Hollow glass fibers in reinforcing glass ionomer cements

Effect of E-glass fibers addition on compressive strength, flexural strength, hardness, and solubility of glass ionomer based cement

BACKGROUND

In dentistry, glass-ionomer cements (GICs) are extensively used for a range of applications. The unique properties of GIC include fluoride ion release and recharge, chemical bonding to the tooth's hard tissues, biocompatibility, a thermal expansion coefficient like that of enamel and dentin, and acceptable aesthetics. Their high solubility and poor mechanical qualities are among their limitations. E-glass fibers are generally utilized to reinforce the polymer matrix and are identified by their higher silica content.

OBJECTIVES

The purpose of the study was to assess the impact of adding (10 wt% and 20 wt%) silane-treated E-glass fibers to traditional GIC on its mechanical properties (compressive strength, flexural strength, and surface hardness) and solubility.

METHODS

The characterization of the E-glass fiber fillers was achieved by XRF, SEM, and PSD. The specimens were prepared by adding the E-glass fiber fillers to the traditional GIC at 10% and 20% by weight, forming two innovative groups, and compared with the unmodified GIC (control group). The physical properties (film thickness and initial setting time) were examined to confirm operability after mixing. The evaluation of the reinforced GIC was performed by assessing the compressive strength, flexural strength, hardness, and solubility (n = 10 specimens per test). A one-way ANOVA and Tukey tests were performed for statistical analysis (p ≤ 0.05).

RESULTS

The traditional GIC showed the least compressive strength, flexural strength, hardness, and highest solubility. While the GIC reinforced with 20 wt% E-glass fibers showed the highest compressive strength, flexural strength, hardness, and least solubility. Meanwhile, GIC reinforced with 10 wt% showed intermediate results (P ≤ 0.05).

CONCLUSION

Using 20 wt% E-glass fiber as a filler with the traditional GIC provides a strengthening effect and reduced solubility.

Mechanical Properties and Ion Release from Fibre-Reinforced Glass Ionomer Cement

The aim of this study was to compare the mechanical properties and ion release from a commercially available resin-modified glass ionomer cement to a formulation reinforced by the addition of short glass fibres at various percentages. Methods: Three experimental groups were prepared by adding a mass ratio of 10%, 15% and 20% of short glass fibres to the powder portion of the cement from a capsule (GC Fuji II LC), while the control group contained no fibres. Microhardness (n = 12), fracture toughness, and flexural, compressive and diametral tensile strength (n = 8) were evaluated. To study ion release, readings were obtained utilising fluoro-selective and calcium-selective electrodes after 24 h, 7 days and 30 days (n = 12). The spatial distribution of fibres within the material was evaluated through scanning electron microscopy. The data were analysed using one-way ANOVA with a Bonferroni adjustment. Results: The findings suggest that elevating fibre weight ratios to 20 wt% results in improved mechanical properties (p < 0.05) in microhardness, flexural strength, diametral tensile strength and fracture toughness. In terms of ion release, a statistically significant difference (p < 0.001) was observed between the groups at the conclusion of 24 h and 7 days, when the fluoride release was much higher in the control group. However, after 30 days, no significant distinction among the groups was identified (p > 0.05). Regarding calcium release, no statistically significant differences were observed among the groups at any of the evaluated time points (p > 0.05). SEM showed the fibres were homogeneously incorporated into the cement in all experimental groups. Conclusions: Resin-modified glass ionomer enhanced with short glass fibres at a weight loading of 20% showcased the most favourable mechanical properties while concurrently maintaining the ability to release fluoride and calcium after a 30-day period.

Modifying dental composites to formulate novel methacrylate-based bone cements with improved polymerisation kinetics, and mechanical properties

OBJECTIVES

The aim was to develop bone composites with similar working times, faster polymerisation and higher final conversion in comparison to Cortoss™. Additionally, low shrinkage/heat generation and improved short and longer-term mechanical properties are desirable.

METHODS

Four urethane dimethacrylate based composites were prepared using tri-ethylene-glycol dimethacrylate (TEGDMA) or polypropylene dimethacrylate (PPGDMA) diluent and 0 or 20 wt% fibres in the glass filler particles. FTIR was used to determine reaction kinetics, final degrees of conversions, and polymerisation shrinkage/heat generation at 37 °C. Biaxial flexural strength, Young's modulus and compressive strength were evaluated after 1 or 30 days in water.

RESULTS

Experimental materials all had similar inhibition times to Cortoss™ (140 s) but subsequent maximum polymerisation rate was more than doubled. Average experimental composite final conversion (76%) was higher than that of Cortoss™ (58%) but with less heat generation and shrinkage. Replacement of TEGDMA by PPGDMA gave higher polymerisation rates and conversions while reducing shrinkage. Early and aged flexural strengths of Cortoss™ were 93 and 45 MPa respectively. Corresponding compressive strengths were 164 and 99 MPa. Early and lagged experimental composite flexural strengths were 164-186 and 240-274 MPa whilst compressive strengths were 240-274 MPa and 226-261 MPa. Young's modulus for Cortoss™ was 3.3 and 2.2 GPa at 1 day and 1 month. Experimental material values were 3.4-4.8 and 3.0-4.1 GPa, respectively. PPGDMA and fibres marginally reduced strength but caused greater reduction in modulus. Fibres also made the composites quasi-ductile instead of brittle.

SIGNIFICANCE

The improved setting and higher strengths of the experimental materials compared to Cortoss™, could reduce monomer leakage from the injection site and material fracture, respectively. Lowering modulus may reduce stress shielding whilst quasi-ductile properties may improve fracture tolerance. The modified dental composites could therefore be a promising approach for future bone cements.

Using Functionalized Micron-Sized Glass Fibres for the Synergistic Effect of Glass Ionomer on Luting Material

This laboratory experiment was conducted with the objective of augmenting the mechanical properties of glass ionomer cement (GIC) via altering the composition of GIC luting powder through the introduction of micron-sized silanized glass fibres (GFs). Experimental GICs were prepared through the addition of two concentrations of GFs (0.5% and 1.0% by weight) to the powder of commercially available GIC luting materials. The effect of GF in set GIC was internally evaluated using micro-CT while the mechanical attributes such as nano hardness (nH), elastic modulus (EM), compressive strength (CS), and diametral tensile strength (DTS) were gauged. Additionally, the physical properties such as water solubility and sorption, contact angle (CA), and film thickness were evaluated. Reinforced Ketac Cem Radiopaque (KCR) GIC with 0.5 wt.% GF achieved improved nH, EM, CS, and DTS without affecting the film thickness, CA or internal porosity of the set GIC cement. In contrast, both GF-GIC formulations of Medicem (MC) GIC showed the detrimental effect of the GF incorporation. Reinforcing KCR GIC with 0.5 wt.% silanized GFs could improve the physical and mechanical attributes of luting material. Silanized GF, with optimal concentration within the GIC powder, can be used as a functional additive in KCR GIC with promising results.

Concept of a Novel Glass Ionomer Restorative Material with Improved Mechanical Properties

The objective of this study was to transfer the concept of ductile particle reinforcement to restorative dentistry and to introduce an innovative glass ionomer material that is based on the dispersion of PEG-PU micelles. It was hypothesized that reinforcing a conventional glass ionomer in this way increases the flexural strength and fracture toughness of the material. Flexural strength and fracture toughness tests were performed with the novel reinforced and a control glass ionomer material (DMG, Hamburg, Germany) to investigate the influence of the dispersed micelles on the mechanical performance. Transmission electron microscopy was used to identify the dispersed micelles. Fracture toughness and flexural strength were measured in a 3-point-bending setup using a universal testing machine. Before performing both tests, the specimens were stored in water at 37 °C for 23 h. The fracture toughness (MPa∙m0.5) of the novel glass ionomer material (median: 0.92, IQR: 0.89-0.94) was significantly higher than that of the control material (0.77, 0.75-0.86, p = 0.0078). Significant differences were also found in the flexural strength (MPa) between the reinforced (49.7, 45.2-57.8) and control material (41.8, 40.6-43.5, p = 0.0011). Reinforcing a conventional glass ionomer with PEG-PU micelles improved the mechanical properties and may expand clinical applicability of this material class in restorative dentistry.

Reinforcement of resin-modified glass-ionomer cement with glass fiber and graphene oxide

OBJECTIVE

To evaluate the effect of adding glass fiber and graphene oxide to a resin-modified glass ionomer cement (RMGIC).

METHODS

Experimental RMGICs were prepared by adding separately and simultaneously glass fibers (5, 10, and 20 wt%) and graphene oxide (1, 3, and 5 wt%) to the powder of RMGIC with different ratios. The samples were examined under SEM and XRD. The surface roughness, flexural strength, Vickers microhardness, water sorption, and solubility were investigated. Data were analyzed using ANOVA and Tukey tests (p = 0.05).

RESULTS

Adding fiber and graphene oxide to RMCIS increased the surface roughness, flexural strength, and microhardness. The highest surface roughness value was obtained in the 20% fiber+5% graphene oxide adding group and the lowest in the control group (p < 0.05). The highest microhardness and flexural strength values were acquired in the 20% fiber-adding group and the lowest in the control group (p < 0.05). 10% and 20% fiber addition increased water sorption and solubility (p < 0.05). Adding 3%, 5% graphene oxide, and 20% fiber+5% graphene oxide reduced water sorption (p < 0.05). The highest water sorption was found in the 20% fiber-adding group and the lowest in the 5% graphene oxide and %20 fiber+5% graphene oxide-adding groups (p < 0.05). Graphene oxide alone and together with fiber did not affect the solubility (p > 0.05).

CONCLUSION

The results show that reinforcement of RMGIC with glass fiber and graphene oxide may improve the mechanical properties. But the glass fibers may cause more water sorption and solubility. Graphene oxide may decrease water sorption of RMGIC and fiber-reinforced RMGIC.

Biomimetic approaches and materials in restorative and regenerative dentistry: review article

Biomimetics is a branch of science that explores the technical beauty of nature. The concept of biomimetics has been brilliantly applied in famous applications such as the design of the Eiffel Tower that has been inspired from the trabecular structure of bone. In dentistry, the purpose of using biomimetic concepts and protocols is to conserve tooth structure and vitality, increase the longevity of restorative dental treatments, and eliminate future retreatment cycles. Biomimetic dental materials are inherently biocompatible with excellent physico-chemical properties. They have been successfully applied in different dental fields with the advantages of enhanced strength, sealing, regenerative and antibacterial abilities. Moreover, many biomimetic materials were proven to overcome significant limitations of earlier available generation counterpart. Therefore, this review aims to spot the light on some recent developments in the emerging field of biomimetics especially in restorative and regenerative dentistry. Different approaches of restoration, remineralisation and regeneration of teeth are also discussed in this review. In addition, various biomimetic dental restorative materials and tissue engineering materials are discussed.

A Comprehensive Review of Self-Healing Polymer, Metal, and Ceramic Matrix Composites and Their Modeling Aspects for Aerospace Applications

Composites can be divided into three groups based on their matrix materials, namely polymer, metal and ceramic. Composite materials fail due to micro cracks. Repairing is complex and almost impossible if cracks appear on the surface and interior, which minimizes reliability and material life. In order to save the material from failure and prolong its lifetime without compromising mechanical properties, self-healing is one of the emerging and best techniques. The studies to address the advantages and challenges of self-healing properties of different matrix materials are very limited; however, this review addresses all three different groups of composites. Self-healing composites are fabricated to heal cracks, prevent any obstructed failure, and improve the lifetime of structures. They can self-diagnose their structure after being affected by external forces and repair damages and cracks to a certain degree. This review aims to provide information on the recent developments and prospects of self-healing composites and their applications in various fields such as aerospace, automobiles etc. Fabrication and characterization techniques as well as intrinsic and extrinsic self-healing techniques are discussed based on the latest achievements, including microcapsule embedment, fibers embedment, and vascular networks self-healing.

Evaluation of the Mechanical Properties of Three Resin-Modified Glass-Ionomer Materials

This study is aimed at evaluating the flexural strength (FS), fracture toughness (FT), and diametral tensile strength (DTS) of three resin-modified glass-ionomer cements (RMGICs): Ketac Nano, Riva Light Cure, and Fuji II LC. One hundred twenty specimens were prepared from the RMGIC materials ( $n=10$ ). The cements were mixed and inserted into different mould sizes according to the test performed: FS: rectangular Teflon mould ( $32\text{mm}\times 3.15\text{mm}\times 2\text{mm}$ ); FT: notchless triangular prism (NTP) Teflon mould ( $6\text{mm}\times 6\text{mm}\times 6\text{mm}\times 12\text{mm}$ ); and DTS: ring road stainless steel mould ( $6\text{mm}\times 3\text{mm}$ ). Specimens were light cured for 20 seconds on each surface and stored in distilled water at ${37}^{°}\text{C}\pm 2^{°}\text{C}$ for seven days prior to tests. To evaluate the influence of storage in the mechanical properties of the RMGIs, specimens tested for DTS were stored in distilled water at ${37}^{°}\text{C}\pm 2^{°}\text{C}$ for 32 days prior to test. Data were analyzed by ANOVA and Tukey’s test ( $\alpha =0.05$ ). Fuji II LC presented significantly higher values for all tests employed when compared to Ketac Nano and Riva LC RMGIs. There was no significant difference on DTS before and after the 32-day storage for each material. Fuji II LC presented superior mechanical properties when compared to Ketac Nano, and Riva LC storage showed no influence on the mechanical properties of the RMGI materials tested.

Preparation of basalt fibers grafted with amine terminated urea-based oligomer and its application in reinforcing conventional glass ionomer cement

The purpose of this study was to improve interfacial interaction between basalt fibers (BF) and glass ionomer cement (GIC) matrix with grafting amine terminated urea-based oligomer (DIEDA) onto the surface of BF. The DIEDA-BF was prepared by the reaction between 3-aminopropyl- triethoxysilane (APS) modified BF with Isophorone diisocyanate (IPDI) and followed with ethylenediamine (EDA). The reaction was repeated to obtain three generations of DIEDA-BF which were marked as DIEDA-BF-G₁, DIEDA-BF-G₂, and DIEDA-BF-G₃, respectively. X-ray photoelectron spectroscopy (XPS) was used to characterize DIEDA-BF. 3D morphology analysis was taken to investigate the variation of BF after being treated with EDA. Three-point bending-test, compressive strength (CS) test, and fracture toughness (FT) were used to evaluate the reinforcement effect of DIEDA-BF on commercial GIC (GC Fuji IX). Water sorption (WS) and solubility (SL) were measured according to the mass variation at fixed time intervals. The changes of flexural strength (FS) and modulus (FM) after water immersion were used to evaluate the water-aging resistance of DIEDA-BF reinforced GIC. Pure GIC and APS reinforced GIC (APS-GIC) were used as double control groups. The XPS analysis indicated that DIEDA was successfully grafted onto the surface of BF. 3D morphology analysis revealed that BF could be corroded in EDA, thus DIEDA-BF-G₃ had lower N content on the surface than DIEDA-BF-G₂. The results of mechanical tests showed that DIEDA-BF-G₁ and DIEDA-BF-G₂ had the best reinforcement effect. The DIEDA-BF-G₁ reinforcement GIC (DIEDA-BF-G₁-GIC) was chosen for WS, SL, and water aging resistance test further. The results showed that all fiber reinforced GICs had higher WS than pure GIC, and the relationship in SL between fiber reinforced GICs and pure GIC varied with immersion time. The FS of DIEDA-BF-G₁-GIC decreased after one week of water immersion, and had no variation after prolonging the immersion time. After three months of water immersion, DIEDA-BF-G₁-GIC still had much higher FS than pure GIC and APS-BF-GIC. DIEDA could improve the interfacial interaction between BF and GIC matrix. After long term of water immersion, DIEDA-BF reinforced GIC still had FS higher than 50 MPa, which even met the ISO requirement in FS for dental resin composite. Therefore, GIC/DIEDA modified BF composite had potential to be used in stress bearing areas in dentistry.

Dental Applications of Carbon Nanotubes

Glass ionomer cements and resin-based composites are promising materials in restorative dentistry. However, their limited mechanical properties and the risk of bulk/marginal fracture compromise their lifespan. Intensive research has been conducted to understand and develop new materials that can mimic the functional behavior of the oral cavity. Nanotechnological approaches have emerged to treat oral infections and become a part of scaffolds for tissue regeneration. Carbon nanotubes are promising materials to create multifunctional platforms for dental applications. This review provides a comprehensive survey of and information on the status of this state-of-the-art technology and describes the development of glass ionomers reinforced with carbon nanotubes possessing improved mechanical properties. The applications of carbon nanotubes in drug delivery and tissue engineering for healing infections and lesions of the oral cavity are also described. The review concludes with a summary of the current status and presents a vision of future applications of carbon nanotubes in the practice of dentistry.

The Comparison of Biofilm Formation, Mechanical and Chemical Properties between Glass Ionomer Cement and Giomer

Aims:

The aim of this study was to compare compressive strength and its correlation with the surface morphology and chemical elements of GIC and Giomer, as well as to determine the fluoride amount effect on the bacterial biofilm formation of GIC and Giomer.

Background:

The liability of Glass Ionomer Cement (GIC) mechanical properties is overcome with better antibacterial properties among restorative materials. Another fluoride-releasing restorative material, such as Giomer, has been discovered and is expected to overcome the issues with GIC’s mechanical properties; however, no research has been conducted related to antibacterial properties in Giomer.

Objective:

To compare compressive strength and its correlation with the surface morphology and chemical elements, then determine the fluoride amount effect on the bacterial biofilm formation of GIC and Giomer.

Methods:

Sixteen specimens of GIC and Giomer were prepared for a compressive strength measurement with the Universal Testing Machine. Sixteen specimens of GIC and Giomer were incubated for three days with the Streptococcus mutans culture at 37°C. The bacterial colonization was calculated using the Colony Forming Unit (CFU) and bacterial adhesion was calculated using a Scanning Electron Microscope (SEM). The mechanical properties’ compressive strength measurement, surface morphology, and chemical elements analyses were performed using SEM-EDX.

Results:

The compressive strength of Giomer was higher than GIC (P=0.001). The higher compressive strength of Giomer was reflected by a predominant regular surface, fewer voids, smaller and denser particles, and a higher content of silica and carbon. The bacterial biofilm on the surface of Giomer was higher than GIC, although there was no significant difference. GIC and Giomer have identical chemical elements: C, O, F, Na, Al, Si, P, and Ca.

Conclusion:

The compressive strength of Giomer is better than GIC; however, the biofilm formation of Giomer is higher than GIC, whereas GIC has a higher fluoride content but inferior in surfaces morphology characteristic

Effects of Bacterial Cellulose Nanocrystals on the Mechanical Properties of Resin-Modified Glass Ionomer Cements

OBJECTIVES

 The purpose of this study was to evaluate the effect of bacterial cellulose nanocrystals (BCNCs) on the mechanical properties of resin-modified glass ionomer cements (RMGICs) including compressive strength (CS), diametral tensile strength (DTS), and modulus of elasticity (E).

MATERIALS AND METHODS

 BCNCs were incorporated into RMGIC at various concentrations (0.3, 0.5, and 1 wt%). Unmodified RMGIC was used as the control group. The specimens were stored in distilled water at 37°C for 24 hours. CS and DTS, as well as modulus of elasticity, were evaluated using a universal testing machine. The nanostructure of BCNCs was observed via field emission scanning electron microscopy.

STATISTICAL ANALYSIS

 One-way analysis of variance and post-hoc Tukey tests were used for data analysis. Level of significance was at p < 0.05.

RESULTS

 The addition of BCNCs to RMGIC led to an increase in all of the tested mechanical properties compared with the control group, with a significant increase observed for 1 wt% BCNC. CS and DTS improved up to 23%, and modulus of elasticity increased by 44%.

CONCLUSIONS

 The addition of BCNCs to the RMGIC improved the mechanical properties, including CS, elastic modulus, and DTS. Thus, the newly developed RMGICs with BCNCs might represent an ideal and promising novel dental material in restorative dentistry.

Evaluation of Fracture Toughness, Color Stability, and Sorption Solubility of a Fabricated Novel Glass Ionomer Nano Zirconia-Silica-Hydroxyapatite Hybrid Composite Material

The aim of this study was to investigate the effects of adding a nano zirconia-silica-hydroxyapatite (nanoZrO2-SiO2-HA) composite synthesized using a one-pot sol-gel technique to a conventional glass ionomer cement (GIC), which was then characterized using X-ray diffraction (XRD). Following the characterization studies, further investigations were carried out after the addition of nanoZrO2-SiO2-HA to cGIC (GIC nanoZrO2-SiO2-HA) at various percentages (~5% to 9%) to compare their fracture toughness, color stability, and sorption- solubility in relation to cGIC (Fuji IX). The XRD diffractogram indicated the presence of peaks for ZrO2, SiO2, and HA. The fracture toughness of GIC 5%nanoZrO2-SiO2-HA was statistically higher than that of other percentages of GIC nanoZrO2-SiO2-HA and cGIC. The highest values recorded were fracture toughness ( $1.35\pm 0.15\text{MPa}.{\text{m}}^{1/2}$ ), leading to an increase of ∼57%, as compared to cGIC. Overall, the color change ( $\Delta E$ ) values for GIC 5% nano Zr-Si-HA group were lower than those of cGIC over a one-month period and were between slight and perceptible. In addition, GIC 5%nanoZrO2-SiO2-HA recorded lower sorption values ( $23.64\pm 2.3\mu \text{gm}{\text{m}}^{-3}$ ) as compared to cGIC ( $36.28\pm 2.6\mu \text{gm}{\text{m}}^{-3}$ ) and higher solubility ( $66.46\pm 2.4\mu \text{gm}{\text{m}}^{-3}$ ) as compared to cGIC ( $56.76\pm 1.6\mu \text{gm}{\text{m}}^{-3}$ ). The addition of nanoZrO2-SiO2-HA to cGIC significantly enhanced its physicomechanical properties. Based on the results of our study, GIC nanoZrO2-SiO2-HA has the potential to be suggested as a restorative dental material with diverse applications ranging from cavity restoration, core build-up, and as a luting material.

Mechanical properties and water-aging resistance of glass ionomer cements reinforced with 3-aminopropyltriethoxysilane treated basalt fibers

In order to improve interfacial adhesion between basalt fibers (BF) and glass ionomer cement (GIC) matrix, a silane named 3-aminopropyltriethoxysilane (APS) was used to modify the surface of BF. APS treated BF (APS-BF) was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The influence of APS concentration on mechanical properties of APS-BF reinforced GIC (APS-BF-GIC) was investigated, and water aging resistance of optimum APS-BF-GIC was also studied. The results showed that 5 wt% of APS was the optimum concentration for BF modification, for 5%APS-BF-GIC had the best comprehensive mechanical properties in all of APS-BF-GICs. Though 5%APS-BF-GIC had higher water sorption than BF-GIC and GIC, it still had higher flexural strength and exhibited better water-aging resistance.

Effect on Physical and Mechanical Properties of Conventional Glass Ionomer Luting Cements by Incorporation of All-Ceramic Additives: An In Vitro Study

Introduction

Glass ionomer cements (GICs) are commonly used for cementation of indirect restorations. However, one of their main drawbacks is their inferior mechanical properties.

Aim

Compositional modification of conventional glass ionomer luting cements by incorporating two types of all-ceramic powders in varying concentrations and evaluation of their film thickness, setting time, and strength. Material & Methods. Experimental GICs were prepared by adding different concentrations of two all-ceramic powders (5%, 10, and 15% by weight) to the powder of the glass ionomer luting cements, and their setting time, film thickness, and compressive strength were determined. The Differential Scanning Calorimetry analysis was done to evaluate the kinetics of the setting reaction of the samples. The average particle size of the all-ceramic and glass ionomer powders was determined with the help of a particle size analyzer.

Results

A significant increase in strength was observed in experimental GICs containing 10% all-ceramic powders. The experimental GICs with 5% all-ceramic powders showed no improvement in strength, whereas those containing 15% all-ceramic powders exhibited a marked decrease in strength. Setting time of all experimental GICs progressively increased with increasing concentration of all-ceramic powders. Film thickness of all experimental GICs was much higher than the recommended value for clinical application.

Conclusion

10% concentration of the two all-ceramic powders can be regarded as the optimal concentration for enhancing the glass ionomer luting cements' strength. There was a significant increase in the setting time at this concentration, but it was within the limit specified by ISO 9917–1:2007 specifications for powder/liquid acid-base dental cements. Reducing the particle size of the all-ceramic powders may help in decreasing the film thickness, which is an essential parameter for the clinical performance of any luting cement.

Fiber reinforcement of a resin modified glass ionomer cement

OBJECTIVES

Understand how discontinuous short glass fibers and braided long fibers can be effectively used to reinforce a resin modified glass ionomer cement (RMGIC) for carious lesion restorations.

METHODS

Two control groups (powder/liquid kit and capsule) were prepared from a light cured RMGIC. Either discontinuous short glass fibers or braided polyethylene fiber ribbons were used as a reinforcement both with and without pre-impregnation with resin. For the former case, the matrix was the powder/liquid kit RMGIC, and for the latter case the matrix was the capsule form. Flexural strength was evaluated by three-point beam bending and fracture toughness was evaluated by the single-edge V-notch beam method. Compressive strength tests were performed on cylindrical samples. Results were compared by analysis of variances and Tukey's post-hoc test. Flexural strength data were analyzed using Weibull statistical analysis.

RESULTS

The short fiber reinforced RMGIC both with and without pre-impregnation showed a significant increase of ∼50% in the mean flexural strength and 160-220% higher fracture toughness compared with the powder/liquid RMGIC control. Reinforcement with continuous braided fibers gave more than a 150% increase in flexural strength, and pre-impregnation of the braided fibers with resin resulted in a significant flexural strength increase of more than 300% relative to the capsule control. However, for the short fiber reinforced RMGIC there was no significant benefit of resin pre-impregnation of the fibers. The Weibull modulus for the flexural strength approximately doubled for the fiber reinforced groups compared to the control groups. Finally, compressive strength was similar for all the groups tested.

SIGNIFICANCE

By using a RMGIC as a matrix, higher flexural strength was achieved compared to reported values for short fiber reinforced GICs. Additionally, the short fibers provided effective toughening of the RMGIC matrix by a fiber bridging mechanism. Finally, continuous braided polyethylene fibers gave much higher flexural strength than discontinuous glass fibers, and their effectiveness was enhanced by pre-impregnation of the fibers with resin.

Evaluation of Polypropylene Fiber Reinforced Glass Ionomer Cement: A Comparative In-Vitro Study

Aim:

To compare the surface roughness, microtensile bond strength (µTBS), and flexural strength of polypropylene (PP) fibers reinforced glass ionomer cements (GICs).

Materials and Methods:

A comparative in vitro study was designed to test the PP fiber reinforced GIC, which was formed when 0.5–1 mm length PP fibers were added into the powder of conventional GIC. Four groups were prepared (Group 1: control, Group 2: 1 wt% PP fiber, Group 3: 3 wt% PP fiber, and Group 4: 5 wt% PP fiber) to evaluate flexural strength, surface roughness values, and µTBS. A total of 10 samples with 25 × 2.5 × 5 mm dimensions were prepared for each group to test flexural strength. Disk-shaped specimens ( n = 10) of 2 mm thickness and 10 mm diameter were used to test surface roughness. A total of 24 human primary molar teeth were used to evaluate µTBS, and 12 sticks were obtained for each group. The fractured surface analyses of samples from µTBS was performed using scanning electron microscope. The data obtained from the experiments were recorded and analyzed with one-way analyses of variance technique, and the normality was tested using the Shapiro–Wilk technique. A significance level of .05 was used.

Results:

In flexural strength tests, Group 3 (3 wt% PP fiber) showed significantly increased values ( p < .05) when compared with other groups. Group 4 (5 wt% PP) showed significantly highest values in surface roughness tests ( p < .05). No significant differences were seen between the groups ( p > .05) according to µTBS results. More PP fibers were seen in fractured surfaces, when PP ratio increases.

Conclusion:

It was observed that increased PP fiber percentage showed increased surface roughness, and 3 wt% PP fiber gave optimal values for fracture toughness. Incorporation of PP fiber to GIC does not affect the bonding to primary tooth dentine.

Enhancing the Mechanical Properties of Glass-Ionomer Dental Cements: A Review

This paper reviews the strategies that have been reported in the literature to attempt to reinforce glass-ionomer dental cements, both conventional and resin-modified. These cements are widely used in current clinical practice, but their use is limited to regions where loading is not high. Reinforcement might extend these applications, particularly to the posterior dentition. A variety of strategies have been identified, including the use of fibres, nanoparticles, and larger particle additives. One problem revealed by the literature survey is the limited extent to which researchers have used International Standard test methods. This makes comparison of results very difficult. However, it does seem possible to draw conclusions from this substantial body of work and these are (1) that powders with conventional particle sizes do not reinforce glass-ionomer cements, (2) certain fibres and certain nanoparticles give distinct improvements in strength, and (3) in the case of the nanoparticles these improvements are associated with differences in the morphology of the cement matrix, in particular, a reduction in the porosity. Despite these improvements, none of the developments has yet been translated into clinical use.

Effects of Powdery Cellulose Nanofiber Addition on the Properties of Glass Ionomer Cement

In this study, we aimed to evaluate the effect of the addition of powdery cellulose nanofibers (CNFs) on the mechanical properties of glass ionomer cement (GIC) without negatively affecting its chemical properties. Commercial GIC was reinforced with powdery CNFs (2–8 wt.%) and characterized in terms of flexural strength, compressive strength, diametral tensile strength, and fluoride-ion release properties. Powdery CNFs and samples subjected to flexural strength testing were observed via scanning electron microscopy. CNF incorporation was found to significantly improve the flexural, compressive, and diametral tensile strengths of GIC, and the corresponding composite was shown to contain fibrillar aggregates of nanofibers interspersed in the GIC matrix. No significant differences in fluoride-ion release properties were observed between the control GIC and the CNF-GIC composite. Thus, powdery CNFs were concluded to be a promising GIC reinforcement agent.

Modifications of Glass Ionomer Cement Powder by Addition of Recently Fabricated Nano-Fillers and Their Effect on the Properties: A Review

The aim of this article is to provide a brief insight regarding the recent studies and their recommendations related to the modifications to glass ionomer cement (GIC) powder in order to improve their properties. An electronic search of publications was made from the year 2000 to 2018. The databases included in the current study were EBSCOhost, PubMed, and ScienceDirect. The inclusion criteria for the current study include publication with abstract or full-text articles, original research, reviews or systematic reviews, in vitro, and in vivo studies that were written in English language. Among these only articles published in peer-reviewed journals were included. Articles published in other languages, with no available abstract and related to other nondentistry fields, were excluded. A detailed review of the recent materials used as a filler phase in GIC powder has revealed that not all modifications produce beneficial results. Recent work has demonstrated that modification of GIC powder with nano-particles has many beneficial effects on the properties of the material. This is due to the increase in surface area and surface energy, along with better particle distribution of the nano-particle. Therefore, more focus should be given on nano-particle having greater chemical affinity for GIC matrix as well as the tooth structure that will enhance the physicochemical properties of GIC.

Modification of glass ionomer cements on their physical-mechanical and antimicrobial properties

OBJECTIVE

The aim of this review was to provide an insight about the factors affecting the properties of glass ionomer cements and provides a review regarding studies that are related to modification of glass ionomer cements to improve their properties, particularly on physical-mechanical and antimicrobial activity.

METHODS

PubMed and Science Direct were searched for papers published between the years 1974 and 2018. The search was restricted to articles written in English related to modification of glass ionomer cements. Only articles published in peer-reviewed journals were included. The search included literature reviews, in vitro, and in vivo studies. Articles written in other languages, without available abstracts and those related to other field were excluded. About 198 peer-review articles in the English language were reviewed.

CONCLUSION

Based on the finding, most of the modification has improved physical-mechanical properties of glass ionomer cements. Recently, researchers have attempted to improve their antimicrobial properties. However, the attempts were reported to compromise the physical-mechanical properties of modified glass ionomer cements.

CLINICAL SIGNIFICANCE

As the modification of glass ionomer cement with different material improved the physical-mechanical and antimicrobial properties, it could be used as restorative material for wider application in dentistry.

Effect of discontinuous glass fibers on mechanical properties of glass ionomer cement

Aim: This study investigated the reinforcing effect of discontinuous glass microfibers with various loading fractions on selected mechanical properties of self-cure glass ionomer cement (GIC).

Method: Experimental fiber reinforced GIC (Exp-GIC) was prepared by adding discontinuous glass microfiber (silane/non-silane treated) of 200–300 µm in length to the powder of self-cure GIC (GC Fuji IX) with various mass ratios (15, 20, 25, 35, and 45 mass%) using a high speed mixing device. Flexural strength, flexural modulus, work of fracture, compressive strength and diametral tensile strength were determined for each experimental and control materials. The specimens (n = 8) were wet stored (37 °C for one day) before testing. Scanning electron microscopy equipped with energy dispersive spectrometer was used to analysis the surface of silanized or non-silanized fibers after treated with cement liquid. The results were analyzed with using multivariate analysis of variance MANOVA.

Results: Fiber-reinforced GIC (25 mass%) had significantly higher mechanical performance of flexural modulus (3.8 GPa), flexural strength (48 MPa), and diametral tensile strength (18 MPa) (p < .05) compared to unreinforced material (0.9 GPa, 26 MPa and 8 MPa). No statistical significant difference in tested mechanical properties was recorded between silanized and non-silanized Exp-GIC groups. Compressive strength did not show any significant differences (p > .05) between the fiber-reinforced and unreinforced GIC.

Conclusion: The use of discontinuous glass microfibers with self-cure GIC matrix considerably increased the all of the studied properties except compressive strength.