Vickers microhardness comparison of 4 composite resins with different types of filler

A Comparative Evaluation of Surface Properties of Cention N and TiO2-Enriched Cention N After Brushing Simulation and Erosive Challenge: An In Vitro Study

Background This study aimed to evaluate and compare the abrasive and erosive wear resistance of Cention N and titanium dioxide (TiO2) nanoparticle-enriched Cention N after three years of brushing simulation. Methodology A total of 48 freshly extracted mandibular molars were mounted in acrylic blocks and divided into two groups of 24 molars based on the type of restorative material used to restore them. Cavities of a standardized size were prepared. Group A was restored with Cention N, and group B was restored with 5% TiO2-enriched Cention N. Each group was further divided into three subgroups of eight. Subgroup 1 was the control subgroup. Subgroup 2 was the abrasive subgroup, subjected to the abrasive challenge in a brushing stimulator with 30,000 cycles to 10,000 cycles in the linear X-axis and Y-axis each and another 10,000 cycles divided into 5,000 cycles clockwise and 5,000 cycles anticlockwise. The total number of brushing cycles was equal to three years of brushing with a duration of eight to nine hours. Subgroup 3 was the erosive and abrasive subgroup, subjected to an erosive pH cycle consisting of exposure to Coca‑Cola for five minutes thrice a day for seven days, and then subjected to brushing simulation as above. After the surface treatment, specimens were subjected to the Vickers microhardness test using a diamond indenter and the surface roughness test using an optical profilometer. The resulting values were subjected to statistical analysis. Results There was a significant decrease in mean surface roughness in group B, where TiO2 nanoparticles were added after erosive challenge and brushing simulation, than in group A. There was an increase in mean microhardness in group B which was not significant. Conclusions With the addition of 5% TiO2 to Cention N, there was a significant reduction in surface roughness. The surface microhardness of Cention N containing 5% TiO2 increased non-significantly compared to the control group.

Physical-Chemical and Microhardness Properties of Model Dental Composites Containing 1,2-Bismethacrylate-3-eugenyl Propane Monomer

A new eugenyl dimethacrylated monomer (symbolled BisMEP) has recently been synthesized. It showed promising viscosity and polymerizability as resin for dental composite. As a new monomer, BisMEP must be assessed further; thus, various physical, chemical, and mechanical properties have to be investigated. In this work, the aim was to investigate the potential use of BisMEP in place of the BisGMA matrix of resin-based composites (RBCs), totally or partially. Therefore, a list of model composites (CEa0, CEa25, CEa50, and CEa100) were prepared, which made up of 66 wt% synthesized silica fillers and 34 wt% organic matrices (BisGMA and TEGDMA; 1:1 wt/wt), while the novel BisMEP monomer has replaced the BisGMA content as 0.0, 25, 50, and 100 wt%, respectively. The RBCs were analyzed for their degree of conversion (DC)-based depth of cure at 1 and 2 mm thickness (DC1 and DC2), Vickers hardness (HV), water uptake (WSP), and water solubility (WSL) properties. Data were statistically analyzed using IBM SPSS v21, and the significance level was taken as p < 0.05. The results revealed no significant differences (p > 0.05) in the DC at 1 and 2 mm depth for the same composite. No significant differences in the DC between CEa0, CEa25, and CEa50; however, the difference becomes substantial (p < 0.05) with CEa100, suggesting possible incorporation of BisMEP at low dosage. Furthermore, DC1 for CEa0-CEa50 and DC2 for CEa0-CEa25 were found to be above the proposed minimum limit DC of 55%. Statistical analysis of the HV data showed no significant difference between CEa0, CEa25, and CEa50, while the difference became statistically significant after totally replacing BisGMA with BisMEP (CEa100). Notably, no significant differences in the WSP of various composites were detected. Likewise, WSL tests revealed no significant differences between such composites. These results suggest the possible usage of BisMEP in a mixture with BisGMA with no significant adverse effect on the DC, HV, WSP, and degradation (WSL).

Effect of Different Mouthwashes on the Surface Microhardness and Color Stability of Dental Nanohybrid Resin Composite

BACKGROUND

Surface microhardness and color stability of dental restorative material should be sustained throughout its functional lifetime to maintain the esthetic quality of the restoration. However, the frequent application of mouthwash may affect their surface microhardness and color stability. The aim of this study was to evaluate the effects of different types of mouthwashes with different contents on surface microhardness and color stability of dental nanohybrid resin-based composite.

METHODS

Disc specimens of nanohybrid resin composite (Luna Nano-Hybrid Composite) were prepared according to manufacturing instructions; specimens were incubated for 24 h in three types of mouthwash (Chlorohexidine, Listerine Green Tea, and Colgate Optic White Whitening Mouthwash). Artificial saliva was used as a control group. Surface microhardness was evaluated using Vickers microhardness device. Color stability after and before immersion in the different mouthwashes was evaluated using extra-oral spectrophotometer; the values of color change (ΔE₀₀) were subsequently calculated. Data were analyzed using one-way ANOVA and post hoc test (p ≤ 0.05).

RESULTS

There was no significant difference between microhardness of resin composite immersed in artificial saliva, CHX, and Green Tea mouthwashes (78.5, 78.4, and 73.5, respectively) (p ≥ 0.1), while the bleaching mouthwash led to the lowest microhardness of resin composite, with significant difference compared to the three previous immersion media (p = 0.002). Moreover, there were significant differences in the color changes (ΔE₀₀) of resin composite exposed to the various immersion media (p = 0.0001).

CONCLUSIONS

The bleaching mouthwash led to a significant reduction in nanohybrid resin composite's microhardness compared to the chlorohexidine and Green Tea containing mouthwashes. The resin composite's color change was accepted in bleaching mouthwash but unaccepted in chlorohexidine and Green Tea containing mouthwashes.

The Effect of Different Light-curing Units and Tip Distances on the Polymerization Efficiency of Bulk-fill Materials

PROBLEM STATEMENT

In an average class II posterior preparation, the curing light tip is placed at a distance from the restoration surface that far exceeds the 1-mm manufacturer's recommendation. This distance can have potentially detrimental effects on the curing efficiency of the light-curing unit as well as the properties of the resin-based composite restoration, especially at the bottom of the cavity preparation.

PURPOSE

The purpose of this study was to evaluate the effects of various types of light-curing units (LCUs) and the different curing distances on the degree of conversion (DC) and the surface hardness of bulk-fill composite materials.

METHODS AND MATERIALS

A total of 390 specimens of three resin-based composites (RBCs) were fabricated. Two bulk-fill RBCs, including Filtek Bulk Fill Posterior (3M ESPE GmbH, Seefeld, Germany) and Tetric N-Ceram Bulk Fill (Ivoclar Vivadent AG, Schaan, Liechtenstein), as well as a Filtek Z350 XT nano-filled composite (3M ESPE GmbH, Seefeld, Germany), were utilized. In this study, the Vickers microhardness number (VMN) and the DC were evaluated at 2 and 4 mm thicknesses. Polymerization for 20 seconds was performed using two high-power light-curing units, namely the polywave Bluephase G2 light-emitting diode (LED) LCU (Ivoclar Vivadent AG, Schaan, Liechtenstein) and the monowave Elipar Deep Cure S LED LCU (3M Oral Care, St Paul, MN, USA) at 0, 2, and 4 mm distance between the curing tip and the RBC surface. The results were analyzed using the two-way analysis of variance method. Scheffe's post-hoc multiple comparison tests were used to determine significant differences between the materials, the LCU, and the tip distances.

RESULTS

The highest DC (70.17) was shown by Filtek Bulk Fill Posterior at a distance of 0 mm, whereas the lowest DC (45.99) was measured for the conventional Filtek Z350 XT at a 4 mm distance. Moreover, higher VMNs were shown by Filtek Bulk Fill and Filtek Z350 composites at 0 mm distance than by the Tetric N-Ceram Bulk Fill composite material when cured with a Bluephase G2 LCU. For all materials, a significant decrease in the DC and mean VMN values was observed at a 4 mm distance in comparison with 0 and 2 mm distances.

CONCLUSIONS

The DC and VMN values among the studied bulk fill materials were more significantly affected by the material composition and curing protocols. The increased distance from the light tip has a detrimental effect on the mechanical properties of composite resin materials. Significant differences were observed in the curing efficiency of the two LCUs investigated.

The Effect of Different Light Curing units and Tip Distances on Translucency Parameters of Bulk Fill Materials

Objectives

To evaluate the effect of light curing unit (LCU) types and distance from light curing unit tip on the translucency parameters (TP) of bulk fill composite materials.

Materials and Methods

Two bulk-fill resin composites and one nanohybrid composite were used in this study. The specimens were divided into groups based on the type of curing unit used, and further subdivided based on the distance of the curing source to the surface of the resin composite. Translucency was evaluated at 4 mm thickness (for the bulk-fill) and 2 mm thickness (for nanohybrid) after curing using two different light curing units at zero, 2 mm, and 4 mm distance. The results were analyzed using two-way ANOVA at the significance level of a p-value of < 0.05.

Results

Among all the tested materials, Filtek Bulk Fill Posterior RBC showed the highest TP at 0 mm distance when cured with Blue phase G2 LED LCU and it was the least affected by the differences in distances. However, Filtek Z350 nanohybrid composite had no significant differences between the three distances when cured with Blue phase G2 LCU.

Conclusion

Translucency values among the studied bulk-fill materials are affected by material composition, curing units and the distance of the tip of the light source to the restoration surface.

Effect of Surface Polishing on Nano-Hardness and Elastic Modulus of Different Resin Composites after Immersion in Alcoholic Medium

There has been a great tendency toward using resin composite in dentistry and exploring nano-hardness, elastic modulus, and effect of polishing on its mechanical properties after its artificial ageing. This study aimed to evaluate the effect of surface polishing of four different resin composites on their nano-hardness and elastic modulus. This effect was tested right after light curing of composite resin and after its artificial ageing (immersion in alcoholic medium). Nanoindentation test preparations, surface roughness, surface hardness, and scanning electron microscope were conducted across the four different resin composites: Clearfil AP-X (APX), Estelite Sigma Quick (ESQ), Beautifil II (BE2), and FiltekTM Supreme Ultra Universal restorative (FSU). We found that difference in fillers load and particle size are amongst the factors influencing hardness and modulus of elasticity. The APX is the highest in term of hardness due to fillers load and size while the ESQ is the lowest because all fillers in nano size and distributed homogenously. The significance of surface polishing of the studied resin composite restorations was highlighted. Future research may focus on exploring survival rate of polished and non-polished composite surfaces with emphasis on measuring degree of conversion and impacts of polished and non-polished surfaces on the individuals’ oral health quality of life.

Characterisation of the Filler Fraction in CAD/CAM Resin-Based Composites

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material's mechanical and optical properties.

Influence of radiant exposure values from two third generation LED curing units on polymerization profile and microhardness of orthodontic composite under ceramic and metallic brackets

INTRODUCTION

Third generation of LED light curing units might be used in short exposure periods for orthodontic brackets bonding.

OBJECTIVE

This study evaluated the effect of the different radiant exposure (RE) values: Manufacturers' instructions (MI), ½ MI, 1/4 MI and Turbo mode. Two third-generation LED curing units were used: VALO® and Bluephase 20i® . The degree of conversion (DC) and Vickers hardness (VHN) of an orthodontic composite (OC) (Transbond XT) under metallic (MB) or ceramic brackets (CB) were measured.

METHODS

OC was applied to the bracket base, which was then placed over an attenuated total reflectance (ATR) table coupled to an infrared light spectroscope, or to a glass surface for the VHN analysis. The specimens were light-cured and DC values were calculated. The VHN was obtained in a microhardness tester. The data were analyzed with 2-way ANOVA followed by Tukey's post-hoc test (pre-set α=0.05). Linear regression analysis evaluated the relationship between RE values and dependent variables.

RESULTS

CB allowed higher DC and VHN values than MB (p< 0.001). No significant difference was noted among groups when CB were used. For MB, MI groups showed the highest DC and VHN values. A significant, but weak relationship was found between delivered RE values and dependent variables.

CONCLUSIONS

The decrease in RE values from third generation LED CU did not jeopardize the DC values when CB were used, but can compromise DC and VHN values when MB are used.

Synthesis of an anti-cariogenic experimental dental composite containing novel drug-decorated copper particles

Secondary caries is one of the most major cause for re-placement of dental composite restorations. Targeting the survival of cariogenic bacteria residing on the restoration surface may reduce this problem. The present study aims to evaluate the antibacterial potential as well as assess the physical and chemical properties of experimental dental composites containing novel drug-decorated copper particles (DDCP) as adjunct antibacterial filler particles. These were incorporated at concentrations of 0%, 0.5%, 0.10%, 0.20%, and 0.25% (w/w) into experimental composite consisting of methacrylate monomers and silanized silica fillers. RESULTS: Direct contact test revealed that the anti-cariogenic potential of experimental composites was more than the control groups. The cell viability assay showed no toxic effect on MC3T3-E1 cell lines in the MTT assay. The microhardness of experimental composites increased as the percentage of DDCP increased, however, the degree of cure was increased only up till the concentration of 0.20%. The release kinetics of the composites reveals that even after 28 days there was a steady and slow release of copper particles signifying the sustained anti-cariogenic effect. CONCLUSION: The experimental composites have good anti-cariogenic potential, which was sustained for one month without any deleterious effect on the physical and chemical properties of resin dental composites.