Composite Resin Samples Research Articles

The effect of different polishing systems on the discoloration of composite resins: examples of commonly consumed beverages

Aims: The aim of this study is to evaluate the color stability of composite resin materials subjected to different polishing systems when exposed to commonly consumed beverages. Methods: In this study, four different composite polishing systems (Zenit, 3M Sof-Lex, Sofu, Kerr) and three types of beverages (Nescafé 3-in-1, Lipton tea bags, and distilled water) were used. A micro-hybrid resin composite (Tokuyama) was selected for the study. A total of 84 disk-shaped composite resin samples (8 mm in diameter and 2 mm thick) were prepared. The samples were divided into four main groups according to the polishing systems used, and further divided into three subgroups based on the beverage types, with seven samples in each subgroup, resulting in a total of 12 study groups. Initial color measurements, as well as measurements taken on days 1, 7, and 28, were recorded using a vita easyshade spectrophotometer. The data were tabulated and statistically analyzed using SPSS 25.0 software, employing one-way ANOVA and Tukey HSD post-hoc tests (p=0.05). Results: Examination of the 28-day staining results revealed a statistically significant difference between the results for distilled water and coffee, depending on the brand (p

UV Exposure Time Optimization for Enhanced Conversion, Hardness, and Flexural Strength in UDMA/TEG-DMA Composite Resins

This study examines the effects of varying ultraviolet (UV) exposure times on the properties of UDMA/TEG-DMA composite resins, focusing on degree of conversion, surface morphology, water absorption, shrinkage, hardness, and flexural strength. Composite resin samples were exposed to UV light for 30, 60, 90, and 120 min. The degree of conversion was assessed using Fourier Transform Infrared Spectroscopy (FTIR). Surface morphology was analyzed via Scanning Electron Microscopy (SEM). Water absorption and shrinkage were measured following standard procedures, while mechanical properties, including hardness and flexural strength, were evaluated using a Vickers hardness tester and a 3-point bending test, respectively. The results indicate that a UV exposure time of 90 min optimizes the composite resin properties, achieving the highest degree of conversion at 77 %, optimal surface morphology, minimal water absorption and shrinkage, and superior mechanical properties, including maximum flexural strength and hardness. In contrast, both shorter and longer UV exposure times detrimentally affected these properties, with prolonged exposure causing thermal degradation and reduced performance. This research underscores the importance of precise UV curing time control to enhance the performance and durability of UDMA/TEG-DMA composite resins, providing valuable insights and practical guidelines for their application in dental and industrial fields. HIGHLIGHTS The incorporation of UDMA/TEG-DMA in composite resin formulations significantly enhanced mechanical properties such as flexural strength and modulus. Exposure to UV light affected the degree of conversion of the resin, impacting its polymerization kinetics and potentially influencing long-term durability. The study revealed notable changes in surface morphology, indicating potential implications for bonding characteristics and aesthetic outcomes. Investigating water absorption and shrinkage behavior provided insights into material stability and dimensional changes over time, critical for clinical longevity and patient satisfaction. GRAPHICAL ABSTRACT

Evaluation of the Effect of Background Color on the Color Change of Composite Resins of Different Translucencies

Aim: To evaluate the effect of background color on the color change evaluation of composite resins of different translucency. Material and Method: In our study, Estelite ∑ Quick (EQ) CE, OA2 and Filtek Ultimate (FU) A2 Enamel, A2 Dentin composites were used. Disc-shaped samples were prepared from the composites of both brands by layering enamel and dentin alone and enamel + dentin (n=10). After preparation, samples were kept in distilled water for 24 hours and then in coloring solution (NescafeClassic) for 10 days. Colors of the composite samples were measured with a spectrophotometer (VıtaEasyshade) on black, white and gray backgrounds after 24 hours (initial) and after coloring. Color change value (ΔE00) was calculated using two measurement values for each background. Color change values of the same composites measured on different backgrounds were compared. Additionally, the ΔE00 values of different translucent tones from the same company were compared on different backgrounds. One-way ANOVA and Tukey's post-hoc tests were used for statistical analysis. (α=0.05). Results: When used layered with dentin, enamel composites consistently showed lower ΔE00 values than enamel composites alone (p<0.05). When comparing ΔE00 values of the same composite resin samples on different background colors, the ΔE00 values measured on black background were found to be higher only for FU enamel compared to the values measured on the other two backgrounds (p<0.05). When different translucent shades from the same company were compared on different backgrounds, the ΔE00 ranking was found to be enamel > dentin >/=mine + dentin for all backgrounds. Conclusion: Different backgrounds did not affect the color evaluation of samples containing an opaque composite resin, dentin composite; however, they did affect the color evaluation of FU enamel, which is a translucent composite resin. When translucent composite resins are layered with more opaque composite resins, more accurate color evaluation can be achieved.

Effect of Inter-Implant Distance on Fracture Resistance of Implant-Supported Provisional Fixed Dental Prosthesis.

This study aimed to identify the ideal interimplant distance for optimum outcome on immediately loaded implant supported prosthesis. Hence this study was taken up to analyze the effect of varying interimplant distance on fracture resistance of implant supported provisional fixed dental prosthesis (FDP). A total of 24 bis-acrylate composite resin samples were prepared. Interimplant distance was present in the metal die for placement of dummy implants at distances of 14 mm, 21 mm, and 30 mm respectively. Wax-up for 3-unit, 4-unit, and 5-unit implant-supported provisional restoration was made. Silicone molds were used for making multiple interim prostheses using bis-acrylate composite material. All samples were subjected to fracture test in the universal testing machine with a crosshead speed of 1 mm/min. All samples were loaded with gradual force starting from 100 N until it fractured. The load was applied at the center of prosthesis. Data was analyzed by one-way analysis of variance and Bonferroni post hoc test. Mean fracture resistance of 3-unit provisional FDP at 14 mm of interimplant distance showed 1342.61 ± 179.15 N. Mean fracture resistance of 4-unit provisional FDP at 21 mm of interimplant distance showed 1420.44 ± 170.37 N. Mean fracture resistance of 5-unit provisional FDP at 30 mm of interimplant distance showed 791.61 ± 203.59 N. Both 14 mm and 21 mm of interimplant distance are suitable span lengths to be considered for the optimum outcome during immediately loading with implant-supported provisional restorations. Limitations of the study were that force application was static in nature and not dynamic and the arch form was not "U" shaped but longitudinal using Bis-Acryl material only with no cantilever. Future studies can be done to evaluate the fracture resistance of bis-acrylate material considering biomechanics and arch form of natural dentition. Distal cantilever should be considered along with different material for fabricating provisional restoration.

BASE SURFACE TEMPERATURE OF BULK FILL RESIN COMPOSITE WITH DIFFERENT THICKNESS

Background: The material thickness is one factor that influences the polymerization of resin composites. Bulk fill resin composite is an efficient dental resin composite restoration material because it can be cured to a thickness of up to 4-5 mm. The thickness of the material can also affect the temperature rise, while maintaining the temperature is very important because a significant increase can damage the pulp. Purpose: This research aimed to analyze the base surface temperature of bulk fill resin composite with different thicknesses. Methods: Thirty bulk fill resin composite samples with a diameter of 5 mm were divided into three groups with different thicknesses, namely group I (3 mm), group II (4 mm), and group III (5 mm). Each group of samples was cured using an LED Light Curing Unit for 20 seconds, and carried out simultaneously with the measurement of the base surface temperature using a type-K digital thermocouple. Data analyzed using One Way ANOVA and LSD post hoc tests. Results: The mean and standard deviation of the base surface temperature of bulk fill resin composite in groups I, II, and III, respectively, is 37.56 ± 1.06oC, group II 36.89 ± 1.23oC, and group III 36.00 ± 1.2 oC. It showed significantly different between the groups (p<0,05). Conclusion: The thicker the bulk fill resin composite, the lower the base surface temperature.

Surface roughness of supra-nano spherical filled and nanohybrid composite resin after Coffea arabica immersion: an experimental study

ABSTRACTIntroduction: Supra-nano spherical filled composite resin (Omnichroma, Tokuyama, Japan) with sol-gel method has 0.26 μm filler size, while nanohybrid composite resin (ENA HRi, Micerium, Italy) has 0.2-1 μm filler size. Nanofillers enhance resistance from chlorogenic acid contained in Coffea arabica. This study analyzed the surface roughness difference between supra-nano spherical-filled and nanohybrid composite resins after Coffea arabica immersion for 7 and 14 days, with 15 minutes of immersion each day. Methods: This study was an in vitro laboratory experiment with a pretest-posttest control group design. Twenty composite resin samples were immersed in artificial saliva and divided into four groups; supra-nano coffee, nanohybrid coffee, supra-nano saliva (control), and nanohybrid saliva (control). After 24 hours, immersion in Coffea arabica was started for supra-nano coffee group and nanohybrid coffee group for 15 minutes daily until days 7 and 14. Control groups were immersed in saliva. Results: One-way ANOVA showed significant differences in the surface roughness between composite resin groups. Post-hoc Tukey showed a significant difference between supra-nano coffee (0.91± 0.29 μm) and nanohybrid saliva (1.43±0.42 μm). The GLM Repeated Measure test showed significant surface roughness changes in supra-nano after 14 days of immersion in Coffea arabica (1.47±0.13 μm), while nanohybrid experienced surface roughness changes in 7 days of immersion in Coffea arabica (1.94±0.55 μm) and increased in 14 days (2.25±0.47 μm). In saliva immersion (control group), nanohybrid experienced an increase in surface roughness after 14 days, while supra-nano did not experience a significant increase in surface roughness. Conclusion: Supra-nano spherical filled composite resin exhibits greater resistance to changes in surface roughness following immersion in Coffea arabica.KEYWORDSCoffea arabica, nanohybrid, composite resin, supra-nano spherical filled, surface roughness

Does dental material type influence bacterial adhesion under the same polishing conditions? Direct observation using a fluorescent staining technique: An in vitro study.

Highly polished 3, 4, and 5 mol% yttria-stabilized zirconia and CAD/CAM composite resin samples were prepared, and the influence of surface roughness (Ra and Sa, 21 areas/group), wettability (contact angle and surface energy, 3 samples/group), and surface chemical composition (2 samples/group) on single-strain bacterial adhesion models (Porphyromonas gingivalis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus gordonii, and Streptococcus mutans) were compared via fluorescent staining with graphical analysis (21 areas/group). Statistical analysis was performed using the Shapiro-Wilk test followed by one-way analysis of variance with Tukey's test or the Kruskal-Wallis test with Dunn's test (α=0.05) and linear regression. For dental zirconia with the same surface roughness, the yttria content did not significantly influence the initial bacterial adhesion. However, higher bacterial adhesion was detected for the composite resin owing to its high C, O, and Si contents. There was no correlation between surface energy and bacterial adhesion for any bacterial strain (p<0.005).

An In Vitro Analysis of the Effects of Mouthwashes on the Surface Properties of Composite Resin Restorative Material.

Restorative composite resins have clinical prime importance in modern dental practice, but numerous factors influence their prognosis in the oral environment. Their interaction with oral care products, like mouthwashes, is one such factor. This study aimed to evaluate the quantifiable effects of different mouthwashes on the surface properties of the composite resin restorative material. The method involved formulating 90 samples of nanohybrid composite resins (Medicept Dental India Private Limited, Mumbai, India). The samples were treated with 1% alcohol, without alcohol, and with a saline solution (control). Surface roughness (Ra values) and microhardness had been checked before and after an exposure period of 24 hours. Data were thus tabulated, and from that, average values of surface roughness and microhardness were derived. This data was analyzed using the IBM SPSS Statistics for Windows, V. 26.0 (IBM Corp., Armonk, NY). Analysis of variance (ANOVA) and a t-test were used to compare the means of the variables. The level of significance was fixed at p < 0.05. The surface roughness value was significantly highest in the ethanol-containing mouthwash-treated samples after 24 hours of exposure (p < 0.05). The microhardness was statistically lower in these samples (p < 0.05). These research data give quantitative information, however, about the mass effect of mouthwashes on the composite resin restorative material. The presented changes, which were illustrated by the values of surface roughness and microhardness, are drawing attention to the fact that a cautious approach must be taken in the recommendations for oral care in the provision of intensive treatments with restorative composite resins.

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.

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

ObjectivesThe purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites. MethodsThe Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter. ResultsDirect contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range. SignificanceThe addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

The Effect Of Mouthwashes On Color Change In Universal Composite Resin

Background: The use of mouthwash has increased and become a habit since the Covid-19 pandemic. The use of mouthwash is recommended for prevention. The mouthwashes that American Dental Association (ADA) and Center for Disease Control and Prevention (CDC) recommended are chlorhexidine gluconate (CHX), hydrogen peroxide (H2O2), cetilpyridinium chloride (CPC), povidone iodine (PVP-I), dan chlorine dioxide (ClO₂). Universal composite resin is used for every tooth color requirement and has a chameleon effect that can disguise, eliminate, minimize, and neutralize mismatched colors. This study aims to determine various mouthwashes’ effects on the discoloration of universal composite resin. Method: This research is an experimental laboratory by comparing the color changes before and after treatment. Thirty samples of universal composite resin with a width of 10 mm and a height of 2 mm were divided into 5 mouthwash test groups and 1 control group. Color test using a Vita Easy Shade V spectrophotometer and the data were shown in DE assessment. Result: Data were analyzed with One Way ANOVA on DE assessment with the significance level p0.05 on 5 test groups. Conclusion: The 5 groups of mouthwashes showed there was a color change in the DE assessment of universal composite resin

Optimization Mechanism of Mechanical Properties of Basalt Fiber-Epoxy Resin Composites by Interfacially Enriched Distribution of Nano-Starch Crystals

Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength, designability, good dimensional stability and ease of large-area monolithic forming. However, the problem of interfacial bonding between the resin matrix and the fibres limits the direct use of reinforcing fibres and has become a central difficulty in the development of basalt fibre-epoxy composites. This paper proposes a solution for enhancing the strength of the fibre-resin interface using maize starch nanocrystals, which are highly yield and eco-friendly. Firstly, in this paper, corn starch nanocrystals (SNC) were prepared by hydrolysis, and were deposited on the surface of basalt fibers by electrostatic adsorption. After that, in order to maximize the modification effect of nano-starch crystals on the interface, the basalt fiber-epoxy resin composite samples were prepared by mixing in a pressureless molding method. The test results shown that the addition of basalt fibers alone led to a reduction in the strength of the sample. Deposition of 0.1 wt% SNC on the surface of basalt fibers can make the strength consistent with pure epoxy resin. When the adsorption amount of SNC reached 0.5 wt%, the tensile strength of the samples was 23.7% higher than that of pure epoxy resin. This is due to the formation of ether bond homopolymers between the SNC at the fibre-epoxy interface and the epoxy resin, which distorts the originally smooth interface, leading to increased stress concentration and the development of cracks. This enhances the binding of basalt fibers. The conclusions of this paper can provide an effective, simple, low-cost and non-polluting method of interfacial enhancement modification.

Effect of whitening toothpaste and toothpowder on nanofiller composite resin discoloration after immersion in black tea

Background: One of the factors of discoloration on composite resin is extrinsic factors, such as black tea. Various ways are used to restore the color of composite resin, for example, toothpaste or toothpowder with whitening ingredients. Adding whitening ingredients such as activated charcoal or pearl essence in toothpaste or toothpowder can remove pigments, chromophores, and stains on composite resin with an abrasion effect on the composite surface.Method: This research was an experimental laboratory with a pretest and post-test control group design. This study used 12 samples of nanofiller composite resin (Palfique LX5 B1) in a cylindrical shape with 10 mm diameter and 2 mm thickness. The research was conducted by immersing the samples in black tea for 4 hours with repetition for 13 days. After immersing, the samples were divided into 3 groups: group I was brushed with charcoal toothpaste, group II was brushed with whitening toothpowder, and group III was brushed with non-whitening toothpaste. Brushing was done for 3 minutes with repetition for 13 days. The color parameters were measured using VITA Easyshade V 3 times.Result: The Shapiro-Wilk normality test showed the data normally distributed (p&gt;0,05). The repeated ANOVA test showed no significant color change (p&gt;0,05).Conclusion: Charcoal toothpaste, whitening toothpowder, and non-whitening toothpaste affect the color change of nanofiller composite resin, but there is no significant color change between the three kinds of toothpaste.

The Effect of Charcoal-Based Dentifrice and Conventional Whitening Toothpaste on the Color Stability and Surface Roughness of Composite Resin: A Systematic Review of In Vitro Studies.

The objective was to systematically review studies that evaluated the effect of charcoal-based dentifrices (CbDs) and conventional whitening toothpastes (CWTs) on the color stability (CS) and/or surface roughness (SR) of composite resin (CR). The question we focused on was "Do CbD and CWT affect the CS and/or SR of CR?" Indexed databases were searched without language and time restrictions up to and including May 2023 using different keywords. Original experimental studies were included. The risk of bias (RoB) was assessed using the Quality Assessment Tool for In Vitro Studies. Ten in vitro studies performed on CR were included. The number of CR samples assessed ranged between 18 and 200. In one study, CbDs altered the CS and SR of CR, whereas another study showed no difference in changes in the SR and CS of CR when CbDs were compared with CWTs. One study showed that compared with CWTs, CbDs caused changes in the CS of CR but changes in SR were similar between the two dentifrices. One study showed that CbDs and CWTs improved the overall color and enhanced the SR of CR. Three studies had a high RoB, five had a medium RoB, and two had a low RoB. Compared to CWTs, CbDs appeared to affect the CS of CR, but the SR of CR induced by both dentifrices remained consistent. Further well-designed and power-adjusted studies are needed.

Influence of Thickness on the Translucency Parameter and Whiteness Index of Single-Shade Resin Composites.

The study aimed to evaluate the effect of thickness on the translucency parameter (TP) and whiteness index for dentistry (WID) of single-shade resin composites compared with a multi-shade resin composite after thermocycling. A total of 100 resin composite samples of five brands (Filtek Z250, Omnichroma, Vittra APS Unique, Zenchroma, and Charisma Diamond One) with thicknesses of 2 mm and 4 mm were prepared (n=10). CIE L*a*b* coordinates were obtained using a spectrophotometer. The resin composite samples were subjected to 10,000 thermocycles. Before and after thermocycling, TP values were calculated with the CIEDE2000 formula, and whiteness values were calculated using the WID. The influence of thickness, resin composite, and aging on these variables was analyzed using the generalized linear model (p<0.05). Omnichroma and Filtek Z250 exhibited, respectively, the highest and the lowest TP00 values compared with the other resin materials (p<0.001). The TP00 values of Zenchroma and Diamond One were similar (p>0.05). Vittra APS Unique had a lower TP than Zenchroma and Diamond One (p<0.001). Before thermocycling, the highest WID showed the combination of Vittra APS Unique with thicknesses of 2 mm (48.33±1.18). After thermocycling, the highest WID was shown in the combination of Vittra APS Unique with thicknesses of 2 mm (45.33±0.55) and 4 mm (46.23±0.94) (p<0.001). After thermocycling, the lowest WID was for the combination of Filtek Z250 with thicknesses 2 mm (21.16±0.93) and 4 mm (20.70±0.91) (p<0.001). The TP and WID values of the resin composites varied across different composites and thicknesses. Single-shade resin composites of different thicknesses demonstrated higher translucency and whiteness values than multi-shade resin composite, both before and after thermocycling.

Effects of Different Anti-Epileptic Drug Groups and Brushing on the Color Stability of Restorative Materials Used in Pedodontics: An In Vitro Evaluation.

This study will evaluate the effects of anti-epileptic drugs and brushing used in children on the color change of three restorative materials by creating an in vitro study model. Forty samples of polyacid-modified composite resin (compomer), glass ionomer cement (GIC), and composite resin (CR) were prepared. Samples were split into four groups (n = 10) and soaked in three anti-epileptic drugs (Tegretol, Depakine, Keppra) and distilled water. For each group (n = 5), two subgroups (brushing and non-brushing) were created. Discolorations [CIEDE2000 (ΔE00)] were determined initially and on days 7 and 14. The data were analyzed with a four-factor repeated measures ANOVA analysis, and a post hoc analysis Bonferroni test was used. After the second week, the highest ΔE00 value was seen in the non-brushed compomer material in the Tegretol drug group (8.59 ± 0.43). In contrast, the lowest value was seen in GIC filling material-brushing-Depakine drug (3.45 ± 2.14). ΔE00 values in the brushing groups were statistically significantly lower than those in the no brushing groups (p < 0.05). It has been determined that the color stability of aesthetic restorative dental materials used in pediatric dentistry is affected by antiepileptic drugs. In addition, it has been determined that tooth brushing positively affects the color stability of restorative materials. Therefore, pediatric dentists should advise their patients and their relatives about this issue and take precautions.

Assessment of surface roughness and compressive strength of resin-based composite using different types of bleaching protocols.

Background and objective: This study aimed to evaluate the effect of three types of bleaching protocols on the surface roughness and compressive strength of composite resin. Methods: Eighty composite resin samples were prepared using metal molds; forty samples (2 mm in height and 8 mm in diameter) for surface roughness evaluation and the other forty samples (6 mm in height and 4 mm in diameter) for compressive strength. Every forty samples were divided into four groups; Group 1 (n = 10) The samples were stored in deionized water at 37°C for two weeks as control, group 2 (n =10) The samples were subjected to bleaching with 22% Carbamide Peroxide (CP) Home bleaching, group 3 (n =10) The samples were subjected to bleaching with 14% Hydrogen Peroxide (HP) Home bleaching and group 4 (n =10) The samples were subjected to bleaching with 25% Hydrogen Peroxide (HP in-Office) in a dental clinic. After bleaching, groups 2, 3, and 4 were evaluated for surface roughness and compressive strength. Results: The enamel surface roughness of all specimens were increased after bleaching protocols to a very similar extent with no statistically significant difference between the means of enamel roughness of the control group and the other three groups and the highest value was recorded in the Carbamide Peroxide group (CP), while compressive strength of the composite was decreased after using bleaching protocols in all groups in comparison with the control group and the least compressive strength was recorded in (HP) group followed by (HP in-Office) group and (CP) group respectively. Conclusions: Within the limitation of this study, the following conclusions can be drawn: There was a decrease in surface roughness using different types of bleaching protocols (22% CP and 14% HP) at-Home bleaching technique and (25%) in-Office HP bleaching. Although there was no significant difference between them. The compressive strength of the composite resin was reduced after bleaching with no significant difference. Keywords: Bleaching protocol, Hydrogen peroxide, Carbamide peroxide

THow the Translucency and Color Stability of Single-Shade Universal Resin Composites Are Affected by Coffee?

Objective: The aim of this study was to examine how staining with coffee affects single-shade universal resin composites and a multi shade universal resin composite in terms of translucency and color stability. Method: Five different resin composites (Omnichroma, Vittra APS Unique, Zenchroma, Charisma Diamond One, and Neo Spectra ST) were used to create 50 samples (n=10). A spectrophotometer was used to record translucency parameter (TP00) and color changes ( ΔE00) at baseline and after immersion in coffee for 24 h. Color differences were calculated according to CIEDE2000. Data analysis was performed using one-way ANOVA and the paired-samples t-test. Results: After immersion of resin composite samples in coffee for 24 h the Vittra APS Unique group showed the highest ΔE00 value and the Neo Spectra ST group the lowest (P

A graphene@Cu-MOF hybrid synthesized by mechanical ball milling method and its flame retardancy and smoke suppression effect on EP

The traditional method of preparing graphene will cause serious environmental pollution, and the combustion of polymer materials will seriously harm people's health. In this paper, a Cu-MOF-coated graphene composite flame retardant (G@Cu-MOF) rich in flame retardant elements such as B and N was synthesized through green mechanical ball milling method. Flame retardants reduce the threat to the environment and people's lives and property. After adding 6 wt% G@Cu-MOF, the peak heat release rate, total heat release rate, CO production and CO2 production of epoxy resin (EP) composite samples decreased by 55, 14, 59, and 55%, respectively. This type of Cu-MOF releases incombustible gases such as boron trifluoride (BF3) and ammonia (NH3) during combustion, diluting the concentration of combustible gases and producing copper borate in the condensed phase. Cu2+ is reduced to Cu, and boron compounds are converted into boron oxides. The thermal conductivity of graphene can reduce the temperature of the matrix, and has good flame retardancy. It synergistically acts with Cu-MOF to promote the formation of high-quality residual char, and can significantly inhibit the heat and smoke release of EP. It plays a role in flame retardancy and protecting the substrate from fire. This study provides a new approach for preparing graphene hybrid flame retardants through mechanical ball milling, in order to improve the flame retardancy of EP and suppress the release of smoke and toxic gases.

Bacterial adhesion to composite resins produced by additive and subtractive manufacturing.

The aim of this study was to evaluate the surface roughness and contact angle of composite resins produced by CAD/CAM milling and three-dimensional (3D) printing for permanent restorations as well as the adhesion of S. mutans and S. sanguinis bacteria to these composites. Three CAD/CAM milling composite resins (Vita Enamic-VE, Cerasmart-CE, Lava Ultimate-LU) and three 3D printing resins (Varseo Smile Crown plus-VSC, Saremco print Crowntech-SPC, Formlabs 3B Permanent crown-FLP) were selected. Twenty samples were prepared for each group. Using a contact profilometer, the surface roughness was determined, and an optical goniometer was used to quantify the contact angle. To evaluate the bacterial adhesion, composite specimens were immersed in mucin containing artificial saliva. All samples were incubated for 24h at 37°C in 5% CO2. CFUs were determined by counting colonies after the incubation period. Surface roughness values of test samples were the highest in the Group VSC [0.46 (0.14)µm], whereas the lowest values were found in the Group LU [0.23 (0.05)µm]. There was no statistically significant difference between the groups in contact angle values (p > 0.05). The S. mutans adhesion extent on the Group SPC was statistically higher compared to all other materials with p < 0.05. For S. sanguinis, the lowest bacterial adhesion value was recorded in Group CE (3.00 × 104CFU/ml) and statistically significant differences were found with Group VE and VSC (p < 0.05). Different digital manufacturing techniques and material compositions can affect the surface roughnesses of composite resins. All composite resin samples have hydrophobic characteristics. Microbial adhesion of the tested composite resins may be varied depending on the bacterial species. S. mutans showed much more adhesion to these materials than S. sanguinis.