Cylindrical Mold Research Articles

The Effect of Human Blood and Platelet-rich Fibrin on the Surface Microhardness of Hydraulic Calcium Silicate-based Cements

Objectives: This study aimed to compare the effect of human blood and platelet-rich fibrin (PRF) on the surface microhardness of hydraulic calcium silicate-based cements (OrthoMTA and RetroMTA). Materials and Methods: Two types of mineral trioxide aggregate, OrthoMTA and RetroMTA, were mixed and placed into cylindrical molds. The lower surfaces of all cements were exposed to saline. The upper surfaces of cements were exposed to human blood, PRF, or phosphate buffer saline (PBS). After storage for 7 days in fully saturated humidity at 37°C, the microhardness of cement surface exposed to blood, PRF, or PBS was measured using the Vickers microhardness test. The data were analyzed using two-way analysis of variance and post hoc Tamhane’s T2 test. The significance level was set at P<0.05. Results: Exposure to blood and PRF significantly decreased the surface microhardness of OrthoMTA and RetroMTA. The microhardness of PBS-contacted cements was significantly higher than that of blood or PRF groups (P<0.001). The microhardness values for OrthoMTA exposed to PRF were significantly higher than the blood group (P=0.020). There were no significant differences between RetroMTA contacted with blood or PRF groups (P=0.985). When exposed to blood or PBS, RetroMTA had a significantly higher microhardness than OrthoMTA (P<0.001 for blood, P=0.002 for PBS). Conclusion: Exposure to blood or PRF decreased the surface microhardness of both cements. Blood-contaminated RetroMTA showed significantly higher surface microhardness than OrthoMTA contacted with blood. No significant difference was found between PRF-contacted OrthoMTA and RetroMTA.

Shear Bond Strength of Five Different Repair Systems to Three Different Ceramic Materials.

The purpose of the current study was to investigate the shear bond strength of composite resin in five different ceramic repair systems for three different ceramic materials. 225 monolithic zirconia (Zr) and lithium disilicate (LDS) and cobalt chromium (CoCr) specimens with feldspathic porcelain (FP) veneer were fabricated (N=75 per material). The specimens underwent thermo-cycling and were randomly divided into five groups for the following intra-oral repair systems (n=15): 1) Clearfil Ceramic Primer Plus, Kuraray Noritake, Japan; 2) Ibond Intraoral Repair Kit, Kulzer, Germany; 3) VOCO Cimara, VOCO GmbH Germany; 4) Ivoclar Vivadent, Ceramic Repair System Kit, IvoclarVivadent, Liechtenstein; 5) Ultradent Porcelain Repair Kit, Ultradent Products Inc, USA. After surface conditioning, composite was applied using a cylindrical mold and a second round of thermocycling was performed. Each specimen was then subjected to shear load until failure. Microshear bond strength was compared using analysis of variance (one-way ANOVA, Tukey's test, a <0.05). Type of porcelain repair kit significantly affected the shear bond strength. For Zr, the repair systems from Kulzer and VOCO had significantly higher shear bond strength than the other systems (p<0.001) without significant difference between Kulzer and VOCO. For the LDS and CoCr with FP, hydrofluoric acid had the highest shear bond strength (p<0.001). For zirconia, a 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) system should be used. The results also suggest that a cleaning bur may be beneficial. For glass-based ceramics and feldspathic porcelain, etching with hydrofluoric acid remains the product of choice.

A Comparison of the Shear Bond Strength between a Luting Composite Resin and Both Machinable and Printable Ceramic–Glass Polymer Materials

This study aims to compare the shear bond strength (SBS) and Weibull characteristics between a luting composite resin and both printable and two different machinable ceramic–glass polymer materials. A total of 36 substrates were prepared, with 12 in each group. Printable substrates (12 mm × 12 mm × 2 mm) were printed by using permanent crown resin (3D-PR). Machinable substrates were obtained from Cerasmart 270 (CS) and Vita Enamic (VE) blocks (2 mm in thickness). The bonding surfaces of substrates were polished and airborne abraded (50 µm Al2O3). A self-adhesive luting composite resin (RelyX U200, 3M ESPE, St. Paul, MN, USA, SLC) was applied on substrates with the help of a cylindrical (Ø3 × 3 mm) mold. The SBS test was conducted using a universal test machine. The SBSs of three materials were compared using a one-way analysis of variance (ANOVA) (α = 0.05). The Weibull modulus was calculated for each material. The Kruskal–Wallis and chi-square tests were carried out for the failure mode analysis. There was no significant difference between the SBSs of the three materials (p = 0.129). The Weibull modulus was 3.76 for the 3D-PR, 4.22 for the CS, and 6.52 for the VE group. Statistical analysis showed no significant difference between the failure modes of the groups (p = 0.986). Mixed-failure fractures were predominantly observed in all three groups. The results show that the SBS of the SLC to printable 3D-PR is comparable to that of CS and VE material. Failure modes of printable 3D-PR show similar results with two different machinable ceramic–glass polymers.

Shear Bond Strength of Self-Adhesive Versus Conventional Flowable Composites: An In Vitro Study

Abstract Aim: As an emerging yet underexplored innovation in dentistry, self-adhesive flowable composites (SAFCs) represent a promising and enduring advancement in the dental material technology. Our study aims to evaluate the shear bond strength of two SAFCs and the bonding of conventional flowable composite (CFC) to permanent dentin. Materials and Methods: Thirty-six teeth were embedded in acrylic blocks, with the occlusal third removed to expose the underlying dentin. A cylindrical mold was positioned on the treated dentin surface and filled with the composite resin material to be evaluated. The prepared permanent dentin surfaces were randomly assigned to three groups based on the following application protocols: Group 1: Axo Uni Flow (AXIMACK, India); Group 2: Constic (DMG, Germany); and Group 3: 37% phosphoric acid etchant + Single Bond Universal + Filtek Z350 XT (3M ESPE, USA). The shear bond strength of the prepared specimens was measured by using a universal testing machine. The data were analyzed with Kruskal–Wallis one-way analysis of variance, followed by Dwass–Steel–Critchlow–Fligner pairwise comparisons. Results: Filtek Z350 XT (3M ESPE, USA) demonstrated higher shear bond strength values when compared to Constic (DMG, Germany) and Axo Uni Flow (AXIMACK, India). A significant difference was found between these materials. However, the shear bond strength of the two SAFCs tested did not differ significantly. Conclusion: The investigation’s findings suggest that the SAFCs exhibited inferior shear bond strength compared with CFCs when bonded with permanent dentin.

Experimental Study on the Temperature-Dependent Static, Dynamic, and Post-Dynamic Mechanical Characteristics of Municipal Solid Waste.

Municipal solid waste (MSW) has huge potential to be recycled as construction material, which would have significant benefits for environmental conservation. However, the cornerstone of this undertaking is a solid comprehension of the mechanical response of MSW in real-world engineering locations, taking into account the effects of stress levels and temperature. In this paper, well-mixed MSW samples were sieved and crushed to produce standardized specimens in cylindrical molds. A series of static, dynamic, and post-cyclic shear tests were conducted on the MSW at temperatures ranging from 5 °C to 80 °C with normal stresses of 50 kPa, 100 kPa, and 150 kPa. The experimental findings demonstrate that the static, dynamic, and post-cyclic mechanical response of MSW presents temperature range-dependency; temperature variation between 5 °C and 20 °C affects MSW's mechanical reaction more than variation in temperature between 40 °C and 80 °C under various stress settings; at 5 °C~80 °C, the static peak shear strength of MSW is the highest, being followed by the post-cyclic peak shear strength, while the dynamic peak shear strength is the lowest; the sensitivity of the dynamic shear strength of MSW to temperature variation is the largest, being followed by the post-cyclic peak shear strength, and the static peak shear strength is the lowest.

Correlation between Dental Composite Filler Percentage and Strength, Modulus, Shrinkage Stress, Translucency, Depth of Cure and Radiopacity.

Filler content in dental composites is credited for affecting its physical and mechanical properties. This study evaluated the correlation between the filler percentage and strength, modulus, shrinkage stress, depth of cure, translucency and radiopacity of commercially available high- and low-viscosity dental composites. Filler weight percentage (wt%) was determined through the burned ash technique (800 °C for 15 min). Three-point bend flexural strength and modulus were measured according to ISO 4049 with 2 mm × 2 mm × 25 mm bars. Shrinkage stress was evaluated using a universal testing machine in which composite was polymerized through two transparent acrylic rods 2 mm apart. Shrinkage was measured from the maximum force following 500 s. The translucency parameter (TP) was measured as the difference in color (ΔE00) of 1 mm thick specimens against white and black tiles. The depth of cure was measured according to ISO 4049 in a cylindrical metal mold (4 mm diameter) with a 10 s cure. Radiopacity was measured by taking a digital X-ray (70 kVp for 0.32 s at 400 mm distance) of 1 mm thick specimens and comparing the radiopacity to an aluminum step wedge using image analysis software. The correlation between the filler wt% and properties was measured by Pearson's correlation coefficient using SPSS. There was a positive linear correlation between the filler wt% and modulus (r = 0.78, p < 0.01), flexural strength (r = 0.46, p < 0.01) and radiopacity (r = 0.36, p < 0.01) and negative correlation with translucency (r = -0.29, p < 0.01). Filler wt% best predicts the modulus and strength and, to a lesser extent, the radiopacity and translucency. All but two of the high- and low-viscosity composites from the same manufacturer had statistically equivalent strengths as each other; however, the high-viscosity materials almost always had a statistically higher modulus. For two of the flowable composites measured from the same manufacturer (3M and Dentsply), there was a lower shrinkage stress in the bulk-fill version of the material but not for the other two manufacturers (Ivoclar and Tokuyama). All flowable bulk-fill composites achieved a deeper depth of cure than the flowable composite from the same manufacturer other than Omnichroma Flow Bulk.

Evaluation of Surface Microstructure and Compressive Strength of Mineral Trioxide Aggregate and Biodentine in the Existence and Absence of Oral Tissue Fluids.

Calcium silicate cement like mineral trioxide aggregate (MTA) and Biodentine are known for their biocompatibility and are effectively used as retrograde filling materials. During their placement, the materials interact with oral tissue fluids like saliva and blood, so the aim of the present study was to assess the effect of distilled water, saline, and blood on the surface microstructure and compressive strength of MTA and Biodentine. In this experimental study, a total of 84 custom-made cylindrical molds were randomly allocated into two main cement groups (n = 42) MTA and Biodentine. Each group was further subdivided into three subgroups (n = 14) as per the testing conditions, that is, samples exposed to distilled water, saline, and fresh blood. Around 10 samples from each subgroup were tested for compressive strength using a universal testing machine (UTM), and the remaining four samples were used to examine the surface characteristics of MTA and Biodentine using a scanning electron microscope (SEM). One-way analysis of variance (ANOVA) and Tukey's post hoc tests were employed to calculate the mean compressive strength and standard deviation values. There was a significant difference in the compressive strength between MTA and Biodentine, especially in the presence of blood. During the SEM analysis, it was found that samples contaminated with blood or saline were devoid of acicular crystals in both groups. MTA group showed a more porous matrix with few hexagonal crystals than Biodentine. Biodentine may be advantageous as a root-end filling or root repair material in the presence of blood. Bhullar KK, Gupta V, Sapra M, et al. Evaluation of Surface Microstructure and Compressive Strength of Mineral Trioxide Aggregate and Biodentine in the Existence and Absence of Oral Tissue Fluids. Int J Clin Pediatr Dent 2024;17(S-1):S1-S5.

Preparation and characterization of ZnO modified solid state sintered 45S5 bioactive ceramics

In this research, the traditional 45S5 bioactive glass powder was modified using ZnO (<20 μm) by powder metallurgy route. Five different bioactive ceramics compositions (45BC, 45BC1, 45BC3, 45BC5 and 45BC7) were formulated containing varied amounts of ZnO in the step of 1, 3, 5 and 7 wt % respectively. Each body was thoroughly mixed in a porcelain-lined ball mill to ensure proper homogenization followed by an addition of prepared 2 % PVA (Polyvinyl alcohol) and then again thoroughly mixed. The batch material was uniaxially pressed at 70 MPa using a cylindrical mould of 40 × 20 mm. A total of 20 samples from each body composition were produced and allowed to dry in an ambient temperature followed by sintering at 1000 °C for 2h at the rate of 5 °C/min. The samples were then allowed to anneal within the furnace to room temperature. Selected samples were later immersed inside simulated body fluid. Physical, mechanical, microstructure and phase evaluation were conducted to examine the developed bioactive ceramics. The results showed that the bulk density increased from 1.6 to 2.64 g/cm3 while porosity decrease from 95 % to 58 % across the series, with increasing ZnO addition. Sample 45BC7 showed maximum hardness and compressive strength of 7.98 GPa and 83.54 MPa respectively. The carbonate-hydroxyapatite/hydroxyapatite (CHA/HA) deposits were found to also increased with ZnO addition showing good bioactivity, which affirms that the developed bioactive ceramics can bond well with living tissues, thus its suitability for bone regeneration.

Evaluation of Physical Properties in Carboxymethyl Chitosan Modified Glass Ionomer Cements and the Effect for Dentin Remineralization: SEM/EDX, Compressive Strength, and Ca/P Ratio.

The aim of this article was to evaluate the effects of modifying glass ionomer cement (GIC) with carboxymethyl chitosan (CMC) on surface morphology and remineralization outcomes by examining dentin morphology and calcium ion composition changes. Thirty holes in a cylindrical acrylic mold were filled with three groups of restorative materials: GIC, GIC modified with CMC (GIC-CMC) 5%, and GIC-CMC10%. The surface morphology of each group's materials was observed using scanning electron microscopy (SEM). The compressive strength measurement was performed using a universal testing machine. The dentin remineralization process was performed by applying GIC, GIC-CMC5%, and GIC-CMC10% materials for 14 days on demineralized dentin cavities treated with 17% ethylenediamine tetraacetic acid (EDTA) for 7 days. A morphological evaluation was conducted using SEM. The calcium ion composition and calcium-to-phosphorous (Ca/P) ratio were examined using an energy-dispersive X-ray (EDX). The Kruskal-Wallis and post-hoc Mann-Whitney U tests were performed to compare all four groups of calcium ions (p < 0.05). The modification of GIC with CMC affected the morphological changes in the materials in the form of reduced porosity and increased fractures. A significant difference was found in compressive strength between the GIC-CMC modification materials of GIC-CMC5% and GIC-CMC10% and the GIC control group. The dentin tubule morphology and surface changes were observed after applying GIC, GIC-CMC5%, and GIC-CMC10% materials for 14 days, as evaluated by SEM. The EDX examination showed an increase in calcium ion content and hydroxyapatite formation (Ca/P ratio) after applying the GIC-CMC10% material. The surface porosity of the GIC modification material with the addition of CMC tended to decrease. However, an increase in cracked surfaces that widened, along with the rise in CMC percentage, was found. This modification also reduced the compressive strength of the materials, with the lowest average yield at 10% CMC addition. Therefore, the modification of GIC with CMC affects changes in morphology, calcium ion composition, and Ca/P ratio in demineralized dentin.

Bulk-fill composite in challenging cavities: conversion rate, solubility, and water absorption analysis.

In a deep, curved cavity, polymerization of a bulk fill composite can be challenging. The aim of this study was to investigate the solubility, water absorption, and conversion rate of bulk-fill composite samples prepared using molds with various slope angles. Bulk-fill composite resin (Filtek One Bulk Fill) was placed into cylindrical Teflon molds with a depth of 4mm, angled at varying degrees (90°, 75°, 60°, 45°). Two different LED light-curing units (VALO Cordless, iLed Curing Light) were used to cure the samples. Polymerizations were performed at three different distances (0mm, 2mm, and 4mm). Five samples per group were used, resulting in a total of 24 groups. The Fourier Transform Infrared Spectrometer was utilized to evaluate the conversion levels of the samples. Water sorption and solubility values were determined by storing the composites in distilled water at 37°C for 21days. The VALO light-curing unit applied closest to samples inserted in a 90° angulation mold had the highest mean degree of conversion (41.55%), while iLED light-curing unit group that applied from 4mm to the samples inserted in a 45° angulation mold had the lowest mean conversion (8.97%). The angle of the cavity and the distance at which the light-curing unit is applied significantly affected bulk-fill composite resin conversion. In addition, the choice of light-curing unit impacted the conversion levels. However, with the tested conditions, the water sorption and solubility values of polymerized composite resin samples remain unaffected by these factors.

Comparative Evaluation of the Mechanical and Physical Properties of Mineral Trioxide Aggregate vs. Bacterial Cellulose Nanocrystal-Reinforced Mineral Trioxide Aggregate: An In Vitro Study.

This study aims tocompare and assess the compression strength, microhardness, and surface texture of two sets of materials: mineral trioxide aggregate (MTA) PlusTMand bacterial cellulose nanocrystal (BCNC)-reinforced MTA PlusTM. According to the ASTM E384 standard, the cylindrical molds made of plexiglass with an internal diameter of 6 mm and a height of 4 mm were fabricated using computer numerical control laser cutting. A total of 20 samples (n=10) in each group were considered in this experimental study: Group I (control group) MTA PlusTM (Prevest DenPro Limited, India)and Group II (experimental group) BCNC (Vedayukt India Private Limited, India)-reinforced MTA PlusTM. After preparation, the molds were incubated at 37°C in a fully saturated condition for about 24 hours, and then the compression strength, microhardness, and scanning electron microscopy analyses were performed at different magnifications. The obtained data were then statistically analyzed. Quantitative analysis revealed that there is a statistically significant difference between MTA PlusTM and BCNC-reinforced MTAPlusTM (p<0.002). The Wilcoxon signed-ranktest and Mann-Whitney U-test revealed that BCNC-reinforced MTA PlusTM showed significantly higher compression strength (33.80±3.83 MPa, p=0.00) and surface microhardness (642.85±24.00 μm, p=0.00) than the control group. Based on ourfindings, it was concluded thatthere is a statistically significant difference between both study groups. Thus, incorporating BCNC into the MTA PlusTM significantly increased the compression strength and surface microhardness of the MTA PlusTM cement. Numerous dental applications have been investigated for bacterial cellulose. Many benefits of bacterial cellulose are available, which includeits effects on moldability, low cost, high water retention capacity, biocompatibility, and biodegradability. Furthermore, the addition of BCNC to MTA PlusTM accelerates the material's hardening process and decreases its setting time, which in turn shortens clinical chairside procedural timing and thereby improves patient satisfaction.

Mold material and dimension effects on the microstructural gradient in a glass-ceramic

Microstructural gradients can significantly affect the properties of glass-ceramics (GCs). Such spatial variations in glass-ceramic (GC) microstructure may result from a non-uniform cooling rate when the glass-forming liquid is cast into a mold. This study investigates the material and mold size influence on the cooling process, leading to a non-uniform distribution of crystalline nuclei in the parent glass. We used a high-nucleation rate, non-stoichiometric, lithium metasilicate GC as a model. Initially, the glass-forming liquid was cooled in cylindrical molds with diameters of 7 and 14 mm, made from copper and 304 stainless steel – materials with distinct thermal diffusivities. Simulated thermography, validated by thermocouple data, showed contrasting cooling profiles across the samples. Our key findings are: i) cooling rate: faster cooling in the smaller mold resulted in a lower crystal number density and a reduced crystallized volume fraction (αv) as expected; ii) mold material: surprisingly, copper molds led to quicker glass shrinkage, which facilitated the earlier formation of air gaps with reduced heat transfer and slower cooling than steel, favoring incipient crystallization during the cooling path; iii) microstructure: samples cooled in both molds exhibited higher αv in the central and upper (mold contact-free) regions due to slower cooling compared to the mold base and edges. Therefore, this study reveals how mold material and size affect microstructural gradients in GCs, paving the way for tailoring crystallization and microstructure through strategic mold design.

Color Stability and Surface Roughness of Different Composite Resins after Using Different Polishing Systems.

Background and objectives: To evaluate and compare the color stability and surface roughness of different composite resins after using different polishing systems and then submitting to accelerating artificial aging (AAA) and staining by black tea. Method: Twenty disk-shaped specimens (were compacted into the custom-made cylindrical plastic mold that had an internal diameter of 10 mm and a depth of 2 mm) were prepared for each composite resin type (3M Z350, Tokoyama palfique and shofu Beautifil II) for a total of 60 specimens, each composite group was divided into two subgroups according to the polishing system (n=10) (Shofu super-snap polishing disks and Eve Diacomp Plus Twist wheel). Color parameters (L*, a*, and b*) and surface roughness were measured before and after accelerating artificial aging (2000-4000 thermal cycle) and staining. Results: It was observed that all resin-based materials showed an increase in color change value and surface roughness values after 2000 thermal cycles. while after 4000 thermal cycles only the surface roughness value decreased in all resin-based materials. Conclusion: all resin-based materials showed clinically acceptable color stability and surface roughness &gt;0.2 µm) after (2000 thermal cycle) and staining. Keywords: color stability, surface roughness, thermal cycle, staining.

Microhardness, Surface Roughness, and Wear Resistance Enhancement of Reinforced Conventional Glass Ionomer Cement Using Fluorinated Graphene Oxide Nanosheets.

Conventional glass ionomer cements (GICs) have been considered the most prevalent restorative material however; the reduced mechanical qualities and decreased wear resistance have been the main challenges facing their wide clinical application. This study was designed to assess the mechanical properties of fluorinated graphene (FG) oxide-modified conventional GIC. Composites of FG/GIC samples were prepared using (Medifil from PROMEDICA, Germany, shade A3) at different concentrations (0wt%) control group and (1wt%, 2wt% and 3wt% FG) groups using cylindrical molds (3mm × 6mm). FG was prepared using hydrothermal technique and characterized using XPERT-PRO Powder Diffractometer system for X-ray diffraction analysis and JEOL JEM-2100 high resolution transmission electron microscope. Vickers' hardness and wear resistance of GI samples were measured. Mechanical abrasion was performed via three-body tooth brushing wear test using ROBOTA chewing simulator coupled with a thermocycling protocol (Model ACH-09075DC-T, AD-Tech Technology Co., Ltd., Leinfelden-Echterdingen, Germany). Comparisons between groups with respect to normally distributed numeric variables were performed using one-way analysis of variance test followed by posthoc test. While paired t-test was utilized for comparing data within the same group. The surface roughness values of GICs (1wt% FG) and (2wt% FG) composites were significantly lower than those of the control and 3wt%FG groups. Vickers' hardness numbers were significantly higher in FG/GICs composites than in the control group (p≤0.05). GIC/FG combinations have sufficient strength to resist the occlusion stresses with improved hardness as compared with conventional GIC. GIC/FG appeared to be a promising restorative material.

INFLUENCE OF STEEL FIBRES OF CRIMPED AND HOOKED-END SHAPE ON THE MECHANICAL PROPERTIES OF PORTLAND CEMENT

Cement mortar without fibers might crack due to shrinkage or volume changes. Cracking in cement mortar leads to elastic deformation. The development of these cracks causes elastic deformation of cement mortar. This study examined the influence of two steel fibers' geometrical forms (crimped and hooked with just one end) in different amounts by volume (Volume fraction = 0.25%, 0.5%, and 0.75%) on the cement mortar's mechanical features. Among the characteristics were splitting, compressive as well as flexural strength. The samples were prepared, poured into cubic molds for compressive strength testing cylindrical molds used for splitting strength testing, and prismatic molds for flexural strength testing, and processed at various times 3, 14, and 28 days before the tests. According to the findings, the highest increase was obtained after adding 0.75% of crimped fibers, the compressive strength increased by 13.3 %21.29%, and 44.8%, for 3,14.28 days respectively, and split tensile strength increased by 66.17%,68.9%, and 79.48% for 3.14 and 28 days respectively and flexural strength increased by 72 %,91% and 92% for 3.14 and 28 days, respectively.

Comparison of the microhardness of lowviscosity bulk-fill composite resins

The aim of this study is to compare the microhardness of five different low-viscosity bulk-fill composites. The bulk-fill composites used in the study; Estelite Bulk-fill flow (EBF), Filtek Bulk-fill (FBF), SureFil SDR flow (SDR), Tetric EvoFlow Bulk fill (TEFBF), X-tra Base (XBF). Cylindrical molds with a diameter of 5 mm and a height of 4 mm were used for the Vicker's Micro Hardness (VMH) test. Bulk-fill composite resins were placed in these molds at once. The polymerization of the composites was achieved for 20 seconds with the LED light curing. A total of 50 composite discs were prepared (n=10). Then the microhardness of the top and bottom surfaces was measured using MVK-H1 Microhardness Tester (Akashi Co, Tokyo, Japan. Depth of polymerization of each sample was recorded. Data were analyzed by using the Kruskal Wallis H and Mann Whitney-U tests. The bottom and top surface hardness values of the XBF composite samples (43.82±0.95 MPa, 47.87±0.59 MPa) were statistically significantly higher than the other bulk-fill composite samples (p&lt;0.001). The bottom and top surface hardness values of the FBF composite (27.85±0.56 MPa, 22.05±1.40 MPa) were found to be statistically lower than other bulk-fill composite samples (p&lt;0.001). Among the low-viscosity bulk-fill composites used in the study, except for FBF, the VMH values of the others were found to be above 0.80, and it was observed that they reached sufficient microhardness.

INVESTIGATE OF INFLUENCE PERFORATED PLATE ON DETERMINATION OF TRANSVERSAL PERMEABILITY ON REINFORCED FIBER

Polymeric composite materials can be build in different forms, resulting in different mechanical properties, with numerous industrial applications. Traditionally, they have been largely used in the automotive, naval and aerospace industries. A major concern in polymeric composites manufacture is related with the determination and control of the reinforcement and resin physical properties. They are responsible for the final composite mechanic properties and, if not correct defined, will result in defective composites. Reinforcement permeability is one of these physical properties that, in some cases, are difficult to be kept within the project specification. More specifically, for the case of the transverse permeability, its corrected determination is reported in literature as being considerably more difficult to experiment than the in-plane permeability. The most common experiment for transverse permeability determination is built with a cylindrical mold on which the reinforcement is positioned (and compressed) between two perforated plates. A fluid is forced transversely through the reinforcement, volumetric flow rate and pressure drop are measured, and the Darcy's Law is used to determine the permeability. In this experiment, flow is assumed rectilinear, and the holes of the perforated plates are ignored in the Darcy equation. It is known that size, number e position of these holes may influence the permeability determination, however this problem is not commonly discussed in literature. In this work it is presented a numerical study about the influence of the geometry of the perforated plates on the corrected determination of the reinforcement transverse permeability. The reinforcement region is molded as a porous medium and the two fluid flow (air + resin) is formulated with the Volume of Fluid (VoF) method. GMSH software was used to created and discretize the geometry and OpenFOAM software, more specifically using the interFoam solver, was used to solve the flow problem, determining pressure drop and flow rate inside the mold. Results have shown that correct determination of the transverse permeability is highly dependent on perforate plates geometry.

A novel experimental method for measuring the direct tensile strength of concrete

Abstract This study deals with the development of a load-converting device designed for measuring the direct tensile strength of the concrete. In this regard, a new testing technique based on a novel testing device and modified cylindrical (Ø 100 × 200) molds for the preparation of concrete samples is explained. The embedded rod method was adopted to transmit the uniaxial tensile load to the specimens using the universal compression machine and the current converting device. In order to examine the reliability of the suggested test method, a comparison with indirect tensile methods (splitting and three-point loading flexural tests) was made. The results show that the tensile strength of the tested specimens is lower for the direct tensile test obtained by the proposed test setup than for the flexural test and closer to the strength results obtained from the splitting test. As expected, all the specimens tested using the introduced test method demonstrated a sudden and unique fracture in the middle portion. Additionally, no slippage of embedded bars was noticed during the test.

A Comparative In Vitro Analysis of Antimicrobial Effectiveness and Compressive Strength of Ginger and Clove-Modified Glass Ionomer Cement.

Background Glass ionomer cement (GIC) is widely recognized for its self-adhesive characteristicsand biocompatibility, making it commonly used as a restorative material. However, challenges related to limited antibacterial effectiveness and relatively low mechanical properties have hindered its widespread clinical use. Cloveand ginger are recognized for their potent antimicrobial activity against numerous pathogenic microorganisms. The present study aims to enhance the clinical applicability of GIC by modifying it with clove and ginger extract. Aim The objective of the study is to assess the antimicrobial effectiveness and compressive strength of GIC modified with ginger and clove extract. Materials and methods Ginger and clove extracts were prepared and incorporated into conventional GIC at three concentrations for each, creating ginger-modified GIC groups (Group A, Group B, and Group C) and clove-modified GIC groups (Group D, Group E, and Group F), with Group G as the control (conventional GIC without modification). The antimicrobial assessment was conducted on disc-shaped GIC specimens (3.0 mm height x 6.0 mm diameter) prepared using molds. Bacterial strains were used to evaluate antimicrobial properties, with minimum inhibitory concentration (MIC) assays conducted at intervals of one to four hours for both modified and unmodified groups. Compressive strength specimens were prepared using cylindrical molds (6.0 mm height × 4.0 mm diameter), according to the ISO (International Organization for Standardization) guidelines. The evaluation was conducted using a Zwick universal testing machine (ElectroPuls®E3000, Instron, Bangalore, India), with the highest force at the point of specimen fracture recorded to determine compressive strength. Statistical analysis was conducted utilizing a one-way analysis of variance (ANOVA) alongside Tukey's post hoc test, with a significance threshold set at p < 0.01. Results The antimicrobial effectiveness of clove and ginger-modified GIC was assessed through a MIC assay, revealing a statistically significant improvement in antimicrobial potency against Streptococcus mutans and Lactobacillus within the modified groups compared to the control group (p < 0.01). Increased extract concentration correlated with enhanced antimicrobial activity. Clove-modified GIC exhibited superior antimicrobial efficacy compared to ginger extract. Compressive strength was higher in clove-modified GIC groups (p < 0.01), with Group F showing a maximum value of 175.88 MPa, while other modified groups demonstrated similar results to the control, with a value of 166.81 MPa (p > 0.01). Conclusion The study concludes that both clove-modified GIC and ginger-modified GIC exhibited antimicrobial activity against Streptococcus mutans and Lactobacillus species. The antimicrobial activity was notably higher in clove-modified GIC compared to ginger-modified GIC. Additionally, the compressive strength of clove-modified GIC surpassed all other groups. Thus, clove-modified GIC emerges as a promising restorative material for addressing recurrent caries. Future investigation is necessary to assess the long-term durability of the material.

Effect of Radiotherapy and Taper of Root Canal Preparation on the Biomechanical Behavior of Mesial Roots of Mandibular Molars

IntroductionThis study aimed to investigate the effect of radiotherapy and taper of root canal preparation on the biomechanical behavior of mesial roots of mandibular molars. MethodsEighty mandibular molars with 2 canals in the mesial root were randomly allocated into 2 groups (n = 40): one group underwent irradiation (60 Gy), while the other did not. Subsequently, the mesial roots were sectioned and each group was subdivided into 5 subgroups (n = 8), according to the preparation taper: no preparation (control); 25.03; 25.04; 25.06; and 25.08. All groups were considered homogeneous regarding their dimensions, weight, and morphology. The prepared specimens were embedded in cylindrical plastic molds and subjected to a cyclic fatigue test. A failure analysis was performed according to the extension and course of the fractures. Two-way ANOVA, Tukey's post-hoc, Fisher's exact, and Kaplan–Meier tests were conducted to evaluate the obtained data (α = 5%). ResultsFatigue resistance decreased as the taper of the preparation increased (P < .05). Preparation 25.03 presented significantly higher values only than 25.08 (P < .05), while 25.04, 25.06, and 25.08 were considered similar (P > .05). Irradiation significantly reduced the biomechanical performance (P < .05). Survival analysis corroborated these findings. There were no differences in the distribution of fracture types among the groups (P > .05). ConclusionThe biomechanical behavior of the mesial roots of the mandibular molars decreased significantly in the face of irradiation and as the taper of the preparation increased.