present “in vitro” study was conducted to evaluate the effect of water temperature and duration of immersion, on the marginal adaptation and microhardness of four different commercially available provisional restorative materials. Materials and Methods The 240 specimens were then seated on the stainless-steel die which simulated the prepared tooth, and evaluated for the marginal gap for four different provisional restorative materials and divided into four different groups A, B, C, and D. Each group was further divided into six subgroups according to temperature of water and time of immersion. In each group the samples were immersed in water at 20, 30, and 40 degrees, respectively for 5 and 10-minutes duration. Four different temporary restorative materials for crown fabrication were loaded each time to make temporary crowns. Results Each sample was placed under travelling stereoscopic microscope (20× magnification) and photographed. Results for each surface were obtained, and the average of three surfaces was calculated. Knoop hardness was measured using a microhardness tester. The study was subjected to statistical analysis, to know the statistical significance, of the effect of difference in time and temperature changes at the time of final polymerization on surface microhardness and marginal integrity of four different provisional restorative materials. Discussion The mean marginal discrepancies of bis-GMA (group B) at 20, 30, and 40°C for 5 and 10 minutes in water were smaller than the results of other groups. Microhardness evaluation showed that the poly ethyl methacrylate (PEMA) type resin exhibited significantly lower microhardness than the bis-acryl resin composites (Protemp 4 and Systemp.c&b) at both time and temperature intervals. Conclusion The bis-acryl composites material has the least marginal discrepancy in comparison with PEMA and polymethyl methacrylate (PMMA). The bis-acryl composites materials exhibit superior surface microhardness followed by PEMA and PMMA.

A method for evaluating residual stress using an instrumented indentation test was developed some decades ago. More recently, another method was developed, using a Knoop indenter. The conversion factor ratio, which is one of the key factors in the evaluation algorithm, has been taken to be 0.34, although this value comes from an experimental result and its physical meaning has not been examined. Here we examine the physical meaning of this conversion factor from the previous residual stress model, and calculate its ratio using analytical model of the stress field beneath the indenter. In this process, we assumed that the conversion factor ratio was the ratio of the projected area of the plastic zone generated during the Knoop indentation test. An analysis of the stress field beneath the indenter was performed by FE simulation. Actual nanoindentation was conducted after Knoop indentation testing, using the interface-bonding technique, to identify the plastic zone. In addition, the conversion factor ratio was also calculated for the case where residual stress was present, and the geometric ratio of the Knoop indenter was different. A comparison of our results with those from previous studies showed that the conversion factor ratio obtained using our assumption was in good agreement with previous studies. (Received May 20, 2020; Accepted June 15, 2020)

The aim of this study was to investigate the detailed macro/microstructures of three different surface coating technologies on the 6082-T6 aluminum alloy surface, namely Plasma Electrolytic Oxidation (PEO), Hard Anodizing (HA), and Plasma Spray Ceramic (PSC). Some of the PEO coatings were sealed with silicates. The microstructure investigations were performed using optical microscope, scanning electron microscope equipped with EDX analyzer and X-ray diffractometer. The microhardness of the base material and the coated layer were evaluated using Knoop indenter. All the coated layers appeared as two different layers. The PSC coating was the thicker followed by HA then PEO coating. The HA coating had irregular surface appearance, contained some cracks and appeared as an amorphous structure. The PSC coating was loose and had a poor bond with the substrate. The structure of PSC coating exhibited a lamellar geometry configuring 14% α-Al2O3 and 86% γ-Al2O3. The presence of porosity and voids was also observed. The PEO coatings were uniform and comprehensive. It adhered quite well to the substrate consisting of alumina (α and γ) phases. The ratio of γ alumina to α alumina was 79:31%. The sealed PEO coating with silicate had much lower porosity especially in the outer layer. All the coatings exhibited higher hardness than the substrate. The PEO coating showed the highest hardness compared with other coatings. The hardness of the PEO coating improved as the readings were taken away from the base. It displayed a maximum value in the middle and then started to reduce. The PSC coating has the highest roughness value followed by HA and then PEO coatings.

Active metal brazing of SiC-base ceramics and composites to Ti, Cu-clad-Mo, and nickel was carried out to screen promising commercial braze compositions with liquidus temperatures of 810-1040 °C. Microstructure, elemental composition, and microhardness were characterized using FESEM, EDS, and Knoop test in joints brazed using Ag-Cu-Ti alloys (Cusil-ABA and Ticusil) and a Ni-base alloy (MBF-20). Ti- and Si-rich interfacial layers developed in joints brazed using Ti-containing brazes, whereas Ni- and Si-rich layers formed in joints brazed using Ni-base brazes. Monolithic SiC/Mo and SiC/Kovar joints with Cusil-ABA had sound interfaces and compressive shear strengths of 25-30 MPa. In the case of composites, surface preparation influenced bond quality: ground SiC-SiC samples led to sound joints and unground samples led to interfacial decohesion at low thermal strains whereas joints cracked regardless of the surface preparation at large thermal strains. Among SiC-SiC/metal joints, SiC-SiC/Cu-clad-Mo had the best microstructure and bond quality. Microstructures of joints made using MBF-20 mixed with low-expansion Si-X (X: Y, Ta, Hf, Ti, B) eutectic powders to control the thermal expansion are also presented.

The water sorption and solubility of two polymer resin‐based dental composite materials were assessed in order to evaluate the effects of immediate post‐cure water exposure on the water sensitivity of the composites. Each material was tested with two different light curing setups. The radiant exposure of the two curing setups differed by a factor of 5. After exposure to water and subsequent drying, the Knoop surface hardness was measured. The change in the degree of conversion in both water and air storage medium within the first 24 h after curing was monitored by Raman spectroscopy. No significant differences in the degree of conversion were detected 24 h after curing. Samples exposed to the lower irradiation dose showed higher solubility and a lower surface hardness than the samples exposed to the higher irradiation dose. Early exposure to water did not cause detectable differences in the ongoing polymerization process. Increase in radiant exposure reduced the fraction of unbound constituents and increased the crosslink density, thereby reducing the plasticity of the material.

The influence of density on the hardness value of β-SiC samples was studied based on Knoop and Vickers indentation tests. Hardness measurements were performed on additive-free spark plasma sintered SiC samples in the [80%–95%] density range and on highly dense samples (>99%) sintered with very low content of sintering aids. Results revealed that the density has a strong influence on the hardness value, which increases of about 7 GPa between samples presenting densities of 80% and 95% and even reaches 21 GPa under 2 kg with Knoop indenter for the densest samples sintered with very low content of sintering aids. These results allowed us to give a comprehensive model-supported analysis of the mechanical properties of spark plasma sintered β-SiC with controlled porosity that currently does not exist in the literature. The calculation of Young modulus and toughness further resulted in encouraging properties for our samples with regards to mechanical and ballistic performances.

The impact of the microstructural properties of alumina on its mechanical properties is examined in this study. Furthermore, a comparison of the mechanical behaviours of alumina samples obtained by two-step and existing sintering techniques is presented. The results are rationalised by evaluating the changes in the densities and grain sizes of alumina samples. Different two-step treatments were used on commercial alumina (99.7 mass%-Al2O3 content, 0.73 μm average particle size) and compared with the existing sintering technique. Alumina powder was formed by uniaxial pressing, and the samples were treated using heat. Microstructural analyses of the samples were performed with a scanning electron microscope. The mean grain size was determined via the intercept method. Porosity was determined by the relationship between the apparent and theoretical densities of the sintered alumina. The bending strength test was performed based on ASTM 1161–13. Fracture toughness was measured based on the notch method. The microhardness test was performed using the Knoop technique. The results showed that mechanical properties of the samples prepared using two-step sintering were improved—the bending strength, fracture toughness, and Knoop microhardness increased from 286 to 303 MPa, 4.09–4.35 MPa m0.5, and 17.5–17.6 GPa, respectively—compared with those fabricated using the existing sintering technique, even with a higher porosity of 2.36% in samples obtained by two-step sintering and 1.80% in the existing sintering technique. Factorial analysis demonstrated that the temperature and holding time of the second step individually affect the relative density; however, the impact of temperature is more significant. Despite this, the interaction between temperature and holding time of the second step has the most significant impact on the average grain size.

A series of phosphate glasses composed of (65-x)P2O5–15BaO–5Al2O3–5ZnO–10Na2O-xB2O3 (x = 0, 2, 4, 6, and 8 mol%) were successfully prepared using the melt-quenching method. The effects of the addition of boron trioxide (B2O3) on the physical, structural, and mechanical properties of the glasses were investigated. As the added content of B2O3 increased from 0 to 6 mol%, the glass exhibited increased density and transition temperature, and decreased molar volume, indicating optimization of the glass stability. Raman spectroscopy revealed that the introduction of B2O3 transformed the glass from a chain structure to a three-dimensional network structure, which enhanced the chemical stability of the glass by the cross-linking of long phosphate chains with boron ions. Regarding the mechanical properties, when the boron content was 6 mol%, the flexural strength of the glass was 41% higher than that of the undoped boron, while the Vickers hardness and Knoop hardness values increased by 20.58% and 7.05%, respectively, and the fracture toughness was slightly decreased. In general, improving the mechanical properties of phosphate glass is of great significance for increasing the applications of this glass.

The elastic modulus and hardness of a cold-sprayed Al-25Zn metal matrix composite were characterized with the aid of Knoop and Vickers microindentation tests, nanoindentation test, and resonance frequency (RF) analysis. The mechanical properties were compared with the predictions of object-oriented image-based finite element (FE) analysis and related to the microstructural characteristics revealed by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The cold-sprayed coating exhibited an isotropic behavior along transversal and longitudinal directions and the predicted elastic modulus closely matched the results from the nanoindentation test. The approach offers a solution to the challenging task to determine the elastic modulus of thin coatings.

Background In this study was evaluated the effect of carbamide peroxide (CP) and hydrogen peroxide (HP) in different concentrations on hardness, roughness, and color parameters (color change - ΔE, lightness - ΔL, and yellow-blue axis - Δb) of bovine teeth. Material and methods Fifty square dental blocks (7 x 7 x 2 mm) were submitted to initial readings of Knoop hardness, surface roughness (Ra), and color parameters. Specimens were divided into 5 groups (n = 10): control group was kept in artificial saliva during the experimental period; CP 20% was bleached for 2 h daily for 14 days, HP 9.5% was bleached for 30 min daily for 14 days, HP 38% the bleaching gel was applied for 15 min, gel was removed and it was reapplied for two more times, the bleaching session was repeated for another 2 times every 7 days, totaling three sessions, and in CP 45% three sessions of 30 min each were performed of 7 in 7 days. All groups after the bleaching procedures had the bleaching gel removed, washed, and kept in artificial saliva. At the end of bleaching treatment, the hardness, roughness, and color parameters (ΔE, ΔL, and Δb) were re-evaluated. Data were analyzed by ANOVA, Tukey, and Dunnett tests (α = 0.05). Results Bleaching promoted a reduction in hardness, the CP 45% showed the lowest hardness and the CP 20% the highest, the HP 9.5% and HP 38% showed intermediate values of hardness. Bleaching agents did not affect the roughness. CP 20% and HP 38% promoted the highest values of ΔE and higher reduction of yellowish tone of tooth. Lightness increase after bleaching treatment for all groups. Conclusions All the bleaching agents tested showed effectiveness, but with reduced hardness. Key words:Carbamide peroxide, hydrogen peroxide, tooth whitening, hardness, roughness.

Marbles are secondary decomposition products formed by metamorphism of limestone. Effective classification of marble quarries in terms of quality enables the selection of a sustainable production method and safety application. This evaluation is based on physico-mechanical properties of the samples. Obtained results of physico-mechanical properties of the marbles were statistically analyzed using Stata 14 and SPSS 21 software. The marbles indicated mostly normal physical and mechanical properties. A strong inverse relationship exists between Abrasion Value and Knoop Hardness Determination that indicates a significant nonlinear relationship. Samples were distinguished into 3 groups of close similarity and related properties. The estimated value of the parameters is in the 95 % confidence interval. The equation obtained by regression analysis was used for the determination of resistance to abrasion.

AIM Simulated pulpal pressure (PP) has been shown to affect the bond strength and nanoleakage of different adhesives at dentin interfaces but the effect of simulated PP on polymerization of adhesives has not been studied yet. Furthermore, it has been proposed that strong and mild self-etch adhesives have different polymerization behaviors. This study aimed to evaluate the effect of simulated PP on polymerization of two self-etch adhesives, Adper Prompt L-Pop (APLP) and Adper Easy Bond (AEB), by means of the Knoop hardness test. MATERIALS AND METHODS Sixty caries-free human molars were used to prepare deep dentin specimens with a mean remaining dentin thickness of 0.9 mm. The specimens were bonded in the absence or presence of PP. The specimens were assigned to four equal groups (n = 15) as follows: AEB/-PP, APLP/-PP, AEB/+PP, and APLP/+PP. Bonding procedures were completed; then the specimens' hardness was measured with the Knoop test. Data were analyzed with two-way ANOVA and the t test. RESULTS In the absence of PP, the hardness of AEB was significantly higher than that of APLP (p < 0.001). In contrast, when PP was simulated, the hardness of APLP was higher than that of AEB (p = 0.002). The hardness of AEB was not influenced by the presence of PP (p = 0.153). Simulation of PP resulted in a significant improvement in the hardness of APLP (p < 0.001). CONCLUSION The polymerization degree of strong self-etch adhesive was lower compared to mild self-etch adhesive. In the presence of hydrostatic PP, the polymerization degree of strong self-etch adhesive was higher than mild self-etch adhesive. CLINICAL SIGNIFICANCE Dentin moisture caused by positive PP might improve polymerization of strong self-etch adhesives.

Background This study aimed to evaluate the X-linked hypophosphatemic rickets (XLHR)-related compositional and microhardness tooth aspects. Material and Methods One affected and one non-affected teeth by XLHR were sectioned transversely, and each section was separated for Micro-Raman spectroscopy, Knoop microhardness and scanning electron microscopy with energy dispersive x-ray microanalysis (SEM-EDS). The outcomes of these analyses were assessed. Results Outcomes of Raman analysis of inorganic/organic components (~958/~1250+~1450 cm−1) and carbonate/phosphate (~1070/~958 cm−1) ratios showed areas of altered enamel and dentin (interglobular dentin, calcospherites, and mantle dentin) with an increase of inorganic content in the rickets tooth. Microhardness reduction was observed in the affected tooth, with a more evident drop in regions of mantle dentin, interglobular dentin, and calcospherites. SEM-EDS analysis showed demonstrated the absence of calcium and phosphorus in interglobular spaces. Conclusions In conclusion, compositional and structural deficiencies were observed in deciduous tooth affected by XLHR. Also, it was observed the absence of hydroxyapatite in the interglobular dentin by using Raman spectroscopy analysis. Key words:Dentin, dentin permeability, X-linked hypophosphatemic rickets, tooth, tooth calcification, Raman spectroscopy.

Exposure to hand-arm vibration (HAV) among the labor force in the mining industry can result in permanent vibration diseases such as behavioral disorders, visual impairment, osteoporosis, pain (mostly in the hands, wrists, and shoulders), circulatory system disorders, and malnutrition. In this study, the vibration exposure of excavator operators working regularly in 25 different natural stone quarries was measured. In addition, the relationship between vibration exposure and rock properties was investigated. Gloved and ungloved vibration measurements were performed and revealed that antivibration gloves reduce excavator operators’ vibration exposure by 7.10–25.95%. Samples from each quarry were characterized with rock mechanics tests. The correlations between the hand-arm vibration measurements and the natural stone physical–mechanical properties (uniaxial compressive strength, Shore hardness, Knoop hardness, apparent density and total porosity) were determined to be over 70%. One finding of the study was that the health risk in excavators cannot be reduced sufficiently by the sole use of antivibration gloves. Furthermore, the excavation of any rock with a Knoop hardness above 121 is associated with an 81% risk of HAV. To increase awareness of the danger of vibration exposure for natural stone miners, training programs should be provided, and technical and operational changes should be implemented.

This paper explores the fracture behavior of niobium carbides of varying compositions between NbC1.0 and NbC0.5. The surface crack in flexure (SCF) method was used to evaluate the fracture toughness as a function of carbon concentration. Additionally, hardness measurements were conducted with a Knoop indenter, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phase content and microstructures. As the carbon content decreased, the hardness increased from 8 GPa for NbC1.0 to 12 GPa for NbC0.5 and the fracture toughness decreased from 2.5 MPa m to 0.44 MPa m . Notably, the NbC0.67 sample exhibited a secondary precipitate lath-like microstructure with the laths indexed to β-Nb2C and a KIC near 2 MPa m . Though similar lath like structures in tantalum carbides have been reported to yield a KIC of approximately 15 MPa m , the laths in these two materials have fundamentally different structures where bonding in the former is comprised of β-Nb2C and the latter of ζ-Ta4C3-x. This results in the observed different fracture properties, which can be explained through concepts of microstructural toughening.

Mechanical properties of covalent materials can be greatly enhanced with strategy of nanostructuring. For example, the nanotwinned diamond with an isotropic microstructure of interweaved nanotwins and interlocked nanograins shows unprecedented isotropic mechanical properties. How the anisotropic microstructure would impact on the mechanical properties of diamond has not been fully investigated. Here, we report the synthesis of diamond from superaligned multiwalled carbon nanotube films under high pressure and high temperature. Structural characterization reveals preferentially oriented diamond nanotwin bundles with an average twin thickness of ca. 2.9 nm, inherited from the directional nanotubes. This diamond exhibits extreme mechanical anisotropy correlated with its microstructure (e.g., the average Knoop hardness values measured with the major axis of the indenter perpendicular and parallel to nanotwin bundles are 233 ± 8 and 129 ± 9 GPa, respectively). Molecular dynamics simulation reveals that, in the direction perpendicular to the nanotwin bundles, the dense twin boundaries significantly hinder the motion of dislocations under indentation, while such a resistance is much weaker in the direction along the nanotwin bundles. Current work verifies the hardening effect in diamond via nanostructuring. In addition, the mechanical properties can be further tuned (anisotropy) with microstructure design and modification.

In this paper, a pragmatic technique has been developed to evaluate the erosion-corrosion behavior of three kinds of ZrN coatings (i.e., monolayer, multilayer, and gradient layers) which were deposited on AISI 420 martensitic stainless steel using an ion-assisted deposition technology. Among them, the monolayer coating refers to the coating with no change in composition and structure, the multilayer coating refers to the coating with alternating change of Zr/ZrN, and the gradient coating refers to the ZrN coating by increasing N2 partial pressure gradually. The morphology, composition, and microhardness of these ZrN coatings were examined by means of integrating the scanning electron microscopy (SEM), X-ray diffraction (XRD), and Knoop hardness measurements, while anodic polarization tests and salt fog spray tests in a simulated industrial environment have been performed to evaluate and identify the corrosion mechanisms of these coatings. The surface microhardness and corrosion resistance of the AISI420 martensitic stainless steel is found to be significantly improved by depositing the ion-assisted deposition ZrN coatings. The study indicates that the erosion-corrosion behavior in the slurry is the result of the synergistic effect of small-angle erosion and acid solution corrosion. Three ZrN coatings hinder the slurry erosion-corrosion behavior from two aspects (i.e., erosion resistance of small-angle particles as well as corrosion resistance of the substrate), thereby significantly improving the erosion-corrosion resistance of AISI 420 stainless steel. In addition, the ZrN gradient coatings show a much better erosion-corrosion resistance than that of the monolayer/multilayer ZrN coating because they have excellent crack resistance, bearing capacity, and electrochemical performance.