Viscoelastic Properties of Contemporary Bulk-fill Restoratives: A Dynamic-mechanical Analysis

Are S-PRG composites able to resist against erosive and abrasive challenges and protect surrounding enamel in situ?

OBJECTIVES

This study evaluated the resistance of S-PRG (Surface Pre-Reacted Glass-ionomer) composites and other restorative materials against erosive and abrasive challenges and their protective effect on enamel adjacent to the restorations.

MATERIALS AND METHODS

Bovine enamel blocks were prepared and randomized into 12 groups, including 6 types of material, each of them subjected to erosion_e or erosion+abrasion_ea: Beautifil II (S-PRG); Beautifil Bulk Restorative (S-PRG); Filtek Z250 XT; Filtek Bulk Fill; EQUIA Forte; Riva Light Cure. Cavities were prepared in the middle of enamel blocks and restored with the materials. Initial profiling measurement was performed on the material and on adjacent enamel (100, 200, 300, 600 and 700 μm from the restoration margin). Palatal intraoral appliances with the restored enamel blocks were used by the volunteers (n = 10). During 5 days appliances were immersed in 2.5 % citric acid for 2 min; 6 × /day (erosion_e). For ea condition, blocks were brushed for 1 min after each acid immersion. Final profile assessment was performed. Data were analysed by two and three way ANOVA followed by Tukey's test (p < 0.05).

RESULTS

Material wear: Riva Light Cure showed the highest wear followed by EQUIA Forte and then all resin composites, including the ones with S-PRG (p = 0.000). Enamel wear: there was significant interaction among type of restorative material, wear condition and distance (p = 0.014), enamel around materials showed similar wear (p = 0.983) and the enamel subjected to ea exhibited highest wear (p = 0.000).

CONCLUSION

SPRG based composites showed resistance against erosive and abrasive challenges but were not able to protect enamel adjacent to the restorations.

CLINICAL SIGNIFICANCE

S-PRG composites exhibit resistance to material wear comparable to resin composites. However, they have shown an inability to effectively protect the adjacent enamel under in situ erosive-abrasive conditions, despite the presence of mineral-loss-preventing ions surrounding materials.

Evaluation and Comparison of Physical Properties of Cention N with Other Restorative Materials in Artificial Saliva: An In Vitro Study

Objective

The objective of the study was to determine and compare flexural strength and microhardness of Cention N with Glass ionomer cement (GIC) (GC Gold Label Type IX Extra) and Zirconomer improved at a distinctive time period in artificial saliva.

Materials and methods

Cention N, GC Gold Label Type IX Extra, Zirconomer improved for the fabrication of samples. To determine the physical properties such as flexural strength and microhardness, test samples (n-30) of dimensions 12 mm (length)*4 mm (breadth)*2 mm (thickness) were made and divided into three groups. Every sample was dipped for 28 days in a plastic tube containing 5 mL of artificial saliva. Statistical analysis was done using one-way ANOVA with a post hoc test, intergroup and intragroup analyses were carried out.

Results

In an intergroup analysis, flexural strength and microhardness of Cention N were substantially higher than Zirconomer improved and GIC (GC Gold Label Type IX Extra), respectively. In intragroup analysis found that there was a significant decrease (p < 0.001) in the level of flexural strength as well as microhardness after samples were immersed in artificial saliva of group A (Cention N), group B (GC Gold Label Type IX Extra), and group C (Zirconomer improved) from 1st day to 28th day in artificial saliva.

Conclusion

It can be concluded that Cention N had the highest flexural strength and microhardness of the three materials tested. Zirconomer improved can be used as a basic filling material in various restorative procedures due to good comparable mechanical properties and is economical for patients.

How to cite this article

Adsul PS, Dhawan P, Tuli A, et al. Evaluation and Comparison of Physical Properties of Cention N with Other Restorative Materials in Artificial Saliva: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(3):350-355.

S-PRG-based composites erosive wear resistance and the effect on surrounding enamel

This study evaluated Surface Pre-Reacted Glass-ionomer (S-PRG)-based-composites' surface resistance against erosive wear and their protective effect on surrounding enamel. Bovine enamel was randomized into 12 groups (n = 10/group) [erosion (e) or erosion + abrasion (a)]: nanohybrid-S-PRG-based composite (SPRGe/SPRGa), nanohybrid-S-PRG-based bulk-fill (SPRGBFe/SPRGBFa), nanoparticle-composite (RCe/RCa), nanohybrid-bulk-fill (BFe/BFa), Glass Hybrid Restorative System (GHRSe/GHRSa), and resin-modified glass-ionomer-cement (RMGICe/RMGICa). Cavities were prepared and restored. Initial profile assessment was performed on material and on adjacent enamel at distances of 100, 200, 300, 600, and 700 μm from margin. Specimens were immersed in citric acid (2 min; 6×/day for 5 days) for erosion. Erosion + abrasion groups were brushed for 1 min after erosion. Final profile assessment was performed. Two-way ANOVA and Tukey-test showed: for erosion, the GHRSe and RMGICe presented greater material wear compared to the other groups (p = 0.001); up to 300 μm away from restoration, GHRSe and SPRGBFe were able to prevent enamel loss compared to RMGICe and other composite groups (p = 0.001). For erosion + abrasion, none of the materials exhibited a significant protective effect and S-PRG-based groups showed lower wear than RMGICa and GHRSa, and higher wear than composites (p = 0.001). S-PRG-based-composites can diminish surrounding enamel loss only against erosion alone, similarly to GIC, with advantage of being a more resistant material.

Changes in color and contrast ratio of resin composites after curing and storage in water

Purpose

To verify the color change and contrast ratio of resin composites after curing and after 30 days of storage in water.

Methods

Dentin A2 shades of different light-cured dental resin composites (Vittra APS, FGM, Brazil; Z350 XT, 3M ESPE, EUA; Tetric N-Ceram, Ivoclar Vivadent, Liechtenstein, and Charisma Diamond, Heraeus Kulzer, Germany) were tested. Ten rounded specimens (8 mm × 2 mm) were prepared for each material. Reflectance for all samples was obtained using a spectrophotometer (Minolta CM 3700d, Konica Minolta, Japan) before curing, immediately after curing, and after 30 days of storage in water. The color change (ΔE*lab) and contrast ratio (CR) data were analyzed using a one-way analysis of variance with Tukey's and paired t-tests (α = 1%).

Results

For all materials tested, significant color changes were noticeable after curing and after 30 days in water (p < 0.01). Significant changes in the CR values before curing, after curing, and 30 days of storage in water were observed in the resin composites investigated (p < 0.01) except for Z350 (p > 0.01).

Conclusion

The CR values and color changes after curing and 30 days of storage in water varied depending on the material tested. This study corroborates the clinical practice of curing a small amount of unpolymerized resin composite on the tooth surface to select the desired shade before undertaking esthetic restorative procedures.

Structural, Physical, and Mechanical Analysis of ZnO and TiO2 Nanoparticle-Reinforced Self-Adhesive Coating Restorative Material

This study aimed to modify an EQUIA coat (EC; GC, Japan) by incorporating 1 and 2 wt.% of zinc oxide (ZnO; EC-Z1 and EC-Z2) and titanium dioxide (TiO₂; EC-T1 and EC-T2) nanoparticles, whereby structural and phase analyses were assessed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Thermogravimetric analysis/differential scanning calorimetry, micro-hardness, and water absorption analyses were conducted, and the microstructure was studied by scanning electron microscopy/energy-dispersive spectroscopy. FTIR spectra showed a reduction in peak heights of amide (1521 cm^-1) and carbonyl (1716 cm^-1) groups. XRD showed peaks of ZnO (2θ ~ 31.3°, 34.0°, 35.8°, 47.1°, 56.2°, 62.5°, 67.6°, and 68.7°) and TiO₂ (2θ ~ 25.3°, 37.8°, 47.9, 54.5°, 62.8°, 69.5°, and 75.1°) corresponding to a hexagonal phase with a wurtzite structure and an anatase phase, respectively. Thermal stability was improved in newly modified materials in comparison to the control group. The sequence of obtained glass transitions was EC-T2 (111 °C), EC-T1 (102 °C), EC-Z2 (98 °C), EC-Z1 (92 °C), and EC-C (90 °C). EC-T2 and EC-T1 showed the highest (43.76 ± 2.78) and lowest (29.58 ± 3.2) micro-hardness values. EC showed the maximum water absorption (1.6%) at day 7 followed by EC-T1 (0.82%) and EC-Z1 (0.61%). These results suggest that EC with ZnO and TiO₂ nanoparticles has the potential to be used clinically as a coating material.

Evaluation of the bond strengths of restorative materials to primary tooth dentin treated with different pulpotomy techniques

The aim of this study was to investigate the changes of different pulpotomy techniques on the primary tooth dentin and to evaluate the effects of these pulpotomy methods on the shear bond strength of restorative materials to primary tooth dentin. Two hundred and forty dentin specimens were distributed randomly to the study groups as; control, ferric sulphate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma (APCP). After the application of pulpotomy methods, samples were again randomly divided to two restorative materials (glass hybrid and composite resin) (n = 20) and shear bond strength (SBS) test was performed. Then, 12 new dentin specimens were prepared for all groups for surface analysis. Surface examination (n = 12) and fracture analyses (n = 240) were carried out with scanning electron microscope (SEM). Statistical significance range was accepted as α <.05 for all data. A statistically significant difference was obtained among all study groups for glass hybrid material as well as composite material (p <.05). While the highest mean SBS value was obtained with Nd:YAG laser (7.58 ± 0.60 MPa), the lowest value was observed with Biodentine® (6.70 ± 0.91 MPa; p = .001) for glass hybrid material. For composite material, the highest mean SBS value was calculated for Nd:YAG laser (13.79 ± 1.24 MPa), while the lowest value was obtained with ferric sulphate (10.17 ± 1.45 MPa; p = .001). Fracture modes were mainly adhesive and mixed type according to SEM analysis. Moreover, morphological changes were observed with SEM on the dentin surfaces of ferric sulphate, Biodentine® and Nd:YAG laser. Within the limitations of this study, Nd:YAG laser increased the shear bond strength values in groups of composite resin. RESEARCH HIGHLIGHTS: In this article, we report the results of the shear bonding strength test of two restorative materials (glass-hybrid vs. composite resin) to primary tooth dentin following the application of five different pulpotomy techniques (ferric sulfate, Biodentine® , Nd:YAG laser, photobiomodulation, and atmospheric pressure cold plasma) were reported. This article will contribute to the literature that there are considerably limited researches concerning the bond strength of glass hybrid to primary dentin and also atmospheric pressure cold plasma in pulpotomies. The SEM examination was performed in two stages in this study; the morphological changes in both treated dentin surfaces and the surfaces of the samples subjected to the shear bond strength test.

Influence of polymerization pressure and post-cure treatment on conversion degree and viscoelastic properties of polymer infiltrated ceramic network

This study aimed at determining an optimum polymerization pressure for Polymer Infiltrated Ceramic Network (PICN) blocks by characterizing the conversion degree (DC) and the viscoelastic properties of experimental PICN blocks polymerized at 90 °C under various high pressures followed or not by post-cure treatment (PC). Near infrared analysis and dynamic mechanical analysis were used to characterize DC and viscoelastic properties of sixteen PICN: one control (thermo-cured) and fifteen experimental groups (one thermo-cured followed by PC and fourteen high pressure polymerized PICN, in the range of 50-350 MPa without and with PC). Conversion degree of high pressure polymerized PICN blocks without post curing displays an optimum between 100 and 150 MPa resulting in an improved E' and T_g. Post curing induces a higher DC with a controversial effect on thermomechanical properties. The results suggested that 100-150 MPa without PC is an optimum polymerization parameter, resulting in PICN blocks with significantly better DC, T_g, E'.

In vitro wear of (resin-coated) high-viscosity glass ionomer cements and glass hybrid restorative systems

OBJECTIVES

The aim of the present study was to investigate the volumetric abrasive wear of a high-viscosity glass ionomer cement (hvGIC; Equia Fil) and a glass hybrid restorative system (ghRS; Equia Forte), each being recommended as amalgam alternatives. Both materials were applied with or without their respective resinous coating, and were compared with a conventional GIC (Ketac Fil) and a hybrid composite resin (CR; G-ænial Posterior).

METHODS

78 standardized occlusal Class I cavities were restored with the various materials (n = 13 per group). Before and after chewing simulation (30,000 cycles at 40 N), each sample underwent optical scanning procedures (Omnicam). A comparison of the total wear using a fluorescence-aided identification technique (OraCheck) followed, and differences (α = 5%) between groups were compared by means of MANOVA.

RESULTS

Regarding the wear rates of hvGIC and ghRS, no differences could be observed (p > .050), and this was not affected by the resinous coating. All hvGIC and ghRS restorations showed significantly higher abrasive wear than CR (p < .001), while the conventional GIC displayed a significant underperformance compared with any other material (p < .001).

CONCLUSIONS

Resinous coating of hvGIC or ghRS does not appear to exert an effective long-term protection against advanced abrasive wear. Compared to the conventional GIC showing a considerable substance loss, both hvGIC and ghRS materials revealed an improved abrasion resistance, but clearly failed to meet the excellent values of the CR.

CLINICAL SIGNIFICANCE

Occlusal loading should be carefully considered when using hvGIC or ghRS as amalgam (or composite resin) alternatives for the restoration of posterior teeth.

Effect of Saliva Contamination on Microleakage of Open Sandwich Restorations

Objectives

The purpose of the present study was to evaluate the microleakage of conventional glass-ionomer, resin modified glass-ionomer and glass hybrid ionomer Class II open sandwich restorations with or without saliva contamination.

Materials and methods

Sixty extracted sound human molar teeth were used and 120 class II slot cavities were prepared in mesial and distal surfaces. The gingival margins were located 1 mm below the cementoenamel junction. All specimens were randomly divided in 4 groups (n=15): Group I: High-Viscous Glass Ionomer (Fuji IX GP) Group II: Resin Modified Glass Ionomer (Fuji II LC) Group III: Glass Hybrid Ionomer (Equia-fil Forte), Group IV: Composite Resin (G'aenial Posterior). In open sandwich restoration groups, glass ionomer materials were placed to gingival floor in 1 mm thickness and rest of the cavity was filled with resin composite. After the restorations in mesial surfaces had been performed, distal cavities were restored with the same protocol after saliva contamination. The specimens were thermo-cycled for 10000 cycles at 5⁰C to 55⁰C and immersed in methylene blue dye solution (% 0,5) for 24 hours. Then, they were sectioned vertically through the center of the restorations from mesial to distal surface with a water-cooled diamond saw with 1mm thickness. Subsequently, the dye penetration was evaluated with image analysis software. Data were statistically analyzed (p<0.05).

Results

There was a statistically significant difference between gingival microleakage scores in no contamination groups, between high-viscous glass ionomer, Fuji IX GP and other materials tested (p<0.05). In saliva contaminated groups, there was no statistically significant difference between gingival microleakage scores (p>0.05). Additionally, there was not a statistically significant difference between the no contamination and saliva contaminated groups regardless of dental materials tested (p>0.05).

Conclusion

Within the limitations of this study, in open sandwich restorations, saliva contamination did not show an adverse effect on microleakage irrespective of dental materials tested. Glass hybrid ionomers and resin modified glass ionomers showed lower microleakage scores in gingival margins compared to high-viscous glass ionomer material in no contamination groups.

Effect of resin coating on highly viscous glass ionomer cements: A dynamic analysis

OBJECTIVES

This study determined the effects of self-adhesive resin coatings on viscoelastic properties of highly viscous glass ionomer cements (HVGICs) using dynamic mechanical analysis.

MATERIALS AND METHODS

The HVGICs evaluated were Zirconomer [ZR] (Shofu), Equia Forte [EQ] (GC) and Riva [RV] (SDI). Sixty specimens (12mm x 2mm x 2mm) of each material were fabricated using customized Teflon molds. After initial set, the specimens were removed from their molds, finished, measured and randomly divided into 3 groups of 20. Half the specimens in each group were left uncoated while the remaining half was covered with the respective manufacturers' resin coating. The specimens were subsequently conditioned in distilled water, artificial saliva or citric acid at 37°C for 7 days. The uncoated and coated specimens (n=10) were then subjected to dynamic mechanical testing in flexure mode at 37°C with a frequency of 0.1 to 10Hz. Storage modulus, loss modulus and loss tangent data were subjected to normality testing and statistical analysis using one-way ANOVA/Scheffe's post-hoc test and Ttest at significance level p<0.05.

RESULTS

Mean storage modulus ranged from 1.39 ± 0.36 to 10.80 ± 0.86 GPa while mean loss modulus varied from 0.13 ± 0.03 to 0.70 ± 0.14 GPa after conditioning in the different mediums. Values for loss tangent ranged from 39.4 ± 7.75 to 213.2 ± 20.11 (x10 -3 ). Significant differences in visco-elastic properties were observed between mediums and materials. When conditioned in distilled water and artificial saliva,storage modulus was significantly improved when ZR, EQ and RV were uncoated. Significantly higher values were, however, observed with resin coating when the materials were exposed to citric acid.

CONCLUSION

The visco-elastic properties of HVGICs were influenced by both resin coating and chemical environment.

Clinical Performance of a Glass Hybrid Restorative in Extended Size Class II Cavities

Objective:

To evaluate the clinical performance of a glass hybrid restorative compared with a resin composite in the restoration of large and deep Class II cavities after 24 months.

Methods and Materials:

A total of 108 extended size, with the width of the proximal box not interfering with the peak of the cusps and the proximal box in occlusion, Class II lesions in 37 patients were either restored with a glass hybrid restorative or with a micro-hybrid composite resin in combination with selective etching by two experienced operators according to the manufacturer's instructions. Two independent examiners evaluated the restorations at baseline and at the six-, 12-, 18-, and 24-month recalls according to the modified US Public Health Service criteria. Negative replicas at each recall were observed under scanning electron microscopy (SEM) to examine surface characteristics. Data were analyzed statistically.

Results:

After 24 months, 90 restorations were evaluated in 32 patients (recall rate: 86.5%). Four glass hybrid restorations were missing; three were due to bulk and one was due to proximal fracture at 12 months. Only six restorations were scored as bravo at baseline and at the six-, 12-, 18-, and 24-month recalls for color (p&lt;0.05). No significant differences were observed between the two restorative materials for the other criteria evaluated (p&gt;0.05). SEM observations exhibited acceptable surface and marginal adaptation characteristics for both restorative materials at 24 months.

Conclusions:

Although glass hybrid restorations showed significant mismatch in color, both restorative materials exhibited successful performance for the restoration of large Class II cavities after 24 months.

Dynamic Viscoelastic Characterization of Bulk-fill Resin-based Composites and Their Conventional Counterparts

This study compared the viscoelastic properties of restorative and flowable bulk-fill resin-based composites (RBCs) with their conventional counterparts and evaluated the impact of aqueous solutions on viscoelastic properties. The materials examined included three conventional RBCs (Filtek Z350, Tetric N Ceram, and Beautifil II), three restorative bulk-fill RBCs (Filtek Bulk-Fill Restorative, Tetric N Ceram Bulk-Fill, and Beautifil Bulk-Fill Restorative) in addition to three flowable bulk-fill RBCs (Filtek Bulk-Fill Flowable, Tetric N Flow Bulk-Fill, and Beautifil Bulk-Fill Flowable). Beam-shaped specimens (12×2×2 mm) were fabricated using customized stainless-steel molds, finished, and measured. The specimens were randomly divided into four groups and conditioned in air (control), artificial saliva, 0.02 N citric acid, and 50% ethanol-water solution for seven days at 37°C. They were then subjected to dynamic mechanical analysis (n = 10) in flexure mode at 37°C with a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to statistical analysis using one-way analysis of variance/Tukey post hoc test at a significance level of α = 0.05. Viscoelastic properties of the RBCs were found to be product and conditioning medium dependent. For most RBCs, exposure to aqueous solutions, particularly an ethanol-water solution, degraded viscoelastic properties. With the exception of Filtek Bulk-Fill Restorative, bulk-fill restorative and flowable RBCs generally had significantly lower storage and loss modulus than their conventional counterparts regardless of conditioning medium. Conventional RBCs are thus favored over their bulk-fill counterparts, particularly for high-stress-bearing areas.

Comparative evaluation of compressive strength and surface microhardness of EQUIA Forte, resin-modified glass-ionomer cement with conventional glass-ionomer cement

PURPOSE

The study aimed to evaluate and compare the compressive strength and surface microhardness of EQUIA Forte, light cure, and conventional glass-ionomer cement (GIC).

METHODOLOGY

Fifty-four pellets of G-Coat (GC) Gold Label 2, GC Gold Label light-cured universal restorative material, and EQUIA Forte GIC were prepared of dimensions (6 × 4) mm and were divided into three groups (18) each and were stored at 37°C for 1 h and then immersed in 20 ml of deionized water, artificial saliva, and lactic acid six each, respectively, over 30 days. Samples were subjected to surface microhardness and compressive strength test on the 1^st day, 7^th day, and 30^th day. Results were subjected to ANOVA and Bonferroni post hoc test.

RESULTS

Comparing the compressive strength of EQUIA Forte from day 1 to 30 when placed in artificial saliva, there was a significant increase on day 30 (P = 0.007); compared to other groups. The surface microhardness of EQUIA Forte from day 1 to 30 when placed in artificial saliva nonsignificantly decreased comparing to other groups.

CONCLUSION

Surface microhardness and compressive strength of EQUIA Forte were significantly high in comparison to the other groups.