Experimental Resin Composites Research Articles

Light curing and ratio of glass/fumed silica fillers on degree of conversion and mechanical properties of experimental composite resins

ABSTRACTThis study evaluated the degree of conversion and mechanical properties of experimental composite resins made with different fillers and light‐curing methods. All composites had the same organic matrix (40% wt) and photoinitiator system (1.2% wt). Experimental composite groups were divided according to ratio (%) of silanated ground glass (0.5 μm) (BaAlSi) and fumed silica (SiO2): 100/0, 90/10, 80/20, and 70/30. Light‐emitting diode light was used in the continuous, soft‐start, and pulse‐delay modes (n = 10). Degree of conversion was determined using attenuated total reflectance–Fourier transform infrared spectroscopy. Flexural strength and modulus were obtained using a universal testing machine, and Knoop microhardness was measured in a Knoop indenter. The data were subjected to a two‐way ANOVA and Tukey's post hoc test (α = 0.05). Continuous‐light exposure of the 100/0 group produced the highest degrees of conversion. Soft‐start exposure of the 70/30 groups produced the highest Knoop microhardness. The pulse‐delay method produced the lowest flexural strength and modulus values. The 100/0 and 70/30 groups had the lowest flexural strength and flexural modulus, respectively. Application of continuous‐light output with composite resins containing a ratio of 80/20 (BaAlSi/SiO2) fillers generated the best results regarding the degree of conversion and mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47008.

Effect of Incorporation of Self-Healing Microcapsules to Experimental Resin Composite on Some Mechanical Properties

Purpose: The present study aimed to investigate the effect of incorporation of the new Triethylene glycoldimethacrylate and N,N-Bis(2-hydroxyethyl)-p-toluidine (TEGDMA)- (DHEPT) in polyurea formaldehyde (PUF) micro-capsules into an experimental dental resin composite on the flexural strength and fracture toughness and the evaluation of its self- healing efficacy. Materials and Methods: Polyurea formaldehyde microcapsules were synthesized by insitu polymerization technique, encapsulating a triethylene glycol dimethacrylate and dihydroxy ethyl para toluidine (TEGDMA–DHEPT) as a healing liquid, then experimental composite resin is prepared. Microcapsules are incorporated in the resin composite with concentrations 0%, 2.5%, 5%, 7.5% and 10%, then experimental resin composite specimens were fabricated. Fracture toughness and flexural strength were examined by three point loading using universal testing machine till fracture. The fracture toughness was evaluated by using single edge V-notched beam method, self healing efficacy is evaluated as the ratio between the healed fracture toughness and the virgin fracture toughness. Results: Regarding flexural strength results, it was found that the 0% group has the highest flexural strength while the 10% group had the lowest flexural strength. On the other hand, on evaluating the results, of 7.5% group it was found that this concentration did not affect the flexural strength remarkably. Regarding the virgin fracture toughness results, 0% group has the highest flexural strength, while the 10% group the lowest flexural strength, specimens were fractured and healed, then fractured again to measure the healed fracture toughness, on examining the results of the healed fracture toughness, it was found that no significant difference between 0% and 2.5% as no healing occur at such specimen, Also the results showed that the highest healed fracture toughness was in 5%, followed by 7.5%, followed by 10%. The self-healing efficacy increased to a recovery of about 75% in KIC when the microcapsule mass fraction was increased from 5% to 7.5% till reaching 10% concentration. Conclusions: In light of restoration fracture as one of the primary failure reasons, the novel self-healing dental composite may be promising to heal crack damages and to prolong the durability of the restoration clinically.

Real-time curing characteristics of experimental resin composites containing amorphous calcium phosphate.

The real-time polymerization of light-curable experimental resin composites filled with amorphous calcium phosphate (ACP) was monitored. Experimental composites were based on a 2,2-bis[4-(2-ethoxy-3-methacryloyloxy propoxy)phenyl]propane (Bis-EMA)/triethyleneglycol dimethacrylate (TEGDMA)/2-hydroxyethyl methacrylate (HEMA) resin photoactivated by a camphorquinone/tertiary amine system. Four ACP composites were prepared, containing 40 wt% ACP and 0/10 wt% reinforcing fillers (barium glass and silica). Additionally, two control composites were prepared which contained only reinforcing fillers (40-50 wt%). The degree of conversion (DC) was monitored in real time using a Fourier-transform infrared (FTIR) spectrometer with an attenuated total reflectance accessory. During the light curing (1,219 mW cm-2 ) for either 20 or 40 s, infrared spectra were collected from the bottom of 2-mm-thick composite specimens at the rate of two spectra per second over 5 min. When cured for 40 s, the ACP composites attained a high DC (89.1%-92.4%), while the DC of control composites was significantly lower (53.5%-68.4%). All materials showed a lower DC for the shorter curing time (20 s) and various extents of 5-min postcure polymerization: 12.9%-21.5% for the ACP composites and 2.7%-5.2% for the control composites. The control composites reached the maximum reaction rate much earlier (4.1-4.3 s) and at lower DC (9.9%-10.4%) than did the ACP composites (17.4-22.0 s and 43.5%-49.3%, respectively).

Polymerization kinetics of experimental bioactive composites containing bioactive glass

ObjectivesTo investigate the polymerization kinetics and the degree of conversion (DC) of experimental resin composites with varying amount of bioactive glass 45S5 (BG). MethodsExperimental resin composites based on a photo-curable Bis-GMA/TEGDMA resin system were prepared. The composite series contained 0, 5, 10, 20, and 40 wt% of BG and reinforcing fillers up to the total filler amount of 70 wt%. Composite specimens were light cured with 1219 mW/cm2 for 20 or 40 s and their DC was monitored during 5 min at the data collection rate of 2 s−1 using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). ResultsThe 5-min DC values for experimental composites were in the range of 42.4–55.9% and 47.3–57.9% for curing times of 20 and 40 s, respectively. The differences in the 5-min DC between curing times of 20 s or 40 s became more pronounced in materials with higher BG amount. Within both curing times, a decreasing trend of the 5-min DC values was observed with the increasing percentage of BG fillers. The maximum polymerization rate also decreased consistently with the increasing BG amount. ConclusionsUnsilanized BG fillers showed a dose-dependent inhibitory effect on polymerization rate and the DC. Extending the curing time from 20 to 40 s showed a limited potential to improve the DC of composites with higher BG amount. SignificanceThe observed inhibitory effect of BG fillers on the polymerization of resin composites may have a negative influence on mechanical properties and biocompatibility.

Curing potential of experimental resin composites with systematically varying amount of bioactive glass: Degree of conversion, light transmittance and depth of cure

ObjectivesThe aim of this work was to investigate the curing potential of an experimental resin composite series with the systematically varying amount of bioactive glass 45S5 by evaluating the degree of conversion, light transmittance and depth of cure. MethodsResin composites based on a Bis-GMA/TEGDMA resin with a total filler load of 70 wt% and a variable amount of bioactive glass (0–40 wt%) were prepared. The photoinitiator system was camphorquinone and ethyl-4-(dimethylamino) benzoate. The degree of conversion and light transmittance were measured by Raman spectroscopy and UV–vis spectroscopy, respectively. The depth of cure was evaluated according to the classical ISO 4049 test. ResultsThe initial introduction of bioactive glass into the experimental series diminished the light transmittance while the further increase in the bioactive glass amount up to 40 wt% caused minor variations with no clear trend. The curing potential of the experimental composites was similar to or better than that of commercial resin composites. However, unsilanized bioactive glass fillers demonstrated the tendency to diminish both the maximum attainable conversion and the curing efficiency at depth. ConclusionsExperimental composite materials containing bioactive glass showed a clinically acceptable degree of conversion and depth of cure. The degree of conversion and depth of cure were diminished by bioactive glass fillers in a dose-dependent manner, although light transmittance was similar among all of the experimental composites containing 5–40 wt% of bioactive glass. Clinical significanceReduced curing potential caused by the bioactive glass has possible consequences on mechanical properties and biocompatibility.

The antibacterial, cytotoxic, and flexural properties of a composite resin containing a quaternary ammonium monomer

Statement of problemThe use of composite resin to restore teeth has increased substantially during the last decades. However, secondary caries and the fracture of restorations are the leading reasons for clinical restoration failure. Mechanically strong composite resins with caries-inhibition capabilities are needed. Although antibacterial dimethacrylate quaternary ammonium monomers have been synthesized, composite resin containing dimethacrylate quaternary ammonium monomers and glass fillers has rarely been reported. PurposeThe purpose of this in vitro study was to evaluate the possibility of the clinical use of an experimental composite resin containing urethane dimethacrylate quaternary ammonium compound (UDMQA-12) by investigating its antibacterial activity, cytotoxicity, flexural strength, and flexural modulus. Material and methodsAntibacterial activity against Streptococcus mutans was investigated by means of direct contact test. The antibacterial activity of specimens after water immersion and saliva treatment was also tested. These were compared with a commercially available composite resin, Z250, and a glass ionomer cement, Fuji VII. Effects of the eluent from the experimental composite resin on the metabolic activity of human dental pulp cells were quantified. Disks of 1 mm in thickness and 15 mm in diameter were used in the antibacterial and cytotoxic tests. Flexural strength and flexural modulus were measured with a 3-point bend test with bars of 2×2×25 mm. Three commercially available composite resins (Filtek Z250, G-aenial Anterior, and G-aenial Posterior) were used as controls in the flexural test. ResultsBacterial growth was inhibited on the experimental composite resin. After water immersion or saliva treatment, the experimental composite resin showed significant antibacterial effect compared with the conventional composite resin (P<.05). No significant difference was found in cytotoxicity between the experimental composite resin and the conventional composite resin (P＞.05), and a significantly higher cytotoxicity was shown by glass ionomer cement compared with the experimental composite resin and the conventional composite resin (P<.05). The conventional composite resin had the highest flexural strength and flexural modulus (P<.05), followed by the experimental composite resin, then G-ænial Posterior and G-ænial Anterior. ConclusionsThe antibacterial experimental composite resin was biocompatible and had mechanical properties similar to those of some commercially available composite resins. It might, therefore, be useful in preventing the occurrence of secondary caries.

Macro- and microtopographical examination and quantification of CAD-CAM composite resin 2- and 3-body wear

Statement of problemThe selection of an appropriate restorative material based on wear behavior is important for the long-term success of a dental restoration. For computer-aided design and computer-aided manufacturing (CAD-CAM) composite resins, information about their wear resistance and wear mechanism is scarce. PurposeThe purpose of this in vitro study was to compare the 2- and 3-body wear of CAD-CAM composite resins with that of lithium disilicate ceramic and to develop analysis software. Material and methodsFlat specimens were prepared from the following CAD-CAM composite resins: Cerasmart (CS), SHOFU Block HC (SH), Katana Avencia (KA), Brilliant Crios (BC), an experimental composite resin (EXP), and lithium disilicate ceramic IPS e.max CAD (REF). The specimens underwent 2-body wear (50 N, 5/55°C, 400 000 cycles) opposed by human enamel antagonists. Specimen wheels were prepared with each material on each wheel for 3-body wear with a millet slurry (15 N, 15% slip, 200 000 cycles). All specimens were digitized by using a dedicated laser scanner. Analysis software was developed to calculate macrotopographical examination of volume loss. The microtopography of the surfaces was examined by using scanning electron microscopy. For data analysis, the Kruskal-Wallis test with the Tukey-Kramer post hoc test and the 1-sample Wilcoxon test were used (α=.05). ResultsAfter 2-body wear simulation, SH and KA presented higher volume loss than the other CAD-CAM materials. For 3-body wear, REF had lower volume loss than CS, SH, or BC. In addition, BC led to higher volume loss than EXP. The patterns of 2- and 3-body wear were different. ConclusionsThe ceramic showed good global wear resistance. The volume loss of the CAD-CAM composite resins differed and depended on the material. The 2- and 3-body wear test methods tended to differ with regard to volume loss. Examination of the worn surfaces revealed different mechanisms acting in 2- and 3-body wear test.

A novel Triclosan Methacrylate-based composite reduces the virulence of Streptococcus mutans biofilm.

The use of antimicrobial monomers, linked to the polymer chain of resin composites, is an interesting approach to circumvent the effects of bacteria on the dental and material surfaces. In addition, it can likely reduce the incidence of recurrent caries lesions. The aim of this study was to evaluate the effects of a novel Triclosan Methacrylate (TM) monomer, which was developed and incorporated into an experimental resin composite, on Streptococcus mutans (S. mutans) biofilms, focusing on the analyses of vicR, gtfD, gtfC, covR, and gbpB gene expression, cell viability and biofilm characteristics. The contact time between TM-composite and S. mutans down-regulated the gbpB and covR and up-regulated the gtfC gene expression, reduced cell viability and significantly decreased parameters of the structure and characteristics of S. mutans biofilm virulence. The presence of Triclosan Methacrylate monomer causes harmful effects at molecular and cellular levels in S. mutans, implying a reduction in the virulence of those microorganisms.

HPLC analysis of eluted monomers released from dental composites containing bioactive glass

Objectives: The aim of the present study is to evaluate the released residual monomers from composite resins that contain different proportions of bioactive glass (BAG). Methods: Experimental resin composites were prepared by a resin matrix (50% BisGMA and 50% TEGDMA) and inorganic filler with BAG (5, 10 and 30%). Each resin composite was placed in the tooth cavity (n = 5). After polymerisation, samples were immediately immersed in 75% ethanol and 25% deionised water (6 ml) at 37 °C. Residual monomers (Bis-GMA, TEGDMA, HEMA and UDMA) that were eluted from the composites for 10 m, 1 h, 1 d, 7 d and 30 d were analysed by high-performance liquid chromatography (HPLC). The data were analysed with one-way ANOVA and Tukey HSD at a p < 0.05 significance level. Results: Among the time periods, the fastest released residual monomer was observed in the 10 m elution. The highest amount of released residual monomer from all groups (except the control group) was TEGDMA, whereas this was HEMA for the control group. The amounts of residual monomers eluted from BAG30 were significantly higher than other groups (p < 0.05). Conclusions: The release of the monomer increases in accordance with the increased BAG addition to the composite resins.

Effect of low-shrinkage monomers on the physicochemical properties of experimental composite resin

This study was conducted to determine whether novel experimental low-shrinkage dimethacrylate co-monomers could provide low polymerization shrinkage composites without sacrifice to degree of conversion, and mechanical properties of the composites. Experimental composites were prepared by mixing 28.6 wt% of bisphenol-A-glycidyl dimethacrylate based resin matrix (bis-GMA) with various weight-fractions of co-monomers; tricyclo decanedimethanol dacrylate (SR833s) and isobornyl acrylate (IBOA) to 71.4 wt% of particulate-fillers. A composite based on bis-GMA/TEGDMA (triethylene glycol dimethacrylate) was used as a control. Fracture toughness and flexural strength were determined for each experimental material following international standards. Degree of monomer-conversion (DC%) was determined by FTIR spectrometry. The volumetric shrinkage in percent was calculated as a buoyancy change in distilled water by means of the Archimedes’ principle. Polymerization shrinkage-strain and -stress of the specimens were measured using the strain-gage technique and tensilometer, respectively with respect to time. Statistical analysis revealed that control group had the highest double-bond conversion (p < .05) among the experimental resins tested. All of the experimental composite resins had comparable flexural strength, modulus, and fracture toughness (p > .05). Volumetric shrinkage and shrinkage stress decreased with increasing IBOA concentration. Replacing TEGDMA with SR833s and IBOA can decrease the volumetric shrinkage, shrinkage strain, and shrinkage stress of composite resins without affecting the mechanical properties. However, the degree of conversion was also decreased.

Inhibitory effect of resin composite containing S-PRG filler on Streptococcus mutans glucose metabolism

ObjectivesResin composites containing surface pre-reacted glass-ionomer (S-PRG) fillers have been reported to inhibit Streptococcus mutans growth on their surfaces, and their inhibitory effects were attributed to BO33− and F− ions. The aim of this study was to evaluate S. mutans acid production through glucose metabolism on resin composite containing S-PRG fillers and assess inhibitory effects of BO33− and F− on S. mutans metabolic activities. MethodsThe pH change through S. mutans acid production on experimental resin composite was periodically measured after the addition of glucose. Inhibitory effects of BO33− or F− solutions on S. mutans metabolism were evaluated by XTT assays and measurement of the acid production rate. ResultsThe pH of experimental resin containing S-PRG fillers was significantly higher than that of control resin containing silica fillers (p < 0.05). OD450 values by XTT assays and S. mutans acid production rates significantly decreased in the presence of BO33− and F− compared with the absence of these ions (p < 0.05). ConclusionspH reduction by S. mutans acid production was inhibited on resin composite containing S-PRG fillers. Moreover, S. mutans glucose metabolism and acid production were inhibited in the presence of low concentrations of BO33− or F−. Clinical significanceBO33− or F− released from resin composite containing S-PRG fillers exhibits inhibitory effects on S. mutans metabolism at concentrations lower than those which inhibit bacterial growth.

Effect of the Bis-Dimethylamino Benzydrol Coinitiator on the Mechanical and Biological Properties of a Composite.

To examine the effect of the alternative coinitiator 4,4'bis dimethylamino benzydrol (BZN) in degree of conversion (DC), mechanical and biological properties of experimental composites. The coinitiator BZN was used in three concentrations (0.2, 0.5 and 1.2%), and the coinitiator DMAEMA was used as control at the same concentrations as above. The molar concentration of camphorquinone (CQ) and coinitiators was kept constant (1:1). The composites were manipulated and submitted to microhardness test (VHN), flexural and compressive strength (in MPa), elastic modulus (GPa), DC (FT-IR) and in vitro cytotoxicity (against 3T3 fibroblastic cells) of the experimental resins. Data were subjected to two-way ANOVA and Tukey post-test (α=0.05). The experimental composite resin with BZN showed higher DC values compared to control DMAEMA groups. For the mechanical properties, microhardness values were higher in BZN groups; flexural strength and elastic modulus were similar between all the groups. Compressive strength for groups BZN0.5 and DMAEMA0.5 were not statistically different, being the lowest values attributed to group BZN0.2. The experimental resins with BZN and DMAEMA were considered nontoxic against 3T3 fibroblasts. The inclusion of the coinitiator BZN in experimental composites was considered nontoxic against 3T3 fibroblast cells, without compromising DC and mechanical properties.

Influence of Different Concentration and Ratio of a Photoinitiator System on the Properties of Experimental Resin Composites.

The aim in this study was to evaluate the influence of different ratio of camphorquinone/tertiary amine concentration on the flexural strength (FS), elastic modulus (EM), degree of conversion (DC), yellowing (YL), water sorption (WS) and water solubility (WSL) of experimental composites. Thus, acrylate blends were prepared with different camphorquinone (CQ) and amine (DABE) concentrations and ratios by weight: (CQ/DABE%): 0.4/0.4% (C1), 0.4/0.8% (C2), 0.6/0.6% (C3), 0.6/1.2% (C4), 0.8/0.8% (C5), 0.8/1.6% (C6), 1.0/1.0% (C7), 1.0/2.0% (C8), 1.5/1.5% (C9), 1.5/3.0% (C10). For the FS and EM, rectangular specimens (7x2x1 mm, n=10) were photo-activated by single-peak LED for 20 s and tested at Instron (0.5 mm/min). Then, the same specimens were evaluated by FTIR for DC measurement. For YL, disks (5x2 mm, n=10) were prepared, light-cured for 20 s and evaluated in spectrophotometer using the b aspect of the CIEL*a*b* system. For WS and WSL, the volume of the samples was calculated (mm³). For WS and WSL, composites disks (5x0.5 mm, n=5) were prepared. After desiccation, the specimens were stored in distilled water for 7 days and again desiccated, in order to measure the WS and WSL. Data were submitted to one-way ANOVA and Tukey's test (5%). The groups C8, C9 and C10 showed higher DC, EM and YL means, compared to other composites. Therefore, the FS and WS values were similar among all groups. Also, C1, C2 and C3 presented higher WSL in 7 days, compared to other composites. In general, higher concentrations of camphorquinone promoted higher physical-mechanical properties; however, inducing higher yellowing effect for the experimental composites.

Effectiveness of the DHMAI monomer in the development of an antibacterial dental composite

ObjectiveDevelopment of antibacterial dental composites is the ultimate goal to decrease carious disease occurrence and increase the restoration longevity. For this purpose, the quaternary ammonium dimethyl-hexadecyl-methacryloxyethyl-ammonium iodide (DHMAI) and the methacryloyloxyethylphosphorylcholine (MPC) have been incorporated in experimental methacrylate-based composite resins. This aims to first investigate the effect of each alone and then their combined effect. MethodsSynthesized DHMAI and commercial MPC were added either alone or combined at different concentrations to experimental dental composite. Flexural strength (FS) and modulus (FM) were tested to select the optimal concentrations. Only selected composites were evaluated for Vickers hardness (HV) and the degree of conversion (DC) using fourier transform infrared spectroscopy analysis (FTIR-ATR). Antibacterial activity was assessed using tests on colony-forming unit (CFU), scanning electron microscopy (SEM) and Alamarblue assay to measure the metabolic activity. Streptococcus mutans biofilm was chosen to be grown on the composite surfaces during 96h at 37°C. ResultsIncorporation of 7.5% DHMAI in composite improved the degree of conversion and gave a strong antibacterial effect with a reduction of (∼98%) in CFU and (∼50%) of metabolic activity with acceptable mechanical properties. Addition of MPC to DHMAI affects mechanical properties of composites without providing a better antibacterial activity. SignificanceComposites with DHMAI greatly reduced S. mutans biofilm and improved the degree of conversion without scarifying the composites’ mechanical properties. DHMAI may have wide applicability to other dental materials in order to inhibit caries and improve the longevity of restorations.

The effects of different opacifiers on the translucency of experimental dental composite resins

ObjectiveThe aim of this study was to evaluate the effects of different opacifiers on the translucency of experimental dental composite-resins. MethodsThree metal oxides that are used as opacifiers were tested in this study: titanium oxide (TiO2), aluminium oxide (Al2O3) and zirconium oxide (ZrO2). Experimental composite-resins were fabricated containing 25wt.% urethane dimethacrylate (UDMA)-based resin matrix and 75% total filler including different concentrations of metal oxides (0, 0.25, 0.5, 0.75 and 1wt.%) blended into silane treated barium-silicate filler. The specimens (15.5mm diameter and 1mm thickness) were light-cured and tested in the transmittance mode using a UV/VIS spectrophotometer at wavelengths from 380 to 700nm under a standard illuminant D65. The color differences (ΔE* ab) between different concentrations of opacifiers were also measured in transmittance mode based on their Lab values. ResultsStatistical analysis by ANOVA and Tukey’s test showed a significant decrease (p<0.05) in light transmittance with the addition of opacifiers to the experimental composite-resins. There was a linear correlation between different concentrations of TiO2 and Al2O3 and total transmittance. Total transmittance was also found to be wavelength dependent. The color differences for the concentrations of 0–1wt.% of the opacifiers were above 1 ΔE* unit, with Al2O3 showing the smallest color shift. SignificanceThe type and the amount of the opacifiers used in this study had a significant effect on the translucency of the experimental UDMA-based dental composite resins. The most effective opacifier was TiO2, followed by ZrO2 and Al2O3 in decreasing order, respectively.

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.

Cytotoxicity of Experimental Resin Composites on Mesenchymal Stem Cells Isolated from Two Oral Sources.

Resin composite materials that are used to restore tooth cervical lesions associated with gingival recessions can hamper healing after root coverage surgeries. This study evaluates the in vitro cytotoxic effect of five resin composites (two commercial and three experimental) on oral mesenchymal stem cells (MSCs) and the persistence of stemness properties in high passage MSCs. Sorption and solubility tests were made for all materials. MSCs were isolated from re-entry palatal and periodontal granulation tissues and were characterized and cultured on composite discs. Cytotoxicity of the materials was evaluated by the Alamar Blue viability test, by Paul Karl Horan (PKH) labeling, and by immunocytochemical staining for actin. Water and saliva sorption and solubility data revealed that two of the experimental materials behaved comparable with the marketed resin composites. The Alamar Blue viability test shows that both cell lines grew well on composite discs that seemed to induce no apparent toxic effects. No signs of disruption of cytoskeleton organization was seen. Experimental resin composites can be recommended for further investigation for obtaining approval for use. The standard minimal criteria were fulfilled for high passage MSCs. Palatal tissue regains its regenerative properties in terms of MSC presence in the re-entry area after 6 months of healing.

Antibacterial activity of resin composites containing surface pre-reacted glass-ionomer (S-PRG) filler

ObjectiveA surface pre-reacted glass-ionomer (S-PRG) filler is a technology of interest for providing bio-functions to restorative materials. Resin composites containing S-PRG filler have been reported to show less plaque accumulation and reduced bacterial attachment. In this study, experimental resin composites containing S-PRG filler at various concentrations were fabricated, and the inhibitory effects on bacterial growth on their surface and the association of ions released from S-PRG filler with antibacterial activity were evaluated. MethodsFive kinds of experimental resin composites containing S-PRG filler at 0, 13.9, 27.3, 41.8, or 55.9 (vol.%) were fabricated. Streptococcus mutans was cultured on the cured discs for 18h to examine the growth of bacteria in contact with the surface of the experimental resins. The concentrations of Al3+, BO33−, F−, Na+, SiO32−, or Sr2+ released from each experimental resin into water were measured. The standardized solutions of each ion were prepared at the concentrations determined to be released from the experimental resin, and their inhibitory effects of single ion species on S. mutans growth were evaluated by using each standardized solution. ResultsResin composites containing S-PRG filler at 13.9 (vol.%) or greater inhibited S. mutans growth on their surface. When S. mutans was incubated in the presence of six kinds of ions at the concentrations released from the resin composite containing S-PRG filler at 55.9 (vol.%), a significant reduction in bacterial number was observed for BO33−, F−, Al3+, and SiO32−. Among these four ions, BO33− and F− demonstrated the strongest inhibitory effect on S. mutans growth. SignificanceOur findings suggest that resin composites containing S-PRG filler inhibit the growth of S. mutans on their surface. BO33−, F−, Al3+ and SiO32− released from S-PRG filler have the ability to inhibit S. mutans growth, and the inhibitory effects are mainly attributed to release of BO33− and F−.

Antimicrobial and mechanical properties of dental resin composite containing bioactive glass.

The aim of this study was to evaluate the antimicrobial efficacy and mechanical properties of dental resin composites containing different amounts of microparticulate bioactive glass (BAG). Experimental resin composites were prepared by mixing resin matrix (70% BisGMA and 30% TEGDMA) and inorganic filler with various fractions of BAG to achieve final BAG concentrations of 5, 10 and 30 wt%. Antimicrobial efficacy was assessed in aqueous suspension against Escherichia coli, Staphylococcus aureus and Streptococcus mutans and in biofilm against S. mutans. The effect of incorporation of BAG on the mechanical properties of resin composite was evaluated by measuring the surface roughness, compressive strength and flexural strength. Under the dynamic contact condition, viable counts of E. coli, S. aureus and S. mutans in suspensions were reduced up to 78%, 57% and 50%, respectively, after 90 minutes of exposure to disc-shaped composite specimens, depending on the BAG contents. In 2-day-old S. mutans biofilm, incorporation of BAG into composite at ratios of 10% and 30% resulted in 0.8 and 1.4 log reductions in the viable cell counts compared with the BAG-free composite, respectively. The surface roughness values of composite specimens did not show any significant difference (p&gt;0.05) at any concentration of BAG. However, compressive and flexural strengths of composite were decreased significantly with addition of 30% BAG (p&lt;0.05). The results demonstrated the successful utilization of BAG as a promising biomaterial in resin composites to provide antimicrobial function.

Stability of initiation systems in acidic photopolymerizable dental material

ObjectivesThis study simulated the shelf life to evaluate the stability of initiation systems on acidic photopolymerizable dental material, through an experimental self-adhering flowable composite resin (SACR). MethodsAn SACR model was formulated with monomers Bis-GMA, TEGDMA, acidic monomer (GDMA-P), and inorganic fillers. Initiation system combinations of camphorquinone (CQ), tertiary amine (EDAB), diphenyl phosphine oxide (TPO), phenylbis phosphine oxide (BAPO), and the diphenyliodonium hexafluorophosphate (DPIHFP) were tested. Five SACRs were evaluated, varying the initiation system: SACRCQ, SACRCQ+EDAB, SACRCQ+EDAB+DPIHFP, SACRBAPO and SACRTPO. The SARC were stored at 23°C and, according to shelf life, were evaluated for degree of conversion (DC), polymerization rate (Rp) and microtensile bond strength (μTBS). The DC was evaluated after 0, 1, 2, 4, 8, 12, 24 and 48 storage weeks of SACRs. Bonding to dentin was performed after 0, 4, 8, 12 and 24 storage weeks of SACRs and tested immediately (24h) and after 6 and 12 months by μTBS. Halogen light curing unit (3M ESPE) was used for photoactivation procedures. ResultsSACRCQ+EDAB+DPIHFP showed higher Rp. The DC of SACRCQ+EDAB, SACRCQ+EDAB+DPIHFP, and SACRBAPO were similar (40%) and higher than SACRTPO and SACRCQ (20 and 10%, respectively), staying stable up to 48 weeks. The SACRCQ, SACRCQ+EDAB, and SACRTPO had pre-testing failure on μTBS. The shelf life of SACRs did not affect the μTBS of the groups that obtained adhesion. Furthermore, the immediate μTBS (MPa) SACRCQ+EDAB+DPIHFP (8.4) was similar to SACRBAPO (10.5); however, after 12 months, only SACRCQ+EDAB+DPIHFP maintained the μTBS. SignificanceThe choice of a suitable initiation system is crucial to the performance and stability of acidic photopolymerizable dental material.