Reduction In Microhardness Research Articles

Re-evaluation of Microhardness of Mineral Trioxide Aggregate and Biodentine After Removal From Root Using Different Types of Solvents: An In Vitro Study.

Objective This study aimed to evaluate the effects of different solvents on the microhardness of mineral trioxide aggregate (MTA) and Biodentine, which are used in endodontic therapy for their biocompatibility and ability to create a hermetic seal. Methods A total of 150 extracted human single-rooted teeth were selected and sectioned into 4 mm slices. The samples were divided into two groups according to the material used: MTA and Biodentine. Then the samples were incubated at 37°C and 100% humidity for 28 days. After that, 15 MTA and Biodentinesampleseach were sent for microhardness test and the remaining samples were subdivided into four subgroups according to the solvent used, i.e., treated with normal saline, 5.25% sodium hypochlorite, 10% citric acid, or 40% hydrofluoric acid. The microhardness of the upper and lower surfaces of the samples was measured using a Vickers microhardness tester. Results The average microhardness values for Biodentine and MTA were found to be 74.4 HV and 69.9 HV, respectively. Treatment with sodium hypochlorite, citric acid, and hydrofluoric acid significantly reduced the microhardness of both materials. Hydrofluoric acid had the most pronounced effect, followed by citric acid and sodium hypochlorite. Statistical analysis using one-way analysis of variance (ANOVA) 'F' test showed highly significant differencesbetween the groups. Discussion The study demonstrated that solvents such as hydrofluoric acid, citric acid, and sodium hypochlorite effectively reduced the microhardness of MTA and Biodentine, facilitating their removal during retreatment. This reduction in microhardness is attributed to the chemical interactions of the solvents with the materials, leading to disintegration and reduced structural integrity. Conclusion Biodentine had greater microhardness compared to MTA, and hydroflouric acid reduced the microhardness to a greater extentcompared to other solvents.

Effects of online marketplace-sourced over-the-counter tooth whitening products on the colour, microhardness, and surface topography of enamel: an in vitro study

ObjectivesThis study compared the whitening effect, microhardness, and enamel surface alterations of over-the-counter (OTC) tooth bleaching products with those of a dentist-prescribed at-home bleaching agent.Materials and methodsThe products available on a popular online marketplace were comprehensively searched and then rated using a specific formula. The effects of the lowest-rated OTC agent (LRA) and the highest-rated OTC agent (HRA) were compared with those of a dentist-prescribed bleaching agent (DPA) on the enamel of extracted human teeth. The bleaching efficacy, post-bleaching microhardness changes, and morphological alterations were assessed by spectrophotometric analysis, Vickers hardness testing, and scanning electron microscopy (SEM) respectively. Statistical analyses included one-way ANOVA and post hoc tests, maintaining a significance level of P < 0.05.ResultsThe search of the online marketplace revealed 15 products. The LRA (Teeth Whitening Serum Gel, GEN, China) and the HRA (Bright White-Lovely Smile Premium Teeth Whitening strips, Ray of Smile, USA) were identified on the basis of their ranking. DPA resulted in significantly better tooth whitening than did LRA. The enamel microhardness was lower in the LRA treatment group (14.2%) than in the control and HRA treatment groups (8.84% and 7.26%, respectively). LRA also caused severe topographical alterations to the enamel.ConclusionCompared with the poorly rated product, the dentist-prescribed tooth bleaching product resulted in greater colour improvement, less microhardness reduction, and surface changes. The highest-rated product was comparable with the dentist-prescribed agent in this study.

Mechanical and tribological characterization of wire arc additively manufactured SS308L component

The mechanical and tribological characterization of stainless steel 308 L, which was fabricated using wire arc additive manufacturing (WAAM), is presented in this work. Longitudinal tensile samples extracted along the deposition direction depict higher tensile strength than the transverse tensile samples. The reduction in microhardness along the build direction is associated with the temperature fluctuations the metal undergoes in the WAAM process. Ball-on-disc wear tests were performed on specimens from the top, middle, and bottom parts of the build at loadings of 20 N, 25 N, and 30 N. Furthermore; the wear analysis results showed that the top portion had the most wear at the highest load, while the bottom portion experienced the least wear under the lowest load.

Assessment of the effect of experimental gel of pregabalin associated with 35% hydrogen peroxide bleaching on bovine dental enamel: an in vitro study.

To assess the effect of bleaching with gel of pregabalin associated with 35% hydrogen peroxide on the mechanical and chemical properties and ultramorphology of dental enamel. Thirty-six (36) specimens of bovine dental incisors were obtained and divided into three groups (n = 12), namely: CG = bleaching with 35% hydrogen peroxide; KFG = bleaching with 5% potassium nitrate and 2% sodium fluoride gel + 35% hydrogen peroxide; and PGG = bleaching with experimental gel of pregabalin + 35% hydrogen peroxide. The specimens were assessed with respect to Knoop microhardness, surface roughness, and colour change, before and after bleaching. They were also assessed using scanning electron microscopy and energy-dispersive spectroscopy after treatments. All groups exhibited an increase in surface roughness and a reduction in Knoop microhardness after the protocols. There was colour change in all groups, with no difference between them. In addition, there were changes in enamel morphology and non-significant loss of calcium and phosphorus. The experimental gel of pregabalin did not influence the action of 35% hydrogen peroxide, yielding results similar to those of the other groups assessed in all the parameters. Therefore, the gel of pregabalin can be an alternative for topical application on the surfaces of the teeth in association with bleaching treatments.

Effectiveness of chitosan nanoparticles, and novel chemical irrigants with surfactant on smear layer removal and microhardness alteration

ObjectiveThis current study was designed to compare and correlate between smear layer eradication and reduction in microhardness by natural 0.2%chitosan nanoparticles and novel chemical irrigants with surfactant at the apical root third. Materials and methodOne hundred and twenty straight single-rooted extracted lower premolars were decoronated and working length obtained with #10 K-file. Pro-taper rotary files were used till apical size F3. The canals were simultaneously flushed with assigned irrigant containing surfactant [(ChX-Ultra, NaOCl-Extra, Pro-EDTA, 0.2%chitosan nanoparticles, Biopure MTAD]. The samples were randomly divided into two equal groups (n = 60). InGroup S (n = 60), the residual smear layer was examined by scanning electron microscope and in Group M(n = 60) microhardness was determined by Vickers Microhardness Tester. Further both groups were divided into six equal groups (n = 10 each) according to assigned irrigating solutions.For smear layer removal; Kruskal-Wallis tests followed by pair wise comparison using Mann Whitney U test was done. For change in microhardness ANOVA and post hoc Tukey tests was done. ResultsMaximum smear layer removal was recorded in Biopure MTAD (1.8 ± 0.63), followed by pro-EDTA (2.2 0 ± 0.63) then 0.2%chitosan (2.6 ± 0.51), then NaOCL Extra (3.5 ± 0.53)and least in CHX-Ultra (4.4 ± 0.52) and saline (5.0 ± 0.00). Pro-EDTA group (12.8 ± 2.47) revealed significant highest reduction in microhardness followed by Biopure MTAD (8.01 ± 3.06), 0.2%chitosan nanoparticles (5.48 ± 2.87), NaOCl-Extra (5.44 ± 1.62) and least recorded in CHX-Ultra (4.94 ± 1.43) and saline (3.04 ± 0.63). ConclusionThe elimination of the smear layer is always accompanied by a reduction in microhardness. Moreover, irrigant with surfactant and chelators enhanced smear layer removal, with best perceived in Biopure MTAD.

The Effect of Interlayer Delay on the Heat Accumulation, Microstructures, and Properties in Laser Hot Wire Directed Energy Deposition of Ti-6Al-4V Single-Wall.

Laser hot wire directed energy deposition (LHW-DED) is a layer-by-layer additive manufacturing technique that permits the fabrication of large-scale Ti-6Al-4V (Ti64) components with a high deposition rate and has gained traction in the aerospace sector in recent years. However, one of the major challenges in LHW-DED Ti64 is heat accumulation, which affects the part quality, microstructure, and properties of as-built specimens. These issues require a comprehensive understanding of the layerwise heat-accumulation-driven process-structure-property relationship in as-deposited samples. In this study, a systematic investigation was performed by fabricating three Ti-6Al-4V single-wall specimens with distinct interlayer delays, i.e., 0, 120, and 300 s. The real-time acquisition of high-fidelity thermal data and high-resolution melt pool images were utilized to demonstrate a direct correlation between layerwise heat accumulation and melt pool dimensions. The results revealed that the maximum heat buildup temperature of the topmost layer decreased from 660 °C to 263 °C with an increase to a 300 s interlayer delay, allowing for better control of the melt pool dimensions, which then resulted in improved part accuracy. Furthermore, the investigation of the location-specific composition, microstructure, and mechanical properties demonstrated that heat buildup resulted in the coarsening of microstructures and, consequently, the reduction of micro-hardness with increasing height. Extending the delay by 120 s resulted in a 5% improvement in the mechanical properties, including an increase in the yield strength from 817 MPa to 859 MPa and the ultimate tensile strength from 914 MPa to 959 MPa. Cooling rates estimated at 900 °C using a one-dimensional thermal model based on a numerical method allowed us to establish the process-structure-property relationship for the wall specimens. The study provides deeper insight into the effect of heat buildup in LHW-DED and serves as a guide for tailoring the properties of as-deposited specimens by regulating interlayer delay.

Effect of butylated hydroxytoluene (BHT) concentrations on polymerization shrinkage stress and other physicochemical properties of experimental resin composites

The present study examined different concentrations of the butylated hydroxytoluene (BHT) inhibitor on the kinetics of conversion, polymerization shrinkage stress, and other correlated physicochemical properties of experimental resin composites (ERC). A model composite was formulated with 75 wt% filler containing 0.5 wt% camphorquinone and 1 wt% amine with BHT concentrations of 0.01 wt% (BHT-0.01); 0.1 wt% (BHT-0.1); 0.25 wt% (BHT-0.25); 0.5 wt% (BHT-0.5); 1 wt% (BHT-1), and control (no BHT). They were tested on polymerization shrinkage stress (PSS; n = 5), degree of conversion (DC; n = 3), maximum polymerization rate (RpMAX; n = 5), water sorption (Wsp; n = 0), and solubility (Wsl; n = 10), flexural strength (FS; n = 10), flexural modulus (FM; n = 10), Knoop microhardness (KH; n = 10), and microhardness reduction (HR; n = 10). Data concerning these tests were submitted to one-way ANOVA and Tukey's test (α = 0.05; β = 0.2). BHT-0.25, BHT-0.5, and BHT-1 showed a gradually significant decrease in PSS (p = 0.037); however, BHT-1 demonstrated a decrease in the physicochemical properties tested. Thus, within the limitations of this study, it was possible to conclude that BHT concentrations between 0.25 and 0.5 wt% are optimal for reducing shrinkage stress without affecting other physicochemical properties of ERCs.

Impact of calcium hydroxide and 2-hydroxyisocaproic acid on the microhardness of root dentine: an in vitro study.

To evaluate and compare the effect of calcium hydroxide [Ca(OH)2] and 2-hydroxyisocaproic acid (HICA) on the microhardness of root dentine. Fifty-one matured maxillary central incisors with straight root and type I canal configuration were decoronated to a standardized length of 16mm. The root canals were cleaned and shaped using rotary instruments up to size F5. The tooth samples were then randomly assigned into three groups (n = 17) based on the intracanal medicament placed. Group A: control group with no intracanal medicament, Group B: root canals placed with Ca(OH)2, and Group C: root canals placed with HICA. After 1week, the intracanal medicaments placed within the root canals were removed and the canals were dried. Subsequently, the specimens were split longitudinally into two halves and subjected to the Vickers microhardness test with indentations made at the coronal, middle, and apical-third root regions. The data were analyzed using one-way ANOVA and Tukey's post hoc tests. The control group showed significantly highest microhardness value (P < 0.001), followed by HICA and finally, Ca(OH)2 at the coronal, middle, and apical-third root regions, respectively. Nonetheless, there were no statistically significant differences in microhardness values across different root regions within each group. HICA was found to have a significantly lesser reduction in root dentine microhardness which could be a potential alternative to Ca(OH)2. Nevertheless, future studies are warranted to verify the present outcomes in the clinical setting.

Root Canal Dentin Microhardness after Contact with Antibiotic Medications: An In Vitro Study.

Background: Antibiotic pastes used as intracanal medication in cases of revascularization therapy might cause negative effects on tooth properties, such as a reduction in dentin microhardness. This in vitro study investigated dentin microhardness in three different locations distancing from the canal lumen after 20 days of treatment with a tri-antibiotic paste (ciprofloxacin, metronidazole, and minocycline), and with a double-antibiotic paste (ciprofloxacin and metronidazole), with calcium hydroxide [Ca(OH)2] UltracalTM XS-treated dentin as comparison. Material and Methods: Human mandibular premolars (n = 48) had the root canals cleaned and shaped and were used to produce dentin slices. Dentin slices remained immersed in the medications for 20 days. The Knoop microhardness (KHN) test was performed before (baseline/Day-0) and after treatment (Day-20) with the medications. Indentations were made at 25 µm, 50 µm, and 100 µm distances from the root canal lumen. The KHN was compared intra-group using Wilcoxon's test. Independent groups were compared using Mann-Whitney's and Kruskal-Wallis' tests, at α = 5%. Results: The microhardness in all the tested groups was reduced at Day-20 in comparison with Day-0 (p < 0.001) (intra-group comparison/same distances). The Day-0 values were similar, and the Day-20 values were higher for the Ca(OH)2 group (p < 0.05) (comparison between groups/same distances). Conclusions: Calcium hydroxide for 20 days would be preferred rather than antibiotic pastes to minimize the expected reduction in dentin microhardness during regenerative procedures.

Effect of Herbal Intracanal Medicaments on Microhardness of Root Dentin: An In Vitro Study.

The use of intracanal medicaments (ICM) is crucial toreduce the microbial load in root canals. However, its application may negatively affect the physical properties of root dentine. Thus, this in vitro study was performed to investigate the effects of different herbalICM on the microhardness ofroot dentin. A total of 100 mid-root discs were randomly divided into five groups (n = 20) and treated with Aloe vera, Aloe vera + chitosan, curcumin, curcumin + chitosan, and control for 14 days. A Vickers hardness indentation machine (Laizhou Laihua Testing Instrument Factory, Yantai, China) with a load of 200 g and a dwell time of 15 seconds was used for microhardness testing before andafter treatment. The results were analyzed usingStatistical Product and Service Solutions (SPSS, version 26.0; IBM SPSS Statistics for Windows, Armonk, NY). Intragroup comparisons were executed using paired t-tests, while intergroup comparisons employed ANOVA, followed by post-hoc Tukey's tests. The Aloe vera + chitosan and curcumin + chitosan groups showed a statistically significant reduction in dentin microhardness (p < 0.05). The decrease in dentin microhardness ofthe Aloe vera and curcumin groups was non-significant (p > 0.05) and similar to that of the control. Aloe vera or curcumin alone as ICM did not affect the root dentin microhardness. The addition of0.2% chitosan to either Aloe vera or curcumin negatively affected the root dentin microhardness.

Physico-chemical assessments of ion-doped bioactive glasses-based resin infiltrants

Bioactive glass-based resin infiltrants were developed to evaluate their chemo-physico-mechanical properties. Three methacrylate-based experimental resin infiltrants were synthesized using 45S5, fluoridated-bioactive glass (F-BG), and boron-bioactive glass (B-BG), whereby pure dimethacrylate resins and ICON® were used as a control infiltrants. The degree of conversion (DC), thermal analysis, and wettability were evaluated. In-vitro bioactivity test(s) and weight measurements were conducted in simulated body fluid for up to 28 days. The optical properties were analyzed in artificial saliva for up to 30 days. The micro-hardness and morphological changes were investigated following chemical aging. The experimental resin infiltrants displayed comparable DC, nearly equivalent wettability to ICON®. An apatite layer was formed on the surface of experimental samples; however, non-linear behavior was observed for weight measurement. Reduction in micro-hardness was observed with chemical aging. The optical properties of experimental infiltrants were better than ICON. The B-BG group showed more resistance to chemical aging and showed less changes during thermal analysis, as well as less loss of hardness. In contrast to other groups, the 45S5-based group showed greater in-vitro bioactivity. F- and B-ions in BGs showed a positive effect and potential to treat white spot lesions within the confines of this inquiry.

Assessment of multispecies biofilm growth on root canal dentin under different radiation therapy regimens.

To assess the growth of a multispecies biofilm on root canal dentin under different radiotherapy regimens. Sixty-three human root dentin cylinders were distributed into six groups. In three groups, no biofilm was formed (n = 3): NoRT) non-irradiated dentin; RT55) 55Gy; and RT70) 70Gy. In the other three groups (n = 18), a 21-day multispecies biofilm (Enterococcus faecalis, Streptococcus mutans, and Candida albicans) was formed in the canal: NoRT + Bio) non-irradiated + biofilm; RT55 + Bio) 55Gy + biofilm; and RT70 + Bio) 70Gy + biofilm. The biofilm was quantified (CFUs/mL). Biofilm microstructure was assessed under SEM. Microbial penetration into dentinal tubules was assessed under CLSM. For the biofilm biomass and dentin microhardness pre- and after biofilm growth assessments, 45 bovine dentin specimens were distributed into three groups (n = 15): NoRT) non-irradiated + biofilm; RT55 + Bio) 55Gy + biofilm; and RT70 + Bio) 70Gy + biofilm. Irradiated specimens (70Gy) had higher quantity of microorganisms than non-irradiated (p = .010). There was gradual increase in biofilm biomass from non-irradiated to 55Gy and 70Gy (p < .001). Irradiated specimens had greater reduction in microhardness after biofilm growth. Irradiated dentin led to the growth of a more complex and irregular biofilm. There was microbial penetration into the dentinal tubules, regardless of the radiation regimen. Radiotherapy increased the number of microorganisms and biofilm biomass and reduced dentin microhardness. Microbial penetration into dentinal tubules was noticeable. Cumulative and potentially irreversible side effects of radiotherapy affect biofilm growth on root dentin. These changes could compromise the success of endodontic treatment in oncological patients undergoing head and neck radiotherapy.

Effect of Different Irrigating Solutions on Root Canal Dentin Microhardness-A Systematic Review with Meta-Analysis.

The aim of this study was to evaluate the effect of different irrigating solutions as well as their combination and activation modes on root canal dentin microhardness. The protocol was registered in PROSPERO and PRISMA guidelines were followed. The structured question was as follows: "Which type of irrigating solution used in endodontic treatment causes more change in dentin microhardness?" The literature was screened via PubMed, Google Scholar, Scopus, and Science Direct. The last search was carried out in February 2023 with English language restriction. Two reviewers independently performed screening and evaluation of articles. A total of 470 articles were retrieved from all the databases, whereas only 114 articles were selected for full-text analysis. After applying eligibility criteria, 44 studies were evaluated and included in this review. The results showed that with increased contact time with irrigants, dentin microhardness decreases. Increased contact time with sodium hypochlorite (NaOCl) was associated with more reduction in dentin microhardness compared with other irrigants. Other irrigants, with the exception of distilled water, including EDTA, citric acid, herbal irrigants, glycolic acid, phytic acid, etc., in this study significantly decreased dentin microhardness. The maximum reduction in dentin microhardness was seen with 2.5% NaOCl after 15 min of contact time. The use of irrigating solutions alters the chemical composition of dentin, thereby decreasing its microhardness, which affects the clinical performance of endodontically treated teeth.

Comparative evaluation of microhardness of three restorative materials after immersion in chlorhexidine mouthwash: An in vitro study

Aim: To evaluate and compare the microhardness of Filtek Z250XT, Beautifil II, and Neo Spectra ST HV after immersion in chlorhexidine mouthwash. Materials and Methods: Thirty disc specimens (10 for each group) made of three different restorative materials, Group 1 – Filtek (3M ESPE), Group 2 – Beautifil II (Shofu), and Group 3 – Neo Spectra ST HV (Dentsply). To simulate 1 year of daily mouthwash use, 10 specimens from each group were immersed in chlorhexidine, kept in an incubator at 37°C for 12 h, and later subjected to microhardness measurement using Vicker’s hardness test. Finally, analysis of variance and post hoc tests were used to analyze the results statistically. Results: A significant reduction in microhardness was observed after immersion in chlorhexidine in Groups 1 and 3 compared to Group 2. Conclusions: Filtek Z250XT exhibits the highest microhardness compared to the other two materials. However, Beautifil II is more resistant to chlorhexidine mouthwash and does not show a significant reduction compared to the other two restorative materials.

Impact of various aging treatments on the microhardness and surface roughness of CAD-CAM monolithic restorative materials.

Dental ceramics deteriorate as a result of thermal aging and exposure to acidic solutions, which change their microhardness and surface roughness. This study assessed the resistance of several computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials in terms of surface roughness and microhardness following exposure to acidic solutions and thermal aging. Five different monolithic CAD-CAM restorative materials, two leucite-reinforced glass ceramics (G-Ceram and CEREC Blocs), a zirconia-infiltrated lithium silicate (Celtra Duo), a resin nanoceramic (Grandio), and monolithic zirconia (inCoris TZI), were used to create 2-mm-thick rectangular specimens (n = 100). After being immersed in either acidic saliva (pH = 4.0) (ST) or gastric juice (pH = 1.2) (GT), each material was subjected to 10,000 cycles of thermal aging. The Vickers microhardness and average surface roughness of the specimens were assessed at baseline, following thermal aging and exposure to either gastric juice or acidic saliva. The surface properties were examined using an atomic force microscope. The Mann‒Whitney U test with Bonferroni correction and the Wilcoxon signed-rank test was used for statistical analysis (a = 0.05). The surface roughness of two leucite-reinforced glass ceramics (G-ceram and CEREC) significantly decreased with ST (p = 0.027 and p = 0.044). Only the CEREC was affected when the aging protocols were compared, and the ST group had a significant reduction in roughness (p = 0.009). The microhardness values significantly decreased after both aging protocols in all groups except for the ST subgroup of G-Ceram. Only inCoris was affected when the aging protocols were compared, and the GT group exhibited a significant reduction in microhardness (p = 0.002). The surface roughness of the tested materials was not affected by the GT. Only leucite ceramics exhibited a decrease in surface roughness in the ST stage. Both aging processes produced a significant decrease in the microhardness of the tested ceramics. Leucite-reinforced glass-ceramic materials may be advantageous for patients with gastroesophageal reflux disease and those with a diet high in acidic foods due to their lower values for changes in microhardness and surface roughness compared to those of other CAD-CAM materials.

Comparative evaluation of effect of modified triple antibiotic paste and calcium hydroxide as intracanal medicament on microhardness of root dentin: An in vitro study

ABSTRACT Aim: To assess and compare the impact of modified triple antibiotic paste (MTAP) and calcium hydroxide (CH) as intracanal medicament on microhardness (MH) of root dentin. Materials and Methods: Twenty single-rooted, noncarious, single-canaled permanent teeth were selected. They were decoronated and vertically sectioned into two equal parts to acquire 40 samples. These samples were submerged in acrylic blocks with their pulpal surfaces exposed. These samples were enclosed within acrylic blocks, with their pulp surfaces visible. They were then randomly allocated into four groups (n = 10). MH was measured at three steps: initial measurement of MH before irrigation with 3% sodium hypochlorite (NaOCl); after irrigation with 3% NaOCl; and after interaction with medications (MTAP or CH pastes at an interval of 7 days or 30 days). The degree of reduction in MH percentage was computed. The collected data underwent statistical examination at a significance threshold of P &lt; 0.05. Results: All procedures led to a noteworthy decline in MH values when compared to both prior and initial measurement. The highest reduction in MH was seen after irrigation with 3% NaOCl (P &lt; 0.05). CH showed a greater reduction in MH as compared to MTAP (P &lt; 0.05). More reduction in MH was seen after 30 days as compared to that after 7 days for both CH and MTAP (P &lt; 0.05). Conclusion: Use of intracanal irrigants and medicaments reduces the MH of root dentin. Lesser reduction in MH was observed when utilization of MTAP as compared to CH.

Effects of a Benzalkonium Chloride Surfactant-Sodium Hypochlorite Combination on Microhardness and Mineral Content of Dentin

This study aimed to investigate the impact of the combination of Benzalkonium chloride (BAC) and sodium hypochloride (NaOCl) and its application after ethylenediaminetetraacetic acid (EDTA) in root canal irrigation procedures on the microhardness and mineral content of dentin. Distal roots of mandibular third molars were embedded in auto-polymerizing acrylic resin, sectioned coronally to apically resulting in fifty-four root sections. Thirty sections underwent microhardness evaluation, and twenty-four sections were randomly chosen for mineral analysis. The microhardness assessment comprised three groups: Group 1 (2.5% NaOCl), Group 2 (2.5% NaOCl with 0.084% BAC), and Group 3 (2.5% NaOCl with 0.084 BAC post-17% EDTA). Initial and post-irrigation microhardness values were measured for each group. For mineral analysis, samples were categorized into four groups: distilled water, 2.5% NaOCl, 2.5% NaOCl with 0.084% BAC, and 17% EDTA+2.5% NaOCl with 0.084% BAC. X-ray photoelectron spectroscopy immediately measured magnesium, phosphorus, and calcium mineral contents on dentin surfaces post-irrigation. Results indicated a significant reduction in root dentin microhardness for all solutions (p&lt;0.05). However, no statistically significant difference in the percentage of reduction was observed among the groups (p&gt;0.05). XPS analysis revealed no significant disparity in dentin surface mineral content among the groups (p&gt;0.05). In conclusion, the addition of Benzalkonium chloride to sodium hypochloride, either alone or after EDTA, did not induce a significant alteration in dentin microhardness or mineral content. These findings contribute to a nuanced understanding of dental irrigation protocols and their effects on dentin properties during endodontic procedures.

Precipitation kinetics of γ′ and γ′′ particles in Inconel 718 and its influence on mechanical properties

The as-received state of Inconel 718 showcases a γ austenitic structure containing δ intergranular precipitates and a blend of (Nb,Ti)C type carbides. Furthermore, examination via transmission electron microscopy identified γ′′ precipitates (elongated disks) and γ′ precipitates (spherical in shape), with γ′′ being the prevailing phase. After quenching at 990 °C for 30 min, the structure comprises an fcc γ matrix hosting randomly dispersed (Nb,Ti)C carbides. Additionally, the TEM examination of the quenched state showed an absence of the δ phase and γ′′ and γ′ precipitates. The precipitation of γ′′ and γ′ phases was studied in Inconel 718 alloy using specimens which were subjected to isothermal aging for various durations at temperatures between 600 and 750 °C and were previously quenched in water at 990 °C for 30 min. The tensile and the micro-hardness mechanical properties were studied for aging at 680 and 750 °C at 4, 50 and 100 h aging duration. The grain growth kinetic of γ′′ and γ′ precipitates has been analyzed following the power–law relationship Dn= Kt and the rate constant K = K0exp−QRT. The optimum grain growth exponent n of γ′′ and γ′ phases has been determined as equal to 2.3. The activation energy values for γ′′ and γ′ coarsening have been determined as equal to 209 kJ mol−1 and 139 kJ mol−1, respectively. Based on the experimental results, a mathematical model was established to describe the grain growth behavior of the studied Inconel 718 alloy for different tempering temperatures and holding times. The predicted grain size growth is in good agreement with the measured one. For aging at 680 °C, the optimum aging time which corresponds to the highest value of yield strength (1164 MPa) and Vickers micro-hardness (500) due to γ′′ strengthening phase, was determined as 50 h. Nonetheless, when subjected to aging durations surpassing 50 h at 750 °C, the reduction in both yield strength and micro-hardness can be attributed primarily to the coarsening of γ′′ precipitates, followed by a decrease in the volume fraction of the γ′′ phase. This reduction is a result of the concurrent increase in the volume fraction of the δ phase. For γ′′ particle size lower or equal to 35 nm, strengthening is governed by the shearing mechanism. Beyond 35 nm γ′′ particle size, the γ′′ precipitates are crossed preferably by bypassing mechanism. A relationship between the 0.2% yield strength and the Vickers micro-hardness was determined.

Effect of a Nano-hydroxyapatite Toothpaste on Enamel Erosive Lesions of Third Molars Induced by Exposure to Orange Juice.

This study aimed to assess the effect of a nano-hydroxyapatite (nano-HA) toothpaste on erosive enamel lesions of third molars induced by exposure to orange juice. In this in vitro, experimental study, the microhardness of 24 sound-extracted third molars was measured by a Vickers tester. The teeth were then randomly assigned to three groups (n = 8) of nano-HA toothpaste (Pharmed), 1.23% sodium fluoride gel, and artificial saliva. The teeth were exposed to orange juice for 5 min daily for 7 days and were then exposed to nano-HA toothpaste, fluoride gel, or artificial saliva (depending on their group allocation) for 10 min a day. The microhardness of the teeth was measured again after 7 days. Data were analyzed using paired t-test, analysis of variance, and Bonferroni test (alpha = 0.05). Within-group comparisons showed a significant reduction in microhardness of the teeth after the intervention in artificial saliva (P = 0.000), and fluoride gel (P = 0.002) groups. However, no significant reduction occurred in the microhardness of the nano-HA group, compared with the baseline (P = 0.132). Between-group comparisons revealed no significant difference in the microhardness of the three groups at baseline (P > 0.05). However, after the intervention, the microhardness of the nano-HA group was significantly higher than that of other groups (P < 0.05). However, the difference in secondary microhardness between fluoride gel and artificial saliva groups was not significant (P = 1.00). Pharmed toothpaste containing nano-HA has optimal efficacy for remineralization of enamel erosive lesions induced by exposure to orange juice.

Physicochemical properties of flowable composites using isobornyl methacrylate as diluent monomer.

this study sought to evaluate the effect of isobornyl methacrylate (IBOMA) as a diluent monomer on the physicochemical properties of experimental flowable resin composites. the organic resin matrix of a modal flowable resin composite was formulated with 50 wt.% of bisphenol-A-glycidyl methacrylate (Bis-GMA) and 50 wt.% of a diluent monomer, in which IBOMA was used as a combining or substituent diluent monomer to triethylene glycol dimethacrylate (TEGDMA). The resin matrices were filled with 55 wt.% particles, of which 10 wt.% was 0.05-μm fumed silica, and 45 wt.% was 0.7-μm BaBSiO2 glass. Polymerization shrinkage stress (PSS; n=10), degree of conversion (DC; n=3), maximum rate of polymerization (Rpmax; n=3), film thickness (FT; n=10), sorption (Wsp; n=10), solubility (Wsl; n=10), flexural strength (FS; n=10), flexural modulus (FM; n=10), Knoop microhardness (KH; n=10), and microhardness reduction after chemical softening (HR; n=10) were evaluated. Data were analyzed using one-way ANOVA, followed by Tukey's test (α=0.05; β=0.2). the results showed that the substitution or addition of IBOMA reduced FT (p=0.001), PSS (p=0.013), Rpmax (p=0.001), DC (p=0.001), FM (p=0.006) Wsp (p=0.032), and Wsl (p=0.021). However, when used as a complete substituent, IBOMA demonstrated significantly lower FS (p=0.017) and KH (p=0.008), while TEGDMA demonstrated significantly lower HR (p=0.022). the flowable composite containing IBOMA combined with TEGDMA showed no effect in KH and FS and effectively reduced the PSS, RP, FT, Wsp, and Wsl. However, it showed a reduction in DC, FS, and an increase in HR.