Development of cooking method for senior-friendly food using fruits suitable for older adults with masticatory dysfunction.

BACKGROUND/OBJECTIVES: The purpose of this study was to establish a fruit-cooking method suitable for older adults with masticatory dysfunction. MATERIALS/METHODS: Five types of fruits were selected to make fruit jelly and puree: apple, sweet persimmon, mandarin, Korean melon, and watermelon. Recipes were selected based on the Korean Industrial Standard (KS) for senior-friendly foods (KS H 4897), which classifies foods into 3 levels (L1-L3) based on their hardness and viscosity. RESULTS: In South Korea, senior-friendly foods are classified into 3 stages based on their hardness. Stage 1 is for foods that are able to eat with teeth (hardness greater than 50,000 N and less than 500,000 N), Stage 2 is for foods that are able to eat with gums (hardness greater than 20,000 N and less than 50,000 N), and Stage 3 is for foods that are able to eat with the tongue (hardness less than 20,000 N). As a result of measuring the hardness by varying the shape of the fruit, it was found that nearly all fruits could be eaten fresh by chewing with the teeth (L1) but did not meet the KS for mastication using the gums (L2) or tongue (L3), so the cooking method was selected as fruit jelly and fruit puree. Only sweet persimmon, which had a hardness of 61,624-496,393 N, was not suitable for consumption in fresh fruit, unprocessed form. Based on their hardness measurements, fruit jellies (27,869 to 36,343 N) and fruit purees (315 to 1,156 N) met the L2 and L3 requirements, respectively. The viscosity results of all fruit purees met the L3 requirement. CONCLUSION: These results offer a simple cooking method to prepare texture-modified fruits suitable for safe consumption by older adults living with masticatory difficulties in general households and nursing facilities.

Reliability and Validity of Shore Hardness in Plantar Soft Tissue Biomechanics.

Shore hardness (SH) is a cost-effective and easy-to-use method to assess soft tissue biomechanics. Its use for the plantar soft tissue could enhance the clinical management of conditions such as diabetic foot complications, but its validity and reliability remain unclear. Twenty healthy adults were recruited for this study. Validity and reliability were assessed across six different plantar sites. The validity was assessed against shear wave (SW) elastography (the gold standard). SH was measured by two examiners to assess inter-rater reliability. Testing was repeated following a test/retest study design to assess intra-rater reliability. SH was significantly correlated with SW speed measured in the skin or in the microchamber layer of the first metatarsal head (MetHead), third MetHead and rearfoot. Intraclass correlation coefficients and Bland-Altman plots of limits of agreement indicated satisfactory levels of reliability for these sites. No significant correlation between SH and SW elastography was found for the hallux, 5th MetHead or midfoot. Reliability for these sites was also compromised. SH is a valid and reliable measurement for plantar soft tissue biomechanics in the first MetHead, the third MetHead and the rearfoot. Our results do not support the use of SH for the hallux, 5th MetHead or midfoot.

Comparison between a bulk-fill resin-based composite and three luting materials on the cementation of fiberglass-reinforced posts.

Objectives: This study verified the possibility of cementing fiberglass-reinforced posts using a flowable bulk-fill composite (BF), comparing its push-out bond strength and microhardness with these properties of 3 luting materials. Materials and Methods: Sixty endodontically treated bovine roots were used. Posts were cemented using conventional dual-cured cement (CC); self-adhesive cement (SA); dual-cured composite (RC); and BF. Push-out bond strength (n = 10) and microhardness (n = 5) tests were performed after 1 week and 4 months of storage. Two-way repeated measures analysis of variance (ANOVA), 1-way ANOVA, t-test, and Tukey post-hoc tests were applied for the push-out bond strength and microhardness results; and Pearson correlation test was applied to verify the correlation between push-out bond strength and microhardness results (α = 0.05). Results: BF presented higher push-out bond strength than CC and SA in the cervical third before aging (p < 0.01). No differences were found between push-out bond strength before and after aging for all the luting materials (p = 0.84). Regarding hardness, only SA presented higher values measured before than after aging (p < 0.01). RC and BF did not present 80% of the maximum hardness at the apical regions. A strong positive correlation was found between the luting materials' push-out bond strength and microhardness (p < 0.01, R2 = 0.7912). Conclusions: The BF presented comparable or higher push-out bond strength and microhardness than the luting materials, which indicates that it could be used for cementing resin posts in situations where adequate light curing is possible.

Hardness and Depth of Cure of Conventional and Bulk-Fill Composite Resins in Class II Restorations with Transparent and Metal Matrix Strips.

Objectives: Hardness is relevant to the degree of conversion (DC) and depth of cure (DoC). The aim of this study was to determine the micro-hardness and DoC of conventional and bulk-fill composite resins in class II restorations using metal and clear matrix bands. Materials and Methods: Twelve specimens of each of the two composite resins, i.e., Filtek Z350 XT bulk-fill and Gradia posterior conventional composite, were prepared in the form of a class II cavity in a tooth mold, using a clear or metal matrix band. All specimens were cured and stored at 37°C for 24 hours. Vickers hardness was measured as a function of DoC at 2mm intervals. Data were analyzed by two-way ANOVA (alpha=0.05). Results: The bulk-fill composite exhibited significantly higher hardness levels than the conventional composite in all tested surfaces (P<0.001). However, while the metal matrix band had a significant impact on the bottom surface (P=0.059) and also on the furthest surface from the matrix and light source (P=0.04), it did not have a consistent effect across all tested surfaces. The simultaneous interaction of the composites and matrix band types in all surfaces, did not show significant differences in hardness values. The highest bottom-to-top surface hardness ratio (73%) was observed in the conventional composite near the metal matrix band. Conclusion: In deep class II cavities, the bottom-to-top surface hardness ratio did not reach the maximum of 80%, neither for bulk-fill nor conventional posterior composites. Therefore, in such cavities extended light-curing and more incremental composite placement is needed.

Effect of monomer composition and filler fraction on surface microhardness and depth of cure of experimental resin composites.

This study evaluated microhardness profiles and calculated depths of cure at 80% of the surface microhardness of experimental dental resin composites having different base monomer compositions and different filler fractions. Composites were prepared using four different base monomers (bisphenol A-glycidyl methacrylate [Bis-GMA], urethane dimethacrylate [UDMA], ethoxylated bisphenol-A dimethacrylate [Bis-EMA], and Fit-852) with triethylene glycol dimethacrylate (TEGDMA) used as a co-monomer at three filler:resin matrix weight percent fractions (50:50, 60:40, and 70:30). Uncured material was placed in 3D printed molds and light cured for 40 s from the top surface only. Knoop microhardness was measured at the top of the specimen, and at every 0.5 mm up to 4 mm in depth. Microhardness at the surface increased in all experimental composites as the filler fraction increased. When comparing base monomers, microhardness was the highest in UDMA-based composites, while Bis-GMA-based composites showed the lowest values. When comparing depth of cure as a function of base monomer type, both Bis-GMA and Bis-EMA showed significantly lower values than UDMA or Fit-852. Composites having 50 wt% filler showed a significantly higher depth of cure than those with 60 and 70 wt% filler. Base monomer and filler fraction significantly influence microhardness and depth of cure in these experimental composites.

Flexural strength and Vickers hardness of milled and 3D-printed resins for provisional dental restorations

Various forms of temporary resins are offered on the market; however, the properties of temporary resins obtained by milling and 3D printing have not been fully examined. This study aimed to compare the flexural strength and Vickers hardness of milled and 3D-printed resins. Methods: Three resins were tested: Evolux PMMA (milled resin), Cosmos Temp (3D-printed resin), and Structur 2 SC (bis-acrylic resin, group control). Specimens were prepared with rectangular shapes (n = 12) for flexural strength measurements and disc shapes (n = 9) for Vickers hardness tests. Flexural strength tests were performed at a crosshead speed of 0.75 mm/min, and the Vickers hardness was measured under a load of 20 N for 10 s. The obtained data were subjected to the Kruskal­Wallis test. Results: A significant difference (p < 0.05) in flexural strength was observed among the three sample groups: Evolux PMMA (111.76 MPa), Structur 2 SC (87.34 MPa), and Cosmos Temp (56.83 MPa). No significant difference (p < 0.05) was observed between the Vickers hardness values of Structur 2 SC (33.37 VHN) and Evolux PMMA (29.11 VHN); however, both materials were statistically superior to Cosmos Temp (10.90 VHN). Conclusion: While the mechanical properties of the milled resin were superior or similar to those of the bisacrylic resin, the 3D-printed resin was statistically inferior to both the milled and bis-acrylic resins

Evaluation of the Efficacy of CPP-ACP Remineralizing Mousse in MIH White and Yellow Opacities-In Vitro Vickers Microhardness Analysis.

Remineralization of tooth enamel can be partially achieved by the application of a casein phosphopeptides and amorphous phosphate (CPP-ACP) complex. However, evidence to support its effectiveness in Molar-incisor-hypomineralization (MIH)-affected teeth is scarce. The study's aim is to evaluate the efficacy of CPP-ACP mousse in remineralizing MIH-affected enamel using a Vickers microhardness test. Two groups of enamel opacities of hypomineralized permanent teeth, white (group A) and yellow (group B) lesions (n = 14), went through a 28-day treatment protocol with GC Tooth Mousse. Before and after treatment, microhardness was measured in three different areas of each tooth (hypomineralized, transition, and outside the hypomineralized area). Data were analyzed using parametric and non-parametric tests with a significance of p < 0.05. The mean microhardness values increased in the hypomineralized and transition areas in both groups after the treatment protocol (in group A, 105.38 ± 11.70 to 158.26 ± 37.34; 123.04 ± 22.84 to 156.33 ± 35.70; in group B, 108.63 ± 14.66 to 143.06 ± 22.81; 132.55 ± 20.66 to 146.00 ± 12.88) and the differences pre/post-treatment were statistically significant within each group (p < 0.001 for both groups). Between groups, there was a statistically significant difference in the same areas (hypomineralized: p = 0.003; transition: p = 0.008) with a higher improvement in enamel hardness in group A. Topical application of CPP-ACP showed an increase in the physical strength of the hypomineralized and transition areas of MIH-affected enamel, likely due to an increase in mineral content.

Effects of Different Over - the - Counter Whitening Products on the Microhardness, Surface Roughness, Color and Shear Bond Strength of Enamel.

Objective: The purpose of this in vitro study was to evaluate the effects of four over-the-counter (OTC) whitening products on the microhardness, surface roughness, color, shear bond strength (SBS) and surface charecteristics of human enamel compared with a product used for dentist-supervised home whitening. Materials and methods: Seventy eight enamel specimens allocated into 6 groups (n=13): 1-Opalescence PF 10% (OP) dentist prescribed home whitening product, 2-Opalescence Go prefilled tray (PT), 3-Opalescence Whitening Toothpaste (WT), 4-Listerine Healthy White whitening mouth rinse (WMR), 5-Cavex Bite&White whitening pen (WP) and 6- no treatment (Con). The microhardness (VHN), surface roughness (Ra) and color of the specimens were measured (T0). The specimens were then subjected to whitening protocols for 14 days (T1.) followed by artificial saliva storage for 14 days (T2). The measurements were repeated at T1 and T2. The SBS test was done after the application of 35% phosphoric acid (Scotchbond Universal Etchant), followed by a universal adhesive (G-Premio Bond) and a micro hybrid/universal resin composite (Essentia) into a Teflon tube attached to the enamel surface (p<0.05). Surface morphologies of the enamel surfaces were examined by SEM. p value was set at 0.05. Results: Application of OP, PT and WP decrased the microhardness of enamel specimens (p<0.05) whereas, no significant changes were seen in the microhardness of enamel specimens treated with WT and WMR (p>0.05). Ra values of enamel specimens increased with the application of OP, PT and WT (p<0.05); whereas no changes were observed after the applications of WMR and WP (p>0.05). OP, PT, WMR, and WP changed the color of the enamel(p<0.05). There were not any significant differences among the SBSs groups, apart from OP applied enamel specimens. OP showed the least SBS values (p=0.001). SEM observations revealed smooth enamel surfaces. Conclusions: The whitening products affected the microhardness, surface roughness, color of enamel differently. Only OP decreased the SBS of the enamel.

Type I Diabetes Mellitus and Insulin Therapy on Bone Microarchitecture, Composition and Mechanical Properties.

BACKGROUND: The aim of this study was to evaluate the microarchitecture, composition and mechanical properties of cortical bone of rats with type I diabetes mellitus (TIDM) and submitted to insulin therapy (IT). METHODS: Thirty rats were divided into three groups (n=10): non-diabetic, diabetic and diabetic+insulin. TIDM was induced by intravenous injection of streptozotocin. In diabetic+insulin group, 4IU insulin was administered twice per day (1I U at 7 am and 3I U at 7 pm). The animals were euthanized five weeks after TIDM induction; the tibiae were removed and submitted to microcomputed tomography (micro-CT, 8 µm), fourier transform infrared spectroscopy (FTIR) and dynamic microhardness indentation. RESULTS: Micro-CT analysis showed that diabetic group had lower bone surface/tissue volume ratio (BS/BV) (p=0.018), cortical thickness (Ct.Th) (p<0.001) and degree of anisotropy (Ct.DA) (p=0.034) values compared to non-diabetic group. The diabetic group showed lower Ct.Th than diabetic + insulin group (p=0.018). The non-diabetic group had lower fractal dimension (Ct.FD) values compared to diabetic groups (p<0.001). The ATR-FTIR analyses showed lower values for all measured parameters in the diabetic group than the non-diabetic group (amide I ratio: p=0.046; crystallinity index: p=0.038; matrix:mineral ratios - M:MI: p=0.006; M:MIII: p=0.028). The diabetic+ insulin group showed a lower crystallinity index (p=0.022) and M:MI ratio (p=0.002) than nondiabetic and diabetic groups, respectively. The diabetic group showed lower Vickers hardness values than non-diabetic (p<0.001) and diabetic+insulin (p=0.003) groups. CONCLUSION: TIDM negatively affects bone microarchitecture, collagen maturation, mineralization and bone microhardness. Moreover, insulin minimized the effect of TIDM on cortical thickness and organic/mineral matrix.

Influence of fluoride-releasing materials in the inhibition of enamel and dentin demineralization around restorations / Influência de materiais liberadores de flúor na inibição da desmineralização do esmalte e da dentina ao redor de restaurações

Objective: The aim was to evaluate the influence of fluoride-releasing restorative materials in enamel and dentin microhardness. Material and Methods: 40 blocks (5x5x3 mm) from cervical third of human molars received a cavity preparation between the enamel and dentin, and the restorations were subjected to in vitro caries model. Specimens were randomly restored with (n=10): conventional glass ionomer cement (Ketac Cem, 3M ESPE); polyacid-modified composite resin (Ionoseal, VOCO); resin-modified glass ionomer cement (Ionofast, Biodinâmica); or microhybrid composite resin (Filtek Z250, 3M ESPE). The specimens were sectioned longitudinally and enamel and dentin Knoop microhardness were determined at different distances from the restorative material (100, 200 and 300 µm) and depth of surface (20, 40 and 60 µm). The data were submitted to three-way repeated measures ANOVA and Tukey ́s test ( α =0.05). Results: For enamel, the double interactions between material x distance and material x depth were statistically significant. In all depths and distances, the highest values of enamel microhardness were observed for Ketac Cem. In dentin, the materials differed statistically from each other, and Ionoseal obtained higher microhardness values than those found in Ionofast. Conclusion: Conventional glass ionomer cement is more effective in preventing enamel demineralization around restoration followed by the polyacid-modified composite resin. In dentin, the polyacid-modified composite resin obtained better performance than resin-modified glass ionomer cement. (AU)

Objetivo: O objetivo foi avaliar a influência de materiais restauradores liberadores de flúor na microdureza do esmalte e da dentina. Material e Métodos: 40 blocos (5x5x3 mm) do terço cervical de molares humanos receberam preparo cavitário entre esmalte e dentina, e após a restauração foram submetidas a um modelo in vitro de cárie. As amostras foram restauradas aleatoriamente com (n=10): cimento de ionômero de vidro convencional (Ketac Cem, 3M ESPE); resina composta modificada por poliácidos (Ionoseal, VOCO); cimento de ionômero de vidro modificado por resina (Ionofast, Biodinâmica); ou resina composta microhíbrida (Filtek Z250, 3M ESPE). As amostras foram seccionadas longitudinalmente e a microdureza Knoop de esmalte e dentina foi determinada em diferentes distâncias do material restaurador (100, 200 e 300 µm) e profundidade de superfície (20, 40 e 60 µm). Os dados foram submetidos à ANOVA para medidas repetidas de três fatores e teste de Tukey (α =0,05). Resultados: Para o esmalte, as duplas interações entre material x distância e material x profundidade foram estatisticamente significativas. Em todas as profundidades e distâncias, os maiores valores de microdureza do esmalte foram observados para o Ketac Cem. Na dentina, Ionoseal obteve valores de microdureza superiores aos encontrados no Ionofast. Conclusão:O cimento de ionômero de vidro convencional é mais eficaz na prevenção da desmineralização do esmalte ao redor da restauração, seguido pela resina composta modificada por poliácidos. Na dentina, a resina composta modificada por poliácidos obteve melhor desempenho que o cimento de ionômero de vidro modificado por resina. (AU)

Influence of calcium lactate and sodium fluoride solution mouthwashes on enamel microhardness and dentin permeability during in-office bleaching / Influência das soluções enxaguatórias de lactato de cálcio e fluoreto de sódio na microdureza do esmalte e permeabilidade dentinária durante o clareamento em consultório

Objective: This study evaluated the influence of calcium lactate and sodium fluoride mouthwashes on enamel microhardness and dentin permeability during in-office bleaching. Material and Methods: For the microhardness evaluation, enamel blocks were randomly submitted to different treatments associated with in-office bleaching agent using 40% hydrogen peroxide (Opalescence Boost PF 40%/ Ultradent; 3 sessions x 40-minute each) (n = 10): 1) Control: application of bleaching agent; 2) Calcium lactate: 1-minute immersion before bleaching treatment; 3) Sodium fluoride: immersion for 1 minute before bleaching treatment; 4) Calcium lactate + sodium fluoride: 1 minute immersion in calcium lactate solution, followed by 1 minute immersion in sodium fluoride before bleaching treatment. Dentin discs received the same treatment protocols (n = 10) to evaluate permeability. Knoop microhardness and dentin permeability assessments were performed twice (at baseline and 48 hours after the end of bleaching treatment). Results: The generalized linear model considering the design of repeated measures over time showed that there was no significant difference between treatments (p = 0.9577) and between assessments (p = 0.3267) regarding Knoop microhardness. Kruskal Wallis and Dunn tests showed that calcium lactate immersion before bleaching treatment provided higher dentin permeability than other groups (p = 0.0009). Conclusion: The use of sodium fluoride solution and calcium lactate in association with in-office bleaching treatment did not influence the microhardness of tooth enamel, although calcium lactate may increase dentin permeability. (AU)

Objetivo: Este estudo avaliou a influência dos enxaguatórios bucais com lactato de cálcio e fluoreto de sódio na microdureza do esmalte e na permeabilidade da dentina durante o clareamento em consultório. Material e Métodos: Para avaliação da microdureza, blocos de esmalte foram submetidos aleatoriamente a diferentes tratamentos associados a agente clareador em consultório com peróxido de hidrogênio 40% (Opalescence Boost PF 40% / Ultradent; 3 sessões x 40 minutos cada) (n = 10): 1) Controle: aplicação de agente clareador; 2) Lactato de cálcio: imersão de 1 minuto antes do tratamento clareador; 3) Fluoreto de sódio: imersão por 1 minuto antes do tratamento clareador; 4) Lactato de cálcio + fluoreto de sódio: 1 minuto de imersão em solução de lactato de cálcio, seguido de 1 minuto de imersão em fluoreto de sódio antes do tratamento clareador. Os discos de dentina receberam os mesmos protocolos de tratamento (n = 10) para avaliar a permeabilidade. As avaliações da microdureza Knoop e da permeabilidade dentinária foram realizadas duas vezes (no início do estudo e 48 horas após o término do tratamento clareador). Resultados: O modelo linear generalizado considerando o delineamento de medidas repetidas ao longo do tempo mostrou que não houve diferença significativa entre os tratamentos (p = 0,9577) e entre as avaliações (p = 0,3267) em relação à microdureza Knoop. Os testes de Kruskal Wallis e Dunn mostraram que a imersão de lactato de cálcio antes do tratamento clareador proporcionou maior permeabilidade dentinária do que os outros grupos (p = 0,0009). Conclusão: O uso de fluoreto de sódio e lactato de cálcio associado ao clareamento em consultório não influenciou a microdureza do esmalte dentário, embora o lactato de cálcio possa aumentar a permeabilidade dentinária (AU)

O método de fotopolimerização é capaz de influenciar nos valores de microdureza das resinas compostas? Um estudo in vitro / Is the photopolimerization method able to influence on the microhardness values of composite resins? An in vitro study

Introdução: a inovação dos métodos de fotopolimerização foi proposta na tentativa de diminuir o estresse de contração de polimerização das resinas compostas e proporcionar maior conforto ao paciente, reduzindo o tempo de atendimento odontológico. Objetivo: avaliar a microdureza de duas resinas compostas nanoparticuladas submetidas a diferentes técnicas de polimerização. Material e método: quarenta espécimes foram divididos em quatro grupos (n=10) da seguinte forma: Filtek Z350 XT® + técnica imediata (GI); Filtek One Bulkfill® + técnica imediata (GII); Filtek Z350 XT® + técnica de pulso tardio (GIII); Filtek One Bulkfill® + técnica de pulso tardio (GIV). Após o armazenamento em água destilada à temperatura ambiente, os corpos de prova foram direcionados para a medição de microdureza. Utilizou-se teste T para comparação de técnicas e teste Two-Way ANOVA para calcular os efeitos das resinas compostas, técnicas de polimerização e interações referentes à variável dependente (p ≤0,05). Resultado: a resina Filtek Z350 XT® apresentou maior dureza na técnica imediata (GI - 312,45 ± 64,37) e pulso tardio (GIII - 244,50 ± 75,63) comparado à resina Filtek One Bulkfill®, em ambas as técnicas. Observaram-se maiores valores de dureza referentes à técnica imediata, com diferença estatística significativa em relação à resina testada (p = 0,04 - Filtek Z350 XT®; p = 0,03 - Filtek One Bulkfill®). Ambos os fatores isolados (resina e técnicas) apresentaram efeito nos valores de microdureza (p = 0,02 e p < 0,01, respectivamente). Conclusão: a técnica convencional demonstrou atingir maiores valores de dureza quando comparada à técnica de polimerização alternativa.

Introduction: the innovation of photopolymerization methods was proposed in an attempt to reduce the polymerization shrinkage stress of composite resins and also provide more comfort to patient reducing the chair time. The aim of this in vitro study was to assess the microhardness of two nanofilled composite resins subject to different curing techniques. Objective: assess the microhardness of two nanofilled composite resins subject to different curing techniques. Material and method: forty specimens were divided into four groups (N=10) as follows: Filtek Z350 XT® + immediate technique (GI); Filtek One Bulkfill® + immediate technique (GII); Filtek Z350 XT® + delayed pulse technique (GIII); Filtek One Bulkfill® + delayed pulse technique (GIV). After storage in distilled water at room temperature the specimens were assessed for microhardness measurement. T-test was used for comparison of techniques and two-way ANOVA used to calculate the effects of composite resins, curing techniques and their interactions on dependent variable (p set at 0.05). Result: Filtek Z350 XT® resin presented greater hardness on immediate technique (GI - 312,45 ± 64.37) and delayed pulse (GIII - 244,50 ± 75.63) compared to Filtek One Bulkfill® under both techniques. Overall, it was observed greater hardness values under immediate technique with a significant statistical difference apart of tested resin (p = 0.04 - Filtek Z350 XT®; p = 0.03 - Filtek One Bulkfill®). Both isolated factors (resin and techniques) presented effect on microhardness values (p = 0.02 and p < 0.01, respectively). Conclusion: the conventional technique demonstrated to reach higher hardness values when compared to the alternative polymerization technique

The Influence of Rapid Solidification on Corrosion Behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 Alloy for Medical Applications.

Biodegradable magnesium alloys with Zn, Yb, Ca and Sr additions are potential materials with increased corrosion resistance in physiological fluids that ensure a controlled resorption process in the human body. This article presents the influence of the use of a high cooling rate on the corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy proposed for medical applications. The microstructure of the alloy in a form of high-pressure die-casted plates was presented using scanning electron microscopy in the backscattered electrons (BSEs) mode with energy-dispersive X-ray spectrometer (EDX) qualitative analysis of chemical composition. The crystallization mechanism and thermal properties were described on the basis of differential scanning calorimetry (DSC) results. The corrosion behavior of Mg60Zn20Yb15.7Ca2.6Sr1.7 alloy was analyzed by electrochemical studies with open circuit potential (EOCP) measurements and polarization tests. Moreover, light microscopy and X-ray photoelectron spectroscopy were used to characterize the corrosion products formed on the surface of studied samples. On the basis of the results, the influence of the cooling rate on the improvement in the corrosion resistance was proved. The presented studies are novel and important from the point of view of the impact of the technology of biodegradable materials on corrosion products that come into direct contact with the tissue environment.

Evaluation of the Effect of Long-term Use of Three Intracanal Medicaments on the Radicular Dentin Microhardness and Fracture Resistance: An in vitro study.

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.

Influence of Using Different Light Curing Devices on the Microhardness of a Bulk-Fill Resin / Influência da Utilização de Diferentes Aparelhos Fotopolimerizadores na Microdureza de uma Resina Bulk Fill

Bulk Fill resins are a class of resin composites widely used today and have low polymerization shrinkage. However, these materials need an appropriate light curing technique to have good physical and mechanical properties. The objective of this study was to evaluate the surface microhardness of Bulk Fill resins after their light-curing with two types of high- power light curing devices, using three techniques. 30 specimens were made with a nanoparticulate composite resin Opus Bulk Fill (FGM) and were divided into three groups according to the device and intensity of light curing: Group 1 - light curing with the Emitter B device (Schuster); Group 2 - light curing with the Valo device (Ultradent) at Standard power; and Group 3 - light curing with the Valo device at high power. Higher values of top surface microhardness were observed in Group 3 (microhardness = 53.6 µm), followed by Group 2 (microhardness = 52.1 µm) and Group 1 (microhardness = 33.1 µm), with p values <0.05. Therefore, the Valo light curing unit, in the two powers used, provided greater surface microhardness for the studied specimens. (AU)

Resinas Bulk Fill são uma classe de compósitos resinosos bastante utilizados atualmente e apresentam baixa contração de polimerização. Entretanto, esses materiais necessitam de uma adequada técnica de fotopolimerização para que apresentem boas propriedades físicas e mecânicas. O objetivo deste estudo foi avaliar a microdureza superficial de resinas Bulk Fill fotopolimerizadas com dois tipos de aparelhos fotopolimerizadores de alta potência, em três técnicas de utilização. Foram confeccionados 30 corpos de prova com uma resina composta nanoparticulada Opus Bulk Fill (FGM) e divididos em três grupos de acordo com o aparelho e intensidade de fotopolimerização: Grupo 1 ­ fotopolimerização com o aparelho Emitter B. (Schuster), Grupo 2 ­ fotopolimerização com o aparelho Valo (Ultradent) na potência Standard, Grupo 3 ­ fotopolimerização com o aparelho Valo em alta potência, posteriormente foi realizado o teste de microdureza de Vickers na região superficial de topo dos corpos de prova. Observou-se maiores valores de microdureza superficial de topo no Grupo 3 (microdureza= 53,6 µm), seguido pelo Grupo 2 (microdureza= 52,1 µm) e Grupo 1 (microdureza= 33,1 µm), com valores de p<0,05. Assim sendo, o aparelho fotopolimerizador Valo, nas duas potências utilizadas, forneceu maior microdureza superficial para os corpos de prova estudados. (AU)

Long-term effect of acidic pH on the surface microhardness of ProRoot mineral trioxide aggregate, Biodentine, and total fill root repair material putty.

BACKGROUND: The purpose of this study was to compare the microhardness values of ProRoot mineral trioxide aggregate (MTA), Biodentine, and total fill root repair material (TF-RRM) Putty at varying pH and times. MATERIALS AND METHODS: In this laboratory experiment, materials were mixed and placed in cylinder blocks with internal dimensions of 6 mm × 4 mm. Ten samples of each material were soaked in buffered solutions of butyric acid with 4.4, 5.4, 6.4, and 7.4 pH values and stored at 37°C in 100% humidity. The samples were submitted to the microhardness test at the end of 1 week and then 1 month. Multivariate analysis of variance and Tukey honestly significant difference tests were carried out to compare the mean values at a significance level of P < 0.05. RESULTS: Low pH caused a significant decrease in the microhardness values of all samples. Surface microhardness increased with time (P < 0.0001). The microhardness values of Biodentine were significantly greater than those of ProRoot MTA and TF-RRM putty (P < 0.0001). The lowest microhardness values were recorded for TF-RRM putty groups regardless of the pH of the environment and the evaluation time. CONCLUSION: An acidic environment impaired the surface microhardness of all root repair materials tested. Overall, the mean surface microhardness of TF-RRM Putty was lower than those of ProRoot MTA and Biodentine. Biodentine showed the greatest microhardness values at all pH values, regardless of the evaluation time.

Effect of fluoride varnish on glass ionomer microhardness changes in endogenous acid erosion challenge.

OBJECTIVE: This study aimed to assess the effect of fluoride varnish on glass ionomer microhardness changes after endogenous acid erosion challenge. METHODOLOGY: In this study, 40 conventional glass ionomer (CGI; Fuji IX) and 40 resin-modified glass ionomer (RMGI; Fuji IILC) discs were fabricated and divided into 4 subgroups (n = 10) for immersion in synthetic gastric acid or saliva for 27 h with/without fluoride varnish application. The surface microhardness was measured at baseline and after immersion, and the change in microhardness was calculated. Data were analyzed using analysis of variance and T-test. RESULTS: A reduction in microhardness was noted in all subgroups following immersion. The lowest change in microhardness of both CGI and RMGI occurred in artificial saliva. In CGI groups, the highest reduction in microhardness occurred in synthetic gastric acid with fluoride varnish application, and the reduction was significantly different from that of the CGI group with fluoride varnish application (p value = .01). In RMGI groups, the highest reduction in microhardness was noted in synthetic gastric acid without fluoride varnish application, and the reduction was significantly different from that of the other groups (p value < .05). CONCLUSIONS: Exposure to synthetic gastric acid caused a significant reduction in microhardness of RMGI. Varnish application significantly decreased the acid susceptibility of RMGI, but not that of CGI.

Silver Diamine Fluoride versus Bioactive Giomer Light-Curing Varnish: An In Vitro Study on Caries Arrest

ABSTRACT Objective To compare the capacity of silver diamine fluoride (30%) and the bioactive giomer light-curing varnish for arresting ICDAS score 5 non-retentive caries lesions. Material and Methods An in vitro analytical study was conducted using 36 healthy primary teeth, in which a cavity was created, divided into 3 groups: control (distilled and deionized water), giomer-based light-curing varnish - Barrier Coat, and Silver Diamine Fluoride 30% - Cariestop (SDF). The samples were analyzed for mineral loss as measured by surface microhardness (SMH).The Knoop microhardness test was performed using the HVS-1000 microhardness tester. The data were compared by two-way analysis of variance - treatment and time (before and after treatment) followed by Tukey's post-test. The significance level adopted in all analyzes was 5%. Results The specimens treated with giomer showed higher SMH compared to the untreated group but were similar to those of the SDF group. The SDF group, on the other hand, showed no statistically significant difference from the control group (p=0.010). Conclusion The giomer varnish had a remineralizing effect on artificial dentinal caries.

Effect of irrigation protocols on root canal wall after post preparation: a micro-CT and microhardness study

Abstract: The aim of this study was to investigate the effects of different post space irrigation protocols for removing residual filling material from dentin walls, by using microcomputed tomography (micro-CT), and the influence of these protocols on dentin microhardness. Bovine incisors (n = 35) were filled with the single-cone technique and MTA Fillapex (Angelus, Londrina, PR, Brazil). Post space preparation (PSP) was performed 7 days after filling, using the Odous Touch electrical system (Odous De Deus Ind. e Com., Belo Horizonte, MG, Brazil), followed by post space irrigation using manual irrigation, passive ultrasonic irrigation, or Easy Clean, together with 2.5% sodium hypochlorite (NaOCl), or with 2.5% NaOCl and 17% EDTA (NaOCl/EDTA). Micro-CT scans were performed at three time points. The residual filling material was evaluated at three levels: cervical, middle and apical. The Knoop test was measured with four indentations around the canal lumen at three dentin depths: X (100 μm), Y (200 μm) and Z (400 μm). Statistical analysis was performed using ANOVA (p < 0.05). The effects of the activation method (p < 0.001), and the root level (p = 0.013), as well as the interaction between the irrigant and the activation method (p = 0.041), led to different percentages of residual filling material. Lower amounts of residual filling material were observed at the cervical versus the middle and apical levels (p < 0.05). No significant differences were observed in dentin microhardness (p > 0.05). The best removal of the residual filling material was performed using the Easy Clean tip and NaOCl/EDTA, regardless of the activation methods.

Initial Mechanical Stabilization of Conventional Glass Ionomer Cements with Different Active Principles

ABSTRACT Objective: To determine the initial mechanical stabilization of conventional glass ionomer cements (GICs) indicated for the atraumatic restorative treatment (ART) in different storage periods. Material and Methods: Specimens were divided according to the GIC (n=12): IZ - Ion-Z, KM - Ketac Molar Easymix, RS - Riva Self Cure, and GL - Gold Label 9. They were prepared and stored in distilled water. Superficial microhardness (SMH) was evaluated (KHN) in three phases: (A) after 1, (B) 3, and (C) 7 days of storage. Data were submitted to 2-way ANOVA and Tukey tests (α = 5%). Results: The average KHN values for phases A, B, and C were, respectively, 33.05 ± 9.74; 33.21 ± 10.31 and 52.07 ± 11.75 (IZ); 50.35 ± 11.39; 66.05 ± 10.48 and 67.77 ± 13.80 (KM); 89.63 ± 15.59; 71.31 ± 23.86 and 57.70 ± 16.89 (RS); 42.18 ± 9.03; 68.54 ± 6.83 and 57.95 ± 8.24 (GL). Significant differences were observed: GIC, time, and interaction of both (p<0.05). KHN values differed between the groups, except in the GIC parameter for KM and GL. The time parameter values of phase A were lower than those of B and C, except for IZ and RS. Conclusion: The initial mechanical stabilization differed between the types of GIC tested and the storage time, and after the final period, all had similar SMH.