Comparison between the effect of adding microhydroxyapatite and chitosan on surface roughness and Microhardness of resin modified and conventional glass ionomer cements

Prevention of secondary caries using fluoride-loaded chitosan nanoparticle-modified glass-ionomer cement

OBJECTIVE

To study the effect of incorporating chitosan and fluoride-loaded chitosan nanoparticles into a glass-ionomer cement (GIC) to prevent secondary caries.

MATERIALS AND METHODS

A standard cervical cavity (mesio-distal width 6 mm, cervico-occlusal width 2 mm, and depth 2 mm) was prepared on 30 molars for the following restoration groups: group 1, conventional GIC restoration; group 2, chitosan (10%) modified GIC restoration; group 3, fluoride loaded chitosan nanoparticles (10%) modified GIC restoration. The restored teeth were subjected to 1,500 thermal cycles before undergoing a multi-species cariogenic biofilm challenge. The restored teeth were examined by micro-computed tomography (micro-CT), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). Data were analyzed by the one-way ANOVA, Tukey HDS, Kruskal Wallis, and Dunn's test.

RESULTS

Micro-CT determined outer lesion depths for groups 1-3 were: 614 ± 20 μm, 589 ± 17 μm, and 560 ± 19 μm respectively. Both modifications with chitosan and fluoride-loaded chitosan nanoparticles significantly affected outer lesion depth (p < 0.05). The modification with fluoride-loaded chitosan nanoparticles statistically significantly decreased the outer lesion depth compared to all other groups (p < 0.05). SEM/EDX showed an increase of calcium, phosphorus, and fluoride at the root dentine adjacent to the restoration in groups 2 and 3 (modified GIC). This increase was statistically significantly higher in the group modified with fluorine-loaded nano chitosan particles compared to the other groups (p < 0.05).

CONCLUSION

Incorporation of 10% chitosan and 10% fluoride-loaded chitosan nanoparticles into GIC restorative material can prevent secondary root caries development. 10% fluoride-loaded chitosan nanoparticles were more effective.

CLINICAL SIGNIFICANCE

Glass ionomer cement modified with fluoride-loaded chitosan nanoparticles may be a promising restorative material in pediatric and preventive dentistry due to their controlled release properties.

Effect of Graphene Oxide Nanoparticles Incorporation on the Mechanical Properties of a Resin-Modified Glass Ionomer Cement

The objective of this study was to evaluate the effect of incorporating different concentrations of graphene oxide (GO) nanoparticles on the mechanical properties of a resin-modified glass ionomer cement (RMGIC). A commercial RMGIC (Resiglass R, Biodinâmica) was modified by incorporating 0.1% and 0.5% (by weight) of GO into the powder's material. An unmodified RMGIC was used as a control group. Powder samples were characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Specimens were fabricated and subjected to flexural strength (n = 15), modulus of elasticity (n = 15), Vicker's microhardness (n = 10), and surface roughness tests (n = 10). Data were analyzed using one-way ANOVA and Tukey's post hoc test (α = 5%). Experimental groups' powder demonstrated a homogeneous dispersion of GO. No statistically significant difference was observed in flexural strength (p = 0.067) and modulus of elasticity (p = 0.143) tests. The groups containing 0.1% and 0.5% GO showed significantly higher microhardness and lower surface roughness values (p < 0.001) compared to the control group. The incorporation of GO nanoparticles at concentrations of 0.1% and 0.5% improved the microhardness and surface roughness without negatively affecting the flexural strength and modulus of elasticity of an RMGIC.

Effect of Incorporating Date Seeds Microparticles on Compressive Strength and Microhardness of Conventional Glass Ionomer (an In VitroStudy)

Background

This study aimed to evaluate the effect of incorporating date seeds (DS) microparticles on the compressive strength and microhardness of conventional glass ionomer cement properties following aging in artificial saliva.

Material and Methods

Date seeds powder was prepared and added to the conventional glass ionomer cement at concentrations of 3% and 5% by weight. To prepare the samples, a silicon mold was utilized, with dimensions of 6 mm in height and 4 mm in diameter. These samples were then divided into three main groups: group I; unmodified GICs serving as the control, group II; GICs with a 3% weight of DS, and group III; GICs with a 5% weight of DS. The compressive strength and microhardness of the samples were subsequently measured and compared across the three groups, after being stored in artificial saliva for two different time intervals: one day and 30 days. Fourier transform infrared (FTIR) analysis was conducted to determine the nature of the DS and the GIC-DS composite. At the same time, a scanning electron microscope (SEM) was employed to investigate the surface characteristics of the samples.

Results

The measurement values after 24 hours showed that the DS addition had significantly increased the compressive strength but had no effect on the microhardness. However, after aging there was a significant increase in the microhardness and a significant decrease in the compressive strength of the DS groups compared to the control group.

Conclusions

The addition of date seeds powder showed an enhancing effect on the microhardness over time but adversely affected the compressive strength of the material. Key words:Artificial saliva, natural resources, waste materials, dental restoration, mechanical properties.

Assessing the Impact of Nano-Graphene Oxide Addition on Surface Microhardness and Roughness of Glass Ionomer Cements: A Laboratory Study

Background

Nanomaterials, including nano-graphene oxide (nGO), have emerged as promising modifiers for dental materials. Therefore, this study investigated the effect of incorporating nGO into conventional glass ionomer cement (CGIC) and resin-modified glass ionomer cement (RMGIC) on surface roughness and hardness.

Methods

Sixty disk-shaped specimens (2 × 6 mm) were divided into six groups: CGIC, RMGIC, CGIC with 1 wt.% nGO, CGIC with 2 wt.% nGO, RMGIC with 1 wt.% nGO, and RMGIC with 2 wt.% nGO. Surface roughness (Ra) and Vickers microhardness (VHN) were measured using a surface profilometer and Vickers microhardness tester, respectively. Statistical analysis employed the Kruskal-Wallis and Mann-Whitney tests (p <0.05).

Results

The microhardness of RMGICs significantly increased with 1% and 2% nGO (p=0.017, P=0.001, respectively), while CGICs showed a significant decrease in VHN with nGO incorporation (p=0.001). VHN values of all CGIC groups were significantly higher than those of all RMGIC groups (p=0.001). Mean surface roughness values for all CGICs were significantly higher than those of RMGIC groups (p=0.001). Within the RMGIC groups, mean Ra values of RMGIC + 1 wt.% nGO and RMGIC + 2 wt.% nGO groups decreased significantly compared to the RMGIC control group (p=0.001, p=0.001, respectively). Among CGIC groups, mean Ra values of 1 wt.% and 2 wt.% nGO/CGIC groups were significantly higher than the CGIC control group (p=0.016, p=0.001).

Conclusion

Incorporating nGO into RMGICs increased surface microhardness while reducing surface roughness, offering potential advantages for clinical applications. Conversely, adding nGO to CGICs increased surface roughness and decreased surface hardness. These findings emphasize the potential benefits of utilizing nGO in RMGICs and their implications in clinical practice.

Micro-shear bond strength of a novel resin-modified glass ionomer luting cement (eRMGIC) functionalized with organophosphorus monomer to different dental substrates

Objectives

This study aims to assess and compare the micro-shear bond strength (μSBS) of a novel resin-modified glass-ionomer luting cement functionalized with a methacrylate co-monomer containing a phosphoric acid group, 30 wt% 2-(methacryloxy) ethyl phosphate (2-MEP), with different substrates (dentin, enamel, zirconia, and base metal alloy). This assessment is conducted in comparison with conventional resin-modified glass ionomer cement and self-adhesive resin cement.

Materials and methods

In this in vitro study, ninety-six specimens were prepared and categorized into four groups: enamel (A), dentin (B), zirconia (C), and base metal alloys (D). Enamel (E) and dentin (D) specimens were obtained from 30 human maxillary first premolars extracted during orthodontic treatment. For zirconia and metal alloys, 48 disks were manufactured using IPS e.max ZirCAD through dry milling and Co-Cr powder alloy by selective laser milling. Each group was further subdivided into three subgroups (n = 8) according to the luting cement used: (1) Fuji PLUS resin-modified glass ionomer luting cement (FP) as a control cement, (2) modified control cement (eRMGIC), and (3) RelyX U 200 (RU 200) self-adhesive resin cement. The two-way analysis of variance and Tukey's HSD were used to assess the data obtained from measuring the μSBS of the samples.

Results

The results of this study showed that the mean μSBS values of eRMGIC were statistically higher compared to FP in all tested groups (p < 0.001). The mean μSBS results of eRMGIC were non-significantly different from those recorded by RU 200 for all substrates except for the dentin substrate, where the RU200 cement produced significantly higher strength (p < 0.001). The failure modes were limited to a combination of mixed and adhesive failures without pure cohesive failure.

Significance

The functionalization of FP with an organophosphorus co-monomer (2-MEP) directly affects the adhesion performance of the functionalized cement, which may be utilized to develop a new type of acid-base cement. It exhibited a performance comparable to that of resin-based cement and should serve well under different clinical conditions.

Assessing the Influence of Thermocycling on Compressive Strength, Flexural Strength, and Microhardness in Green-Mediated Nanocomposite-Enhanced Glass Ionomer Cement Compared to Traditional Glass Ionomer Cement

Background and objective Glass ionomer cement (GIC), also known as polyalkenoate cement, has been extensively used in dentistry for both luting and restorative purposes. Despite being the first choice for aesthetic restorations due to their chemical bonding ability to teeth, GICs have faced challenges such as low mechanical properties, abrasion resistance, and sensitivity to moisture, leading to the search for improved materials.  This study aims to assess the effects of thermocycling on the compressive, flexural strength, and microhardness of green-mediated nanocomposite-modified GIC in comparison to traditional GIC. Methodology Green-mediated nanoparticles, consisting of chitosan, titanium, zirconia, and hydroxyapatite (Ch-Ti-Zr-HA), were synthesized using a one-pot synthesis technique to form nanocomposites. These nanocomposites were then incorporated into GIC specimens in varying concentrations (3%, 5%, and 10%), denoted as Group I, Group II, and Group III, respectively. Group IV served as the control, consisting of conventional GIC. To assess the performance of the novel restorative materials over an extended period, compressive strength, flexural strength, and microhardness were measured before and after thermocycling using a universal material testing machine. Furthermore, scanning electron microscopy (SEM) analysis was carried out following the thermocycling process. The collected data were subjected to statistical analysis through one-way analysis of variance (ANOVA) and paired t-tests. Results  The findings demonstrated that, in comparison to the control group, both the mean compressive strength and flexural strength, as well as hardness, were notably higher for the 10% and 5% nanocomposite-modified GIC specimens before and after thermocycling (P < 0.05). Notably, there was no notable difference observed between the 5% and 10% concentrations (P > 0.05). These results suggest that incorporating green-mediated nanocomposites (Ch-Ti-Zr-HA) modified GIC at either 5% or 10% concentration levels leads to improved mechanical properties, indicating their potential as promising alternatives in dental restorative materials. Conclusions Based on our findings, it can be inferred that the 10% and 5% concentrations of green-mediated (Ch-Ti-Zr-HA) modified GIC exhibit superior compressive and flexural strength compared to conventional GIC. Additionally, analysis of the scanning electron microscope (SEM) morphology revealed that green-mediated GIC displays smoother surface characteristics in contrast to conventional GIC. These results underscore the potential advantages of utilizing green-mediated nanocomposite-modified GIC in dental applications, suggesting enhanced mechanical properties and surface quality over conventional.

Evaluation of the Effect of Nanographene Oxide on Microleakage of Conventional and Resin-Modified Glass Ionomer

Objectives

One of the important features of the restorative materials is the ability to seal and prevent the microleakage. Glass ionomer cement (GIC) still exhibits some microleakage despite establishing a chemical bond to the tooth. The aim of this study was to evaluate the effect of nanographene oxide (nGO) on the microleakage of conventional (CGIC) and resin-modified glass ionomer cement (RMGIC).

Methods

Thirty intact extracted molars were used. Class V cavities were prepared on their buccal and lingual surfaces. The samples randomly divided into two main groups of CGIC and RMGIC; each of them was randomly subdivided into three subgroups, including the group without nGO (control), the group with 1% nGO, and the group with 2% nGO. After restoring the cavities, they were subjected to thermocycling (1,000 cycles at 5/55°C). Two percent basic fuchsin solution was used to perform the microleakage test, and then the sectioned samples were examined by a stereomicroscope 40x. Kruskal-Wallis test, Dunn's test, and Mann-Whitney U test were used to analyze the data (P < 0.05).

Results

Group CGIC + 1% nGO at the gingival margin and group RMGIC + 1% nGO at both gingival and occlusal margins had significantly less microleakage than their control groups (P=0.008, P=0.002, P=0.023, respectively). Also, in these two groups, there were no significant differences between the microleakage of the occlusal and gingival margins (P=0.132, P=0.511, respectively), while in all other groups, the gingival microleakage was significantly higher than that of occlusal microleakage.

Conclusions

The addition of 1% nGO significantly reduced the gingival microleakage of CGIC and the occlusal and the gingival microleakage of RMGIC, while the addition of 2% nGO did not cause a significant reduction in microleakage.

Evaluation of the effect of nano-graphene oxide on shear bond strength of conventional and resin-modified glass ionomer cement

OBJECTIVES

Recently, nano-graphene oxide (nGO), a material with unique mechanical properties, has been introduced to improve the properties of glass ionomer cement (GIC). The purpose of this study was to investigate the effect of adding nGO on the shear bond strength (SBS) of conventional (CGIC) and resin-modified GIC (RMGIC).

METHODS

Sixty intact molars were mounted and their occlusal surface was cut at a depth of 1 mm below the dentinoenamel junction. 1 wt.% and 2 wt.% of nGO (US Research Nanomaterials, Inc.) were added to CGIC and RMGIC (GC Corporation). The samples were randomly divided into six groups (n = 10), including 1: CGIC,  2: CGIC + 1% GO, 3: CGIC + 2% GO, 4: RMGIC, 5: RMGIC + 1% GO, and 6: RMGIC + 2% GO. Plastic molds were placed on the surface of the dentin pretreated with 10% polyacrylic acid (GC Corporation) and filled with prepared cement according to the manufacturer's instruction. After 24 h of storage in an incubator, the SBS test was done by the universal testing machine. Data were analyzed using two-way analysis of variance and post hoc Tukey tests (p < .05).

RESULTS

In the group of CGIC, mean SBS was significantly lower than all other study groups (p < .001), and groups 5 (RMGIC + 1% GO) and 6 (RMGIC + 2% GO) showed significantly higher values compared to all other study groups (p < .001). However, the difference between groups 2 and 3, as well as the difference between groups 5 and 6, was not significant (p = .999 andp = .994, respectively). RMGI groups had significantly higher SBS than their corresponding CGIC groups.

CONCLUSIONS

The addition of 1% and 2% nGO significantly increased the SBS of CGIC and RMGIC to the dentin, which can be considered as a promising point for wider clinical application of this material.

Evaluation of the Effect of Nanoparticle Graphene Oxide on Flexural Strength of Glass Ionomer Cements

Aim

Glass ionomer (GIC) is a widely used restorative material in dentistry, but it has relatively weak mechanical properties. In this research, the effect of graphene oxide (GO) on the flexural strength of GIC was investigated.

Materials and Methods

In this experimental study, 60 GIC samples in 6 groups of 10 were prepared, including Group 1: control conventional glass ionomer (CGIC), Group 2: CGIC + 1% wt of GO, Group 3: CGIC + 2% wt of GO, Group 4: control resin-modified glass ionomer (RMGI), Group 5: RMGI + 1% wt of GO, and Group 6: RMGI + 2% wt of GO. The samples were kept for 24 hours. The flexural strength of the samples was measured by using a universal testing machine. Data were analyzed by two-way ANOVA and posthoc Tukey test. (P < 0.05).

Results

In the RMGI groups, the mean flexural strength value of the RMGI + 2% GO group was significantly higher than that of the RMGI control group (P=0.027). In the comparison of RMGI groups with their corresponding CGIC groups, the mean flexural strength values of all RMGI groups were significantly more than CGIC groups (P < 0.001). RMGI + 1% GO was not significantly different from control RMGI and RMGI + 2% GO (P=0.802, P=0.395, respectively). There was no significant difference between CGIC groups.

Conclusion

Adding 2% by weight of GO to RMGI increases the flexural strength of RMGI, which could be of great importance in clinical practice in order to reinforce the mechanical properties of this dental material. The flexural strength of RMGI is higher than that of CGIC.

Mechanical Properties and Antibacterial Effect on Mono-Strain of Streptococcus mutans of Orthodontic Cements Reinforced with Chlorhexidine-Modified Nanotubes

Recently, several studies have introduced nanotechnology into the area of dental materials with the aim of improving their properties. The objective of this study is to determine the antibacterial and mechanical properties of type I glass ionomers reinforced with halloysite nanotubes modified with 2% chlorhexidine at concentrations of 5% and 10% relative to the total weight of the powder used to construct each sample. Regarding antibacterial effect, 200 samples were established and distributed into four experimental groups and six control groups (4 +ve and 2 -ve), with 20 samples each. The mechanical properties were evaluated in 270 samples, assessing microhardness (30 samples), compressive strength (120 samples), and setting time (120 samples). The groups were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, and the antibacterial activity of the ionomers was evaluated on Streptococcus mutans for 24 h. The control and positive control groups showed no antibacterial effect, while the experimental group with 5% concentration showed a zone of growth inhibition between 11.35 mm and 11.45 mm, and the group with 10% concentration showed a zone of growth inhibition between 12.50 mm and 13.20 mm. Statistical differences were observed between the experimental groups with 5% and 10% nanotubes. Regarding the mechanical properties, microhardness, and setting time, no statistical difference was found when compared with control groups, while compressive strength showed higher significant values, with ionomers modified with 10% concentration of nanotubes resulting in better compressive strength values. The incorporation of nanotubes at concentrations of 5% and 10% effectively inhibited the presence of S. mutans, particularly when the dose-response relationship was taken into account, with the advantage of maintaining and improving their mechanical properties.