Effect of surface treatments on the mechanical properties and antimicrobial activity of desiccated glass ionomers

Effect of aging on mechanical and antibacterial properties of fluorinated graphene reinforced glass ionomer: In vitro study

OBJECTIVES

This study: 1) aims to test the mechanical and antibacterial properties of fluorinated graphene strengthened glass ionomer materials (FG/GICs); 2) aims to investigate the effects of thermo-cycling on (FG/GICs).

MATERIALS AND METHODS

Fluorinated graphene (FG) with bright white color was prepared from fluorinated graphite (SIGMA Aldrich), using modified Hummer's method, to be added to conventional glass ionomer cements (GICs). In addition to a control group (group 1), experimentally modified GICs were prepared by adding FG to the conventional glass ionomer powder with three different weight ratios; (group 2, 1 wt %; group 3, 2.5 wt %; and group 4, 5 wt %) using mechanical blending method. Experimental groups of the specimens (n = 240) were divided, for each concentration (n = 120) half of the specimens were subjected to thermo-cycling. Hardness, compressive strength, and antibacterial activity of (FG/GICs) were measured with and without thermo-cycling. Compressive strength was measured by a universal testing machine, hardness was measured using a Vickers micro-hardness tester, and antibacterial effects against staphylococcus aureus and streptococcus mutans were tested by the pellicle sticking method. For statistical analysis, numerical data were explored for normality and variance homogeneity using Shapiro-Wilk and Leven's tests respectively.

RESULTS

The prepared (FG/GICs) showed an increase in hardness in group 4 (p < 0.001). Groups 3 and 4 gave the highest compressive strength values with no significant difference between them (p < 0.001). Groups 2, 3, and 4 showed improved antibacterial activity with no statistical difference between them (p > 0.001). Results after thermo-cycling showed significantly decreased hardness, and compressive strength values (p < 0.001), however, the results of antibacterial activity against streptococcus mutans showed no statistical difference after thermo-cycling (group 2, p = 0.05; group 3, p = 0.18; group 4, p = 0.26). The same results were observed for antibacterial activity against staphylococcus aureus (p = 0.92, p = 0.14, and p = 0.48 respectively).

CONCLUSION

FG can be considered a promising additive to GICs to promote its anti-cariogenic effects, however, these antibacterial effects are only useful in the short term, as aging adversely affected their mechanical properties. The 2.5 wt % FG/GICs is suggested to be the most encouraging, as after aging, it represented the highest compressive strength among all groups, while its hardness values were at least comparable to that of conventional glass ionomer.

CLINICAL SIGNIFICANCE

FG/GICs can be considered an anti-cariogenic restoration in temporary restorative interventions, as in certain cases in deciduous teeth where considerable esthetics may be required, especially those with difficult moisture control, where neither resin composite restorations nor amalgam restorations will be indicated. It can also be used for patients with high caries index or in atraumatic restorative treatment (ART) in low-income countries.

Effect of bacterial resistant zwitterionic derivative incorporation on the physical properties of resin-modified glass ionomer luting cement

Biofilms induce microbial-mediated surface roughening and deterioration of cement. In this study, zwitterionic derivatives (ZD) of sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine, were added in concentrations of 0, 1, and 3% to three different types of commercially available resin-modified glass ionomer cement (RMGIC) (RMC-I: RelyX Luting 2, RMC-II: Nexus RMGI, and RMC-III: GC FujiCEM 2). The unmodified RMGICs served as the control group for comparison. The resistance of Streptococcus mutans to ZD-modified RMGIC was evaluated with a monoculture biofilm assay. The following physical properties of the ZD-modified RMGIC were assessed: wettability, film thickness, flexural strength, elastic modulus, shear bond strength, and failure mode. The ZD-modified RMGIC significantly inhibited biofilm formation, with at least a 30% reduction compared to the control group. The addition of ZD improved the wettability of RMGIC; however, only 3% of the SBMA group was statistically different (P < 0.05). The film thickness increased in proportion to the increasing ZD concentrations; there was no statistical difference within the RMC-I (P > 0.05). The experimental groups' flexural strength, elastic modulus, and shear bond strength showed an insignificant decrease from the control group; there was no statistical difference within the RMC-I (P > 0.05). The mode of failure differed slightly in each group, but all groups showed dominance in the adhesive and mixed failure. Thus, the addition of 1 wt.% ZD in RMGIC favorably enhanced the resistance to Streptococcus mutans without any tangible loss in flexural and shear bond strength.

Effect of Fluoride-based Varnishes with Added Calcium and Phosphate on Microhardness of Esthetic Restorative Materials: An In Vitro Study

Background and objectives

Fluoride varnishes are being used to prevent caries in children. The high concentration of fluoride in varnishes apart from caries prevention may cause changes in surface properties of esthetic restorations. The study aims to evaluate and compare the effect of four commercially available fluoride varnishes with added calcium and phosphate on microhardness of three esthetic materials namely conventional GIC (Fuji II), high viscosity GIC (Fuji IX), and nanocomposite (Filtek Z350).

Materials and methods

A total of 28 pellets were made of each material and stored in distilled water at 37 °C for 48 hours. The microhardness of the pellets was tested which served as a baseline. These were then randomly divided into four subgroups. In one subgroup Profluorid varnish was applied, second subgroup MI varnish was applied, third subgroup Embrace varnish was applied, and in the fourth subgroup Enamel Pro varnish was applied as per protocol. Thereafter, all the pellets were subjected to microhardness testing (load = 100 g for 15 seconds).

Results

The fluoride varnishes increased the microhardness of conventional GIC (Fuji II) whereas in case of high viscosity GIC (Fuji IX) the application of varnishes reduced the microhardness. In case of nanocomposite restorative material (Filtek Z350) only Profluorid varnish increased its microhardness.

Conclusion

Fluoride varnish and calcium-phosphate containing fluoride varnish effect on the microhardness of restorative material is material dependent. So, the choice of fluoride varnish with or without proprietary additives depends on the nature and composition of the restorative material.

How to cite this article

Shetty RS, Bhat SS, HK Sundeep, et al. Effect of Fluoride-based Varnishes with Added Calcium and Phosphate on Microhardness of Esthetic Restorative Materials: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(2):187-193.

Effects of theobromine addition on chemical and mechanical properties of a conventional glass ionomer cement

In vitro effect of 1% theobromine addition on the physical and chemical properties of conventional glass ionomer (GIC) cement was investigated. Conventional GIC (GIC-C) and 1% theobromine added to GIC (GIC-THEO) specimens were compared regarding the microhardness (n = 10), sorption (n = 5), solubility (n = 5), color change (n = 10), fluoride release in saliva (n = 10) and the amount of biofilm deposition (n = 20). Compared against conventional GIC, adding 1% theobromine increased microhardness (p < 0.05), while its sorption, solubility, color and fluoride release to saliva (p > 0.05) remained unchanged. On the other hand, Streptococcus mutans biofilm amount deposited on its surface decreased statistically when theobromine was added to GIC (p < 0.05). Based on the results, it could be concluded that 1% theobromine addition to GIC can be a good strategy as it keeps some of its properties and improves microhardness and biofilm deposits strengthening its role in the preventive approach of dentistry.

In vitro antibacterial activity of self-etch bio-active dental adhesives after artificial aging

Purpose:

The aims to evaluate the antibacterial effect of different bioactive component containing dental adhesives before and after artificial aging.

Materials and methods:

Two bio-active adhesives; Clearfil Protect Bond and FL Bond II, two non-bioactive adhesives, Clearfil SE Bond and Clearfil S3 Bond were used for this study. Antibacterial activities of the fresh and aged samples against Streptococcus mutans were investigated with Direct Contact Test. Data were analyzed with Kruskal Wallis and Mann Whitney U multiple comparison tests.

Results:

For fresh samples FL Bond II and Clearfil Protect Bond exhibit similar antibacterial effect but Clearfil Protect Bond showed significantly higher antibacterial effect after aging the samples (p<0.05).

Conclusion:

The incorporation of bio-active antibacterial components into adhesive systems may be considered as a fundamental component in inhibiting residual Streptococcus mutans when considering the antibacterial effect of fresh samples of bio-active adhesives.

Effect of a hyperbaric environment (diving conditions) on adhesive restorations: an in vitro study

Objectives No recent study has addressed the effect of diving conditions (pressure increase) on adhesive restorations. We evaluated the impact of a simulated hyperbaric environment on microleakage of the dentine-composite resin interface. The ultimate aim was to propose recommendations for restorative dentistry for patients who are divers to limit barodontalgia (dental pain caused by pressure variations of the environment) and may lead to dangerous sequelae.Methods We bonded 20 dentine disks by using an adhesive system (Scothbond Universal) to ten intact composite cylinders and ten composite cylinders with porosity (Ceram X mono). For each group, the samples were divided into two subgroups, one submitted to a simulated hyperbaric environment and the other to an ambient environment. All samples were immersed in a silver nitrate solution to evaluate microleakage at the interface after analysis with a camera.Results Dye percolation for groups in the hyperbaric environment was greater than groups in ambient environment. For each subgroup, dye percolation was greater for samples with than without porosity.Conclusions High percolation percentages demonstrate that our simulated hyperbaric condition led to loss of sealing at the dentine-composite resin interface, especially with porous composites.Clinical significance Respect of the protocol and the quality of condensation for adhesive restorations are important in all clinical situations, especially for patients who are divers. A more interventionist approach must be adopted with these patients.