Brass Mold Research Articles

Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials.

This study aimed to evaluate the effect of adding different concentrations of silver nanoparticles (AgNPs) on the flexural strength and microhardness of various denture base materials. For this study, a total of 60 specimens were used and divided into equal groups. The first group consisted of heat-cured acrylic resin (Vertex-Germany), while the second group consisted of thermoplastic resin (Breflex 2nd edition, Germany). The samples were created using a split brass mold with dimensions of 65 × 10 × 2.5 mm, in accordance with the specifications of the American Dental Association (specifically No. 12 for flexural and microhardness). Following this, the samples were divided into three groups (A, B, and C) based on different concentrations of AgNPs (0, 2, and 5%). The flexural and microhardness of the samples were assessed using a universal testing machine and the Vickers hardness test, respectively. The data were gathered, organized, and analyzed using statistical methods. The flexural strength findings showed a significant difference between the two groups. Also, there was a considerable decrease in the average value of the acrylic group as the concentrations of AgNPs rose, while the flexural strength of the thermoplastic group notably improved. Regarding microhardness, the results showed a significant difference between the two groups. It showed that the mean value of both groups increased with increasing concentrations of AgNPs. Within the limitations of laboratory testing conditions of this study, it was discovered that AgNPs negatively impact the flexural strength of acrylic resins. Furthermore, an increase in the concentration of AgNPs was found to be directly related to the flexural strength of thermoplastic resin and the microhardness of both groups. The concentration of AgNPs has a significant impact on certain mechanical properties of denture base materials, but it is important to consider their potential toxicity. How to cite this article: El-Hussein IG. Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials. J Contemp Dent Pract 2024;25(5):417-423.

Erosive Effect of Canned Juices and Soft Drinks on Surface Roughness of Restorative Materials Used in Pediatric Dentistry: An Ex Vivo Study.

To evaluate and compare the effect of fruit juice (orange) and cola drink (noncarbonated) on the surface texture of composite (3M ESPE Filtek Bulk Fill) and glass ionomer cement (GIC) (ChemFil Superior). A total of eighty pellets each were prepared with composite (3M ESPE Filtek Bulk Fill) and GIC (ChemFil Superior) material using a brass mold with an inner diameter of 3 mm and a thickness of 3 mm according to the manufacturer's instructions. Around 10 pellets of each material were placed in airtight plastic containers. The baseline surface texture value was obtained by profilometer. An 8-day immersion regime was carried out according to Maupome et al. After the 8-day test period, pellets were reevaluated for surface texture final value. The values were statistically analyzed. A statistically significant lower surface roughness of composite restorative material was observed when treated with high-concentration orange juice and medium-concentration. Conversely, a statistically significant lower surface roughness of GIC restorative material was observed when it was treated with the low-concentration group, high-concentration orange juice, and medium-concentration orange juice. The surface roughness patterns of restorative materials increased as the number of immersion regimes increased. Vishwanathaiah S, Maganur PC, Khabrany HM, et al. Erosive Effect of Canned Juices and Soft Drinks on Surface Roughness of Restorative Materials Used in Pediatric Dentistry: An Ex Vivo Study. Int J Clin Pediatr Dent 2024;17(7):807-811.

Effect of natural silk fibers and synthetic fiber-reinforced composites on the cytotoxicity of fibroblast cell lines.

Synthetic fibers have many benefits in clinical practice; however, they cause microplastic pollution, and their unaffordable price increases treatment costs. Natural silk fibers require biocompatibility assessment. This study investigated the effects of natural and synthetic fiber-reinforced composites (FRCs) on the cytotoxicity of fibroblast cell lines. Three commercial synthetic fibers (polyethylene, quartz, and E-glass) and two silk fibers from Bombyx mori and Samia ricini cocoons were employed. These fibers were made into FRC samples (n=6) by impregnation in flowable composite using a brass mold (25×2×2 mm). NIH/3T3 mouse fibroblasts were cultured in Dulbecco's modified eagle medium, supplemented, and seeded in 2×104 cells/mL. They were stored at 37 °C under 5% CO2 for 24 hours. The FRC samples were made into powder, eluted in dimethylsulfoxide, continued with PBS, supplemented with Dulbecco's modified eagle medium (DMEM), and exposed to cells for 24 hours. Blank (medium only) and control (cells and medium) samples were included. Subsequently, MTT was added for 4 h and read by enzyme-linked immunosorbent assay (λ=570 nm). Cell viability (%) was calculated and analyzed using one-way ANOVA (α=0.05). All groups of FRCs showed>80% cell viability. One-way ANOVA showed no significant difference between FRC groups regarding the viability of fibroblast cell lines (P>0.05). Both natural silk and synthetic fibers exhibit low cytotoxicity to fibroblast cell lines. B. mori and S. ricini silk fibers showed the potential to be used as alternative synthetic fibers.

Utilization of cross‐correlation function for assessment of replication quality in ultrasonic embossing of microchannels on polymethyl methacrylate

AbstractUltrasonic embossing—a process where a horn vibrating at 20–30 kHz compresses on a thermoplastic substrate sitting on a mold to replicate the features on the mold to the substrate—is a promising method for fabricating microchannels on thermoplastics due to reduced cycle time and relatively low equipment cost. Replication quality in ultrasonic embossing has been investigated in the literature by primarily referring to the replication depth. However, this approach does not fully reflect the fidelity between the mold and the replicated feature, especially at the side walls, which are typically designed to be vertical in microchannels. We propose using cross‐correlation—a method that quantifies the similarity between two signals by measuring the overlap of their patterns—between the derivative of the mold profile and the embossed profile as a figure of merit that accurately reflects the fidelity of the side wall. For testing purposes, we embossed straight microchannels on polymethyl methacrylate (PMMA) using micron‐scaled protrusions on a brass mold fabricated by CNC milling. The mold comprised 100, 300, and 1000‐μm‐wide protrusions of same designed height of 300 μm, resulting in aspect ratios (AR) of 3, 1, and 1/3, respectively. Cross‐correlations between the derivatives of the profiles ranged between 0.50 and 1.00, while cross‐correlations between the profiles were greater than 0.97 in all cases, showing the sensitivity imposed by utilizing the derivatives. Setting average of all cross‐correlation values (0.8) as the quality threshold, we observed that high AR (3) features were replicated at low quality, while low AR (1/3) features were replicated at high quality, regardless of the process parameters. In replicating unit AR features, the process parameters were observed to affect the quality, where the combination of vibration time and pressure was the most significant compared to individual effects of the parameters.Highlights Parameters' effect on replication of varied aspect ratio features was assessed. Assessment was carried out by cross‐correlating mold and channel profiles. Cross‐correlating derivatives of profiles provide a more sensitive means. General rules for replication quality in ultrasonic embossing were driven.

Staining ability of herbal tea preparations on a nano-filled composite restorative material - an in-vitro study.

Background: Discoloration of tooth-colored restorations due to various factors is one of the principal causes behind the failure of aesthetics. There has been an surge in the consumption of herbal beverages in recent times and the dietary factors play a potential role in the discoloration tooth-coloured restorations. This study was done to juxtapose the staining ability of green tea (GT), moringa tea (MT), and hibiscus tea (HT) on a nano-filled composite restorative material. Methods: The study was conducted in-vitro on composite samples prepared using moulds. 112 discs were prepared from Filtek TM Z350XT composite using a brass mould lined with mylar strips. Samples were divided into GT, MT, HT, and artificial saliva (AS) groups and immersed in freshly prepared beverages for 15 minutes each day for 45 days. Digital reflectance spectrophotometer was utilized to record color at baseline, 30, and 45 days. Repeated-measures ANOVA with a post-hoc Bonferroni test was used to compare groups within each group. ANOVA with a post-hoc Games Howell test was used to compare mean differences in ΔE among the groups. Results: Maximum discoloration was observed in the GT, followed by HT and MT, with the least being in the AS group at the end of 30 and 45 days (P<0.001 and P<0.001) respectively. Conclusions: The universal nano-filled composite material showed clinically detectable discoloration when exposed to Green Tea, Hibiscus Tea, and Moringa Tea which increased with time. Herbal beverages have the potential to cause discoloration of the composite resin which is often the choice of material for anterior aesthetic restorations.

Surface Micro-Hardness and Wear Resistance of a Self-Adhesive Flowable Composite in Comparison to Conventional Flowable Composites.

Objectives: The durability of composite restorations is directly affected by the mechanical properties of the composite. The aim of this study was to evaluate the hardness and wear resistance of self-adhesive flowable composite (SAF) in comparison with conventional flowable composites. Materials and Methods: In this in vitro study, 50 composite specimens were prepared in brass molds with 10mm ×10mm ×2mm and divided into five groups (n=10). Specimens included three conventional flowable composites (Grandio flow, Filtek flow and Admira fusion flow), one self-adhering flowable composite (SAF, Vertise flow) and a microhybrid composite (filtek z250). After polishing, the micro-hardness of the specimens was measured in a Vickers hardness device, and the specimens were then subjected to 5000, 10000, 20000, 40000, 80000 and 120000 wear cycles in a wear tester. One-way ANOVA/Games-Howell, Kruskal Wallis, and Friedman tests were used for statistical analysis. The significance level was set at P<0.05. Results: The surface micro-hardness of the SAF was significantly lower than that of the microhybrid composite (P=0.01). There was no significant difference between the surface hardness of the different tested flowable composites (P>0.05). Also, the wear resistance of the studied composites was not significantly different in various cycles (P>0.05). Conclusion: Based on our results, SAF would not be an ideal substitute for conventional flowable composites in high-stress areas.

Fluoride release by restorative materials after applying surface coating agents.

The prompt use of an enamel surface covering reagent is advised to safeguard the dental restorative substance from mishaps. Therefore, it is of interest to assess the fluoride emitting capabilities of standard GIC, and Zirconomer cement together with surface coverings and without surface coverings. The conventional GIC cement was part of experimental category A while Zirconomer cement was part of category B. For every experimental categories, a set of sixty brass mould prototypes in the form of disc with dimensions: diameter (6±0.1mm) and thickness (2±0.1 mm) were created and subsequently covered with Teflon strip in accordance with the package recommendations. Also, for both experimental categories, such pellets were randomly allocated to three sub-categories of 20 each. For one category petroleum jelly was administered with a cotton bud and then delicately dried under airflow (A3 subcategory and B3 subcategory); for another sub-category G-Coat was laced through a micro-tip dispenser and light treated for twenty seconds (A2 subcategory and B2 subcategory); the rest 20 specimens were left without any coating (A1 subcategory and B1 subcategory). It was observed that in subcategory A1 and A3 there was continuous decline in emission of fluoride ion as the days progressed. However there was an increase in emission of fluoride in A2 subcategory on moving to day 5 from day 1. However, from day 5 onwards decline in fluoride emission was observed in A2 subcategory. It was concluded that both materials studied (GIC and Zirconomer) exhibited fluoride emission whether or not they were surface-coated for protection.

Staining ability of herbal tea preparations on a nano-filled composite restorative material – an in-vitro study

Background: Discoloration of tooth-colored restorations due to various factors is one of the principal causes behind the failure of aesthetics. There has been an surge in the consumption of herbal beverages in recent times and the dietary factors play a potential role in the discoloration tooth-coloured restorations. This study was done to juxtapose the staining ability of green tea (GT), moringa tea (MT), and hibiscus tea (HT) on a nano-filled composite restorative material. Methods: The study was conducted in-vitro on composite samples prepared using moulds. 112 discs were prepared from FiltekTM Z350XT composite using a brass mould lined with mylar strips. Samples were divided into GT, MT, HT, and artificial saliva (AS) groups and immersed in freshly prepared beverages for 15 minutes each day for 45 days. Digital reflectance spectrophotometer was utilized to record color at baseline, 30, and 45 days. Repeated-measures ANOVA with a post-hoc Bonferroni test was used to compare groups within each group. ANOVA with a post-hoc Games Howell test was used to compare mean differences in ΔE among the groups. Results: Maximum discoloration was observed in the GT, followed by HT and MT, with the least being in the AS group at the end of 30 and 45 days (P&lt;0.001 and P&lt;0.001) respectively. Conclusions: The universal nano-filled composite material showed clinically detectable discoloration when exposed to Green Tea, Hibiscus Tea, and Moringa Tea which increased with time. Herbal beverages have the potential to cause discoloration of the composite resin which is often the choice of material for anterior aesthetic restorations.

PolyJet-Based 3D Printing against Micromolds to Produce Channel Structures for Microchip Electrophoresis.

In this work, we demonstrate the ability to use micromolds along with a stacked three-dimensional (3D) printing process on a commercially available PolyJet printer to fabricate microchip electrophoresis devices that have a T-intersection, with channel cross sections as small as 48 × 12 μm2 being possible. The fabrication process involves embedding removable materials or molds during the printing process, with various molds being possible (wires, brass molds, PDMS molds, or sacrificial materials). When the molds are delaminated/removed, recessed features complementary to the molds are left in the 3D prints. A thermal lab press is used to bond the microchannel layer that also contains printed reservoirs against another solid 3D-printed part to completely seal the microchannels. The devices exhibited cathodic electroosmotic flow (EOF), and mixtures of fluorescein isothiocyanate isomer I (FITC)-labeled amino acids were successfully separated on these 3D-printed devices using both gated and pinched electrokinetic injections. While this application is focused on microchip electrophoresis, the ability to 3D-print against molds that can subsequently be removed is a general methodology to decrease the channel size for other applications as well as to possibly integrate 3D printing with other production processes.

Effect of Composite or Ceramic Thickness on the Polymerization Hardness of 5 Different Dual-cured Resin Luting Cements

Objective: The aim of the present study was to evaluate the influence of ceramic and composite thickness on polymerization hardness of five different dual-cure resin cements. Materials and Methods: A total of 100 disc-shaped spacer, 10-mm in diameter and five varying thicknesses (1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm) were fabricated from ceramic and composite materials. Dual-cure resin cement specimens with 8-mm diameter were prepared using metal brass mold and activated by light beneath the composite and ceramic disc shaped spacers. A total of 100 specimens of five different dual-cure resins (RelyX, Variolink, NX3, Calibra, Panavia F2.0) were prepared. Knoop hardness of each dual-cure resin cement was measured at five different point using a microhardness device with a 500 gm load, after 1 hr, 1 day, and 1 week polymerization. All data were statistically evaluated using one-way ANOVA. Results: Multivariate analysis of variance revealed significant differences in hardness of specimens dual-cured under composite resin or ceramic spacers and different time intervals (P&amp;lt;.001). Specimens cured through composite resin spacers showed less hardness values than ceramic spacers, with increasing thickness of the spacer. Also increasing the thickness of the composite or ceramic spacers produced a statistically significant decrease in microhardness of the dual-cure cements (P&amp;lt;.05). Conclusions: Hardness values significantly reduced when composite spacers were thicker than 2 mm and ceramic spacers thicker than 3 mm. Dual-cured resin cements are needed to be improved to achieve sufficient degree of hardening under composite and ceramic restorations. Different commercially available brands have different polymerization properties.

The comparative evaluation of various additives on setting time and compressive strength of MTA Plus: An in vitro study

Background and Objectives: Mineral trioxide aggregate (MTA), being a near-ideal retrograde filling material, has the greatest disadvantage of longer setting time, which limits its use in a certain clinical situation. A novel MTA, known as MTA Plus, claims to have a finer particle size and is marketed with an additional anti-washout gel. This study was undertaken to compare the setting time and compressive strength (CS) of MTA Plus with various additives.Materials and Methodology: MTA Plus powder was mixed with following additives such as 5% CaCl2 solution, 10% CaCl2 solution, phosphate-buffered saline, 80% distilled water/20% propylene glycol, saline, lidocaine HCl, 15% sodium phosphate monobasic, 3% sodium hypochlorite gel, and proprietary gel with MTA Plus in the ratio of 3:1 by weight. Setting time was evaluated using Vicat apparatus using a brass mold with an internal diameter of 10 mm and height of two millimeters. CS was evaluated using an Instron machine using a split brass mold with an internal diameter of Four millimeters and height of Six millimeters.Results: The results showed that 15% sodium hydrogen phosphate and MTA Plus gel significantly decrease the setting time of MTA Plus. MTA Plus gel set cement gave the highest value of CS among all groups of additives studied.Interpretation and Conclusion: Additives used in the given study had an influence on physical property like setting time and mechanical property like CS of MTA Plus.

In-vitro Comparative Evaluation of Flexural Strength and Depth of Cure of Bulkfill Composite

Aims and objectives: Bulkfill composite resins have been used for the posterior restorations in an attempt to speed up the restorative process. Here 4 to 5mm thickness of composite resins can be placed andcured in asingle step so that time consuming layering technique can be eliminated. The purpose of this study was to investigate the flexural strength and depth of cure of two bulk fill composites and to compare it with a universal composite. Materials and method: Two bulk fill composites (Sonic fill and Filtekbulkfill) and one universal composite (Filtek Z350 XT) were used. Ten samples per group were made using rectangular split brass mold following ISO standard 4049 to measure the flexural strength. Each sample was then subjected to three point bend test using universal testing machine until failure occurred. For depth of cure measurements, ten samples per group were made using cylindrical brass mold and were subjected to acetone shake test for 30 sec. The dimensions of the samples were measured using Vernier callipers and compared. One-way analysis of variance followed by Tukey’s post-hoc test was used to determine the statistical differences among groups at significance of p&lt;0.05. Results: Sonicfillgave highest flexural strength value and Filtek Z350 XT the least. There was no statistically significant difference between the flexural strength of Filtekbulkfill and Filtek Z350 XT. For depth of cure, Filtekbulkfill showed higher value than other tested groups. Conclusion: All the tested materials showed significantly higher flexural strength values than the minimum flexural strength (80MPa) that is required for use in stress bearing areas. Sonicfill composite produced highest value of flexural strength than other composites, which may bedue to its increased percentage of filler content. For depth of cure, both the tested bulkfill composites showed lesser value of depth of cure than that claimed by manufacturers .

Effect of Green, Tulsi, and Areca Teas on the Color Stability of Two Composite Resin Materials - an in vitro Spectrophotometric Analysis.

ObjectiveTo compare the effect of Green, Tulsi, and Areca teas on the color stability of two composite materials on the 30th and 60th days.Materials and MethodsTwo light cure composite restorative materials, Brilliant EverGlow (Group 1) and Brilliant NG, (Group 2) with different resin and filler characteristics were selected. The test solutions selected were Green tea, Tulsi tea, Areca tea, and artificial saliva (control group). In total, 104-disc shaped specimens were fabricated using a custom made brass mold as per the manufacturer instructions. All specimens were put in storage for rehydration and complete polymerization at 37°C in distilled water for 24 hours. Specimens of each composite material were randomly divided into four subgroups of 13 samples. Tea solutions were freshly prepared, and specimens were immersed in the respective solutions every day for 15 minutes for 60 days. Specimens were stored in artificial saliva after the immersion regimen. The color evaluation was done before immersion, on the 30th and 60th day, using a digital reflectance spectrophotometer.ResultsAt 30 days, Group 1 specimens immersed in Areca and Green teas showed significantly higher mean values than those in control and Tulsi tea. At 60 days in Group 1, specimens in Areca tea showed significantly higher mean value, followed by Green tea, Tulsi tea, and control. At 30 and 60 days in group 2, specimens in control had significantly lower mean values than other tea preparations. Group 1 showed a higher mean difference in ΔE than Group 2 specimens immersed in Green and Areca teas at 30 days (P=0.001 and 0.001) and 60 days (P=0.001 and <0.001), respectively.ConclusionAll herbal tea preparations exhibited staining potential, which increased over time, and Areca tea showed the highest staining potential. Understanding the staining potential of newer tea preparations on recent composite materials helps the clinician to choose the right restorative materials.

Comparative evaluation of the depth of cure and surface roughness of bulk-fill composites: An in vitro study.

Composites are in great demand due to the esthetic needs of the patients, which explains a wide variation in the types of available composites. However, the mechanical strength of the materials is questionable. Therefore, the mechanical properties of the newly available bulk-fill composites have been tested. The main objective of the study was to compare the depth of cure (DOC) and surface roughness of 3 different bulk-fill composites: X-tra fil® (XTF), Tetric EvoCeram® Bulk Fill (TEC) and Beautifil® Bulk Restorative (BBR). Fifty-seven (n = 19 in each group) samples were made using brass molds. All samples were subjected to Vickers hardness testing and profilometry. The one-way analysis of variance (ANOVA) test was used for the data analysis, followed by Tukey's post hoc test. The differences in the mean surface microhardness values of the materials were statistically significant (p < 0.001), with XTF showing the highest value. The TEC composite showed a higher surface roughness as compared to BBR and XTF. The results of the present study indicate that variations in the filler size and amount significantly influence the DOC and surface roughness of dental composites. Among the tested composites, the multi-hybrid composite exhibited superior DOC (XTF), whereas the nanohybrid composite exhibited superior surface finish (TEC).

Evaluation of the Effect of Household Cleansers on the Color Change of Two Types of Permanent Soft Liners: An In Vitro Study

Many patients use household cleaners to clean denture which can cause discoloration and damage soft liners. The purpose of this study was to evaluate the effect of household cleansers on the color change of two types of permanent soft liners. Methods: In this interventional study, 80 permanent silicone soft liners, including 40 heat-cured liners (Molloplast-B, Detax Gmbh & Co. KG, Ettlingen, Germany) and 40 self-cure liners (Mucopren soft, Kettenbach GmbH & Co. KG, Eschenburg, Germany) were made in brass molds with dimensions of 15×2 mm in accordance with the manufacturer's instructions. The samples were immersed in distilled water for 24h and the initial color was determined using a colorimeter. Then, each group (n=10) was immersed for 8h daily in 2.5% vinegar, 2.5% hypochlorite, 2.5% hand washing liquid, and distilled water (control). Color measurements were performed after 7 and 30 days of immersion in solutions and data were analyzed using ANOVA, independent t-test, and Tukey's post hoc tests. Results: In distilled water, hypochlorite, and vinegar, the mean color change after one month was significantly lower in Molloplast-B than Mucopren (P=0.042, P<0.001, P=0.002); however, in Hand washing, the difference was not significant (P=0.780). Conclusion: The mean color change in Mucopren in all cleansers was higher than Molloplast-B, and the highest change in color was observed in both liners in hypochlorite.

Comparison of the Properties of Glasses Made from Two Different Bottom Ashes

Bottom ash is a waste byproduct generated from the combustion or incineration of materials such as coal and household waste. It is a mixed oxide powder of variable composition, though typically high in silica. As a low-cost, readily available material, it has found applications primarily in construction for use as backfill. As a silica-rich, mixed oxide powder though, it may also have glass forming ability. This research studied the possibility to use domestically produced bottom ash powder in glass making. Two bottom ash powders were used, one from a waste incinerator (Phuket) and the other from a coal-fired electric plant (Mae Moh Power Plant, Lampang). The bottom ash was milled into a fine powder and melted within the temperature range of 1300-1500 oC, for 2 hours. The melts were cast in a brass mold and then annealed at 500 oC for 2 hours. It was found that both bottom ashes could successfully produce glasses. The Vickers hardness, refractive index and specific gravity of the glasses will be discussed.

Effects of Bleaching Agents on the Microhardness and Surface Roughness of Bulk Fill Composites

ABSTRACT Aim The aim was to compare the effect of 10 and 20% carbamide peroxide (CP) on microhardness (MHN) and surface roughness of two commercially available bulk fill composites (X-tra fill Bulk Fill and Tetric EvoCeram Bulk Fill). Materials and methods A total of 50 specimens with both type composites were prepared using brass molds of inner diameter 10 mm and a height of 4 mm. Each type of composite was further divided into three groups, control group stored in artificial saliva for 14 days, other groups bleached with 10 and 20% CP respectively, for 14 days. Microhardness of the composite resin was tested with a Vickers hardness tester, whereas surface roughness was tested with profilometer. Results All the analysis was performed using Statistical Package for the Social Sciences version 18. The value of p &lt; 0.05 was considered statistically significant. Both 10 and 20% CP significantly reduced MHN of experimental composite resins. However, the mean surface roughness was significantly higher in X-tra fill Bulk Fill than Tetric EvoCeram Bulk Fill at 20% CP concentration. The mean MHN of Tetric EvoCeram was reduced when compared with X-tra fill at 20% CP. Conclusion There was a significant reduction in the MHN of restorative materials observed after exposure to CP under a clinically simulated bleaching regimen. However, increase in surface roughness was seen only at 20% CP. Clinical significance The physical properties, such as MHN and surface roughness have a crucial effect on the longevity of restorations and, moreover, on the esthetic demands of patients, but they may be compromised by bleaching treatments. The aim of this research paper was to assess the reaction of home bleaching agents on the physical properties of two Bulk Fill composite resin restorative materials. How to cite this article Francis G, Pradeep K, Ginjupalli K, Saraswathi V. Effects of Bleaching Agents on the Microhardness and Surface Roughness of Bulk Fill Composites. World J Dent 2017;8(3):196-201.

The effect of short polyethylene fiber with different weight percentages on diametral tensile strength of conventional and resin modified glass ionomer cements.

BackgroundThe aim of this study was to investigate the effect of polyethylene fiber on diametral tensile strength of conventional and resin modified glass ionomer cements.Material and Methods60 specimens in 6 groups (n=10) were prepared. In group 1 conventional glass ionomer (Fuji GC) and in group 2 resin modified glass ionomer (Fuji LC) were as control groups. In group 3 and 4 conventional glass ionomers mixed with short polyethylene fibers in proportion of 1 wt% and 3 wt%, respectively. In fifth and sixth groups, resin modified glass ionomer and short polyethylene fibers were mixed in 1 and 3% wt, respectively. Samples were prepared in a round brass mold (6.5×2.5 mm). After thermo-cycling, the diametral tensile strength of the specimens were tested and data were analyzed with ANOVA and post-hoc tests (p<0.05).ResultsDiametral tensile strength of both conventional and resin modified glass ionomer cements increased after mixing with polyethylene fiber (p<0.001). Also, reinforcement occurred as the mixing percentage increased from 1% wt to 3% wt in either conventional and resin modified glass ionomer (p<0.001).ConclusionsThe polyethylene fiber was shown to have a significant positive influence on diametral tensile strength of two types of glass ionomers. Key words:Conventional glass ionomer, diametral tensile strength, polyethylene fiber, resin modified glass ionomer.

Comparative evaluation of color stability of four provisional restorative materials: An invitro study

Purpose: The present invitro study was conducted to evaluate and compare the colour stability of four commercially available provisional restorative materials. Methods and Material: In the present study a customized 3 piece brass mold with the middle section of (2mm thick & 7mm diameter) was used to fabricate auto polymerizing bis-acryl resin specimens. 30 samples were prepared for each group and checked for colour stability in coffee and tea. One way Analysis of variance (ANOVA) and post hoc test was done for inter comparison between groups. Results: The findings from the study show the mean reflectance value of structure 2 SC was 22.839 followed by Systemp c & b with 21.699, Integrity with 21.186 and Protemp with a mean of 21.036. Conclusion: Structure 2 Sc (Voco) displayed the more color stability and followed by system c & b and Integrity and protemp 4. Keywords: Colour, Provisional restorative materials, Discoloration, Spectrophotometer

Microsculpturing of Polymeric Surfaces by Compression Molding

Surface micropatterning of polymers is an important process in a large number of applications ranging from microelectronics, sensors design and material science, to tissue engineering and cell biology. In this study a simple and versatile method for manufacturing micro-scale polymer surface patterns has been developed. Micropatterned surfaces of acrylonitrile-butadiene–styrene (ABS) were engineered by compression molding. Two different micropatterned surfaces were fabricated using diverse molds. The first micropatterning was achieved on a brass mold by the intersection of instrumented microindentation traces. The second microsculptured surface was realized through a bronze sintered mold. The morphological aspects and the surface wettability after microsculpturing were investigated. The microsculptured ABS surface produced by the sintered mold shows a higher contact angle compared with those of flat ABS surfaces. From the experimental results, it was found that the intrinsic hydrophobicity of the material is enhanced simply through increasing surface roughness of the solid surface. The method presented is an economical process to fabricate hydrophobic microsculptured surfaces and it is suitable for many kinds of materials.