Microhardness Of Glass Ionomer Cement Research Articles

In vitro evaluation of some mechanical properties and fluoride release of glass-ionomer cement modified with seashell nanoparticles.

This research assessed the compressive strength and microhardness of glass-ionomer cement (GIC) after incorporating seashell nanoparticles and evaluated the inert fluoride-releasing ability. Seashell nanoparticles were synthesized by a mechanical grinding protocol. These particles were characterized by transmission electron microscopy and energy dispersive x-ray and added to the glass-ionomer powder in a weight-to-weight ratio. Seventy-five study samples were distributed into eight samples for each study group (control, 5%, and 10% seashell) to have 24 samples for each test of the study (compressive strength, microhardness, and fluoride release). One sample per group was prepared for the Fourier transform infrared spectroscopy (FTIR) test. The fluoride ion release was measured after one and four weeks of incubation period at 37 ºC, while other tests were conducted after 24 hours of incubation. In all the test variables, the 10% seashell group showed the highest significant mean, followed by the 5% seashell and the control group. However, there was no significant difference between the 5% and 10% seashell groups in the first week of fluoride release. According to the results, 10% seashell nanoparticles were the best to improve the mechanical properties of GIC and boost the fluoride-releasing potential.

Analysis of the Porosity and Microhardness of Glass Ionomer Cements

Glass ionomer cements (GICs) are currently the first-choice materials in minimally invasive dentistry and are widely used in paediatric dentistry. The objective of this study was to evaluate the influence of viscosity and mixing on porosity and the relationship between the porosity and microhardness of GICs. Nine GICs were used: EQUIA® Forte Fil, Ionostar®Plus, 3MTMKetacTM Universal AplicapTM, Riva Light Cure HV®, Riva Silver®, Riva Protect®, VitremerTM, VitrebondTM Plus and Activa BioActive RestorativeTM. Samples were prepared from each material and images were obtained by scanning electron microscopy (SEM). Using software, the number and diameter of pores, area, and percentage of area they occupied were measured. After SEM analysis, the samples were used to make surface microhardness (SMH) measurements. Ionostar® Plus, EQUIA® Forte Fil and Riva Light Cure HV® had the highest number of pores. Riva Protect® had the largest pores and the highest percentage of pore-occupied area, while Activa BioActive RestorativeTM and VitrebondTM Plus had a smaller pore size and a smaller percentage by area. Riva Silver® and EQUIA® Forte Fil showed the highest microhardness values and VitrebondTM Plus and VitremerTM the lowest. In conclusion, when the cement viscosity is low, the type of mixture determines the degree of porosity, but has less influence when viscosity is high. There was no correlation between microhardness and the porosity of GICs.

Influence of ultrasonic excitation on microhardness of glass ionomer cement.

Numerous researchers have attempted to improve the mechanical properties of glass ionomer cement since 1972. In this study, ultrasonic curing treatment was introduced during the mixing of glass ionomer cement (GC Fuji IX) to facilitate intimate mixing, compaction and adaptation of residual glass particle which consequently improves densification of the material. To assess the influence of ultrasonic treatment on the microhardness of glass ionomer cement (GC Fuji IX) and compare it with the conventionally cured method. A total of 40 specimens (2 × 2 mm) were fabricated and equally divided into two groups: Group I (conventional curing method) and Group II (ultrasonically cured). For Group II, an ultrasonic scaler was used which provides energy to ensure proper mixing of material without leaving any air bubbles or unmixed particles. Vicker's hardness test was employed to generate the average microhardness values by making three indentations at different points on each specimen. Statistical Package for Social Sciences (SPSS) Version 17 was used, employing independent samples T test to compare the difference in microhardness values between two curing groups. The average surface hardness value for conventional cured GIC was 62.21 ± 13.61 while ultrasonically cured GIC exhibited a higher mean microhardness value of 66.37 ± 12.83. Additionally, the average microhardness values produced by the two groups showed statistically significant differences (p value < 0.035). Ultrasonic excitation treatment leads to intimate mixing and accelerated hardening of glass ionomer cement thereby enhancing its microhardness and reducing early weakness.

Evaluation of compressive strength, shear bond strength, and microhardness values of glass-ionomer cement Type IX and Cention N.

Aim:This study aimed to compare the compressive strength, shear bond strength, and microhardness of glass-ionomer cement (GIC) Type IX and Cention N.Materials and Methods:Five samples each of GIC Type IX and Cention N were prepared for testing the shear bond strength, tensile strength, and microhardness. Cylinders of the samples measuring 1 cm diameter and 6 mm height were prepared for compressive strength and shear bond strength. For shear bond strength, these samples were embedded into acrylic blocks of dimensions 2 cm × 2 cm. Testing of shear bond strength and compressive strength was done by mounting the samples in a universal testing machine with a crosshead speed of 1 mm/min. The samples for microhardness were 1 cm diameter and 5 mm height. The samples were mounted on Vickers microhardness testing machine to test the microhardness.Results:The values for shear bond strength of Cention N were statistically highly significant (P < 0.01) as compared to GIC Type IX, whereas the compressive strength and microhardness values of Cention N were statistically significant (P < 0.5) as compared to GIC Type IX.Conclusion:The results suggest significantly higher values for mechanical properties of Cention N as compared to GIC Type IX.

Analysis of the surface roughness and microhardness of dental restorative materials exposed to heat sources and cold temperatures for human identification purposes

BackgroundFatal accidents involving the action of heat, such as burns, explosions, automobile accidents, and aircraft crashes, among others, or action of cold, such as collisions in snowy locations, severe blizzards, cold waves, earthquakes, and avalanches, are frequent day-to-day occurrences. During post-mortem dental examination of victims, restorative materials such as the composite resin (CR), glass ionomer cement (GIC), and amalgam may be found. The action of the heat or cold on these materials may change their properties. This study aimed to evaluate the changes occurred in the surface roughness and Knoop microhardness of the dental restorative materials of freezing or burnt victims, supporting an adequate comparison with the antemortem data, helping on human identification process.MethodsOne hundred eighty caries-free bovine teeth were prepared and separated into groups, according to the restorative material, temperature, and period for analysis. The surface roughness and microhardness were analyzed by a profilometer and a microhardness tester, before and after the action of the heat (100 °C, 200 °C, 300 °C) and the cold temperatures (2.5 °C, − 20 °C, − 80 °C).ResultsThe results demonstrated that there was no alteration on properties of CR after the heat that caused significant changes in the surface roughness of GIC and amalgam and the microhardness of GIC. The low temperatures produced no significant differences in any of the properties of the restorative materials studied.ConclusionThe surface roughness and Knoop microhardness tests could distinguish the tooth-colored restorative materials irrespective of the action of the heat or cold temperatures.

A comparative evaluation of the microhardness of glass ionomer cements modified with chitosan and chlorhexidine: A 1-year in vitro study

Aims and Objectives: Enhancement of the therapeutic properties of glass ionomer cements with antimicrobials, without alterations in its existing physical properties is of current research interest. One such innate property is microhardness. The aim of this study was to compare the microhardness of chlorhexidine-modified glass ionomer cement (CHX GIC) and chitosan-modified glass ionomer cement (CHT GIC) with an unmodified glass ionomer cement (FUJI IX GIC) and to study the variations in their microhardness when stored for a year. Materials and Methods: In an experimental analytic study, Fuji IX GIC liquid was modified with chitosan to form 10% vol/vol of CHT GIC. Fuji IX GIC powder was modified with chlorhexidine diacetate powder to form 1% wt/wt CHX GIC. Fuji IX GIC was used as control. Forty cylindrical samples each of the control and experimental cements were prepared, embedded in resin and stored in distilled water. Vickers microhardness testing was performed at stipulated time periods. The mean and standard deviation of each group were calculated. The data were analyzed using analysis of variance and post hoc Tukey test for multiple comparisons. Results: Materials showed significant difference in microhardness (P <0.000) at all time periods chosen for the study. FUJI IX GIC had the highest microhardness values at all time periods. CHT GIC showed the lowest microhardness and CHX GIC showed excellent stability over time. Conclusion: Although the therapeutic effects of modified GICs are proven, these additives can significantly and negatively alter the existing microhardness of the parent material.

Effect of addition of chitosan on water sorption, solubility and microhardness of glass ionomer cement

Background A glass ionomer cement (GIC) restorative materials is commonly used in dentistry for permanent cementation of indirect restorations, liner, base or as atraumatic restorative treatment for the restoration of primary teeth, especially in developing countries. Water sorption and solubility of dental cement could be a primary cause of restoration failure. Early moisture contamination on luting cements during setting results not only in an increased loss of substance but also a reduction of physical properties especially its surface hardness. Chitosan can improve the mechanical properties of GICs and decrease its solubility, therefore it is necessary to do research on the solubility, water sorption and surface hardness of the chitosan modified GICs. Aim This study was aimed to investigate the effect of addition of chitosan to the liquid of GIC on water sorption, solubility and microhardness of GIC. Materials and methods Commercially available powder/liquid restorative GIC was used in this study. A total of 60 samples were used in this study. The GIC samples was divided into samples of conventional GIC as a control (group I), GIC modified with 25% (v/v) chitosan solution (group II) and GIC modified with 50% (v/v) chitosan solution (group III). Water sorption and solubility results obtained from the difference between the weights of samples before and after immersion in an incubator and after dehydration. The samples with 6 mm diameter and 3 mm thickness were used for Vickers microhardness test. Results were subjected to analysis of variance and Tukey's test. Results The addition of chitosan to GIC may increase water sorption of GIC and decreased its solubility. The addition of chitosan to GIC significantly decreased its surface hardness. Conclusion The modification of GIC liquid with chitosan showed to be more effective in decreasing the solubility of GIC. However, the microhardness may significantly decrease with chitosan incorporation in polyacrylic acid liquid.

Influence of Thermo-Light Curing with Dental Light-Curing Units on the Microhardness of Glass-Ionomer Cements.

The purpose of this study was to verify for various glass-ionomer cement (GIC) products whether the application of thermo-light curing on the initial curing material produces an increase in microhardness, and to determine whether this hardness varies depending on the depths of the GIC samples. The efficacy of various polymerization units on this additional hardening was also examined. The GIC samples were thermo-light cured for 60 seconds with three polymerization units. The Vickers microhardness was measured at three different depths: 2 mm, 3 mm, and 4 mm. Analysis of variance and Newman-Keuls test showed statistically significant differences among tested samples for all three GIC groups (P < .001). The results of linear regression analysis showed a statistically significant relationship between the hardness of the material and the temperature for samples with depths of 2 mm (R = 0.78; P = .0028) and 3 mm (R = 0.59; P = .045). The findings of this study indicate that thermo-light curing of GIC with different polymerization units for 60 seconds during setting reaction increases the microhardness of the GICs at all depths tested and may increase resistance to mastication forces, which can be validated in future clinical studies.

The Effect of Heat Application on Microhardness of Glass Ionomer Cement and on Pulp Temperature-What to Use in the Clinic

Abstract Objectives: To examine the effect of energy application on microhardness of glass-ionomer cement (GIC), and the effect of the temperature applied on pulp temperature, in vitro and in vivo. Methods: Discs of EQUIA (GC Co. Japan) were examined for microhardness using Vickers indentations after heat application of 50 or 60oC for 30 or 60 seconds using light curing devices or a specific heating device, and compared to self setting GIC. The measurements were performed after 30, 60 minutes and after 5 days. Heat was applied to GIC occlusal restorations in deciduous and permanent teeth both in vitro and in vivo and the effect on pulp temperature was measured using a thermo-coupling device. Results: The best microhardness results were observed using a specific heating device at 50oC for 30 or 60 seconds, and the differences to self setting material after 60 minutes were statistically significant. After 5 days the differences in microhardness were non-significant. Temperature of 60oC caused the pulp temperature to rise with more than the accepted 5.5oC and may cause irreversible damage to the pulp. Similar pulpal temperature changes were observed in vitro and in vivo in deciduous and permanent teeth. Significance: The application of heat energy to GIC using a heating device improved the surface microhardness significantly during the first 60 minutes. The temperature to be used is around 50oC for 30 or 60 seconds in order not to cause irreversible damage to the pulp.

Effect of acidulated phosphate fluoride application on microhardness of glass ionomer cement

Introduction: Acidulated phosphate fluoride (APF) gels are commonly used as preventive caries materials in paediatric dentistry while glass ionomer cements (GICs) are widely used as a restorative material. The purpose of this study was to determine the effect of acidulated phosphate fluoride application towards the microhardness of GIC. Methods: This study was an experimental laboratory study where ten specimens were prepared from high viscosity GIC, which was Fuji IX. Specimens were stored in 50 ml distilled water at first 24 hours at 37°C, and then specimens were divided into fluoride group which was immersed in 25 ml of 1.23 % APF gel and control group which was stored 25 ml distilled water for 24 hours at 37°C. The Micromet II Microhardness Tester, Buehler, IL, USA that was standardised for Vickers hardness test was used to test the specimens at 100-gram load. Data were analysed using the t-test comparison test. Results: The level of microhardness of the fluoride group (14.34) was much lower compared to the control group (43.21) with a highly significant difference (p&lt;0.01). Conclusion: The application of 1.23% APF gel on high viscosity GIC reduces the microhardness level compared to the control group.

Evaluation of Fluoride Release, pH and Microhardness of Glass Ionomer Cements

Objective: To evaluate fluoride release, pH and microhardness of glass ionomer cements (GIC). Material and Methods: Four different cements: Vidrion ® R (G1), Vitro Fil ® (G2), Maxxion ® (G3) and Magic Glass ® (G4) and a composite resin (G5 - control group) comprised the sample. Thirty specimens were manufactured (10 mm x 3 mm) and stored in deionized water. Analyses were performed after 24 hours, 7 days and 28 days. The following devices were used for measurements: fluorometer, pH meter and microhardness tester. Data were analyzed by Kruskal-Wallis, Mann-Whitney, Friedman and Wilcoxon tests (α = 0.05) using the SPSS ® software (Statistical Package for Social Sciences) version 17. Results: GICs were able to release fluoride; however, the amount released decreased with increasing immersion time (p <0.002). The pH of all products increased over time, the lowest value was identified for Magic Glass (5.93) and the highest for Maxxion (6.94) at time of 24 h. Materials showed significant decrease in surface microhardness, especially G4 for presenting the lowest recorded values (p <0.05). Conclusion: GICs are fluoride-releasing restorative materials with pH favorable to oral homeostasis and good mechanical behavior.

Effectiveness of commonly available surface protecting agents in maintaining microhardness of two cements.

To estimate the microhardness of glass ionomer cement (vitrofil) and resin modified glass ionomer cement (vitremere) in the presence and absence of different surface protections. An in-vitro experimental study. The Department of Operative Dentistry, Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences and the Department of Material Sciences, NED University, Karachi, from August 2011 to January 2012. Seventy-two discs of each material were made in polytetrafluoroethylene mold which was 10 mm in diameter and 2 mm in thickness. Four groups were made for each material containing 18 discs; G1/G5 (control group), G2/G6 (solid petroleum jelly), G3/G7 vernal (resin varnish), G4/G8 (nail varnish). After initial setting reaction surface protection was applied to discs. Once the surface protection was dried, discs were stored in deionized water at 37°C for 24 hours. After 24 hours, the discs were polished. Microhardness test were performed in digital microhardness tester. The results were statistically analyzed with the help of two-way ANOVA. For glass ionomer cement the only G4 (nail varnish) differed from the G1 (control group) [p < 0.05], No significant difference was seen with other surface protection agents. For resin modified glass ionomer cement, the G7 (resin varnish) and G8 (nail varnish) gave better result from the G5 (control group). Nail varnish and resin varnish showed better surface protection for GIC and RMGIC. The presence of toluene in nail varnish have harmful effects so should not be preferred if resin varnish is available.

Comparative evaluation of the remineralising effects and surface microhardness of glass ionomer cement containing grape seed extract and casein phosphopeptide — amorphous calcium phosphate: an in vitro study

To evaluate and compare in vitro the remineralising effects and surface microhardness of glass ionomer cement (GIC), GIC containing grape seed extract and GIC containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). An in vitro study with 45 mandibular premolars with standardised class V cavities prepared on the buccal and lingual surfaces. Artificial caries-like lesions were created and teeth were randomly divided into 3 groups of 15 teeth each. Each tooth was sectioned longitudinally into buccal and lingual halves; lingual half was used as control and the other as the test specimen. Axial longitudinal sections of the control specimens were analysed under polarised light microscopy. The experimental halves were restored with 3 materials. Group I: glass ionomer cement (GIC), Group II: 10% (w/w) grape seed extract and GIC (GSGIC), Group III: 10% (w/w) casein phosphopeptide-amorphous calcium phosphate (Recaldent) and GIC (CPPGIC). The restored tooth specimens were exposed to pH cycling for 28 days and analysed again for remineralisation under polarised microscopy. For the second part of the study, 60 cylindrical specimens (20 each) were made using standardised brass moulds and the three experimental materials. The specimens were immersed individually in de-ionised water. After 7 days of immersion, 10 specimens from each group were subjected to microhardness measurements and repeated on the remaining specimens at the end of 30 days. One way ANOVA and post-hoc Tukey's test were used for statistical analysis. CPPGIC showed the greatest remineralisation followed by GSGIC and least for GIC. Comparisons of microhardness between the three groups were not statistically significant. Grape seed extract and CPPACP can be used for remineralisation of damaged dentine and their incorporation into GIC does not compromise the microhardness properties significantly.

Comparative Evaluation of the Remineralizing Effects and Surface Micro hardness of Glass Ionomer Cements Containing Bioactive Glass (S53P4):An in vitro Study.

ABSTRACTDental cements including the glass ionomer cement (GIC) have found widespread use in restoring tooth structures. In this study, modifications of glass ionomer cements (GICs) were made by adding bioactive glass (BAG) to GIC to obtain bioactive restorative materials. This study used polarized light microscopy (PLM) to examine the remineralization effects of the study materials on dentin. It also evaluated the Vickers microhardness of the experimental materials. Experimental glass ionomer cement (GIC)-BAG materials were made by mixing 10 wt% of BAG particles with conventional cure and resin-modified GIC powders. Class V restorations were made in 80 extracted mandibular teeth which included 4 groups of 20 teeth each. 100 |jm sections of the teeth were examined under polarized light microscope after undergoing pH cycling. Materials were also processed into 80 cylindrical specimens and immersed in water for 7 and 30 days before mechanical tests. Resin-modified GIC containing BAG showed a thick uniform layer of mineralization on the restoration-dentin interface. The conventional cure GIC-based materials had higher surface microhardness than the resin-modified materials.Significance: The addition of BAG to GIC compromises the mechanical properties of the materials to some extent. Thus, their clinical use ought to be restricted to applications where their bioactivity can be beneficial, such as root surface fillings and liners in dentistry.

Evaluation of the effect of tracer pH on the sealing ability of glass ionomer cement and mineral trioxide aggregate

The aim of this study was to evaluate the sealing ability and physical and chemical properties of glass ionomer cement (GIC) and mineral trioxide aggregate (MTA) using Rhodamine B at different pHs as tracer. Chemical analysis, pH and micro-hardness of GIC and MTA were performed. In addition dye leakage was assessed by tracer leakage using Tandem Scanning Confocal Microscope (TSM) after immersion of premolar teeth in a stock and a buffered fluorescent Rhodamine B for 24 h. Ultra-structural changes within the materials were evaluated by viewing under the field emission scanning electron microscope (FESEM). GIC and MTA showed elemental peaks for silicon, aluminium and calcium while MTA also had bismuth. GIC was acidic (P = 0.001) and caused an increase in dye pH (P = 0). Immersion of MTA in any of the test solutions resulted in an increase in the pH of the solution (P < 0.05). Use of a dye solution of lower pH than the material under test increased the cement micro-hardness. GIC demonstrated marginal leakage on TSM and both increase in marginal leakage and material porosity on FESEM. MTA was not affected by the use of acidic dye but showed a tendency to take up dye within the material shown on TSM. Evaluation of marginal adaptation of dental materials was shown to be dependent on the technique used for viewing the material to tooth interface, the properties of the material under study and the pH of the dye used.

Mechanical and Fluoride Release Properties of Titanium Tetrafluoride-added Glass-ionomer Cement

The aim of this study was to determine the fluoride-release and mechanical properties of a water-hardening glass-ionomer cement (GIC) (ChemFil Superior) when titanium tetrafluoride (TiF4) was added. Three experimental groups were prepared with TiF4 added to the liquid component of the material in concentrations of 0.5, 1, and 2%. The control group was the original form of the cement and free of TiF4. After the specimens (4 mm in diameter x 6 mm in length) were prepared, their compressive strength, microhardness, modulus of elasticity, and fluoride release were measured. Data were analyzed using one-way analysis of variance (ANOVA) and post-hoc test (Bonferroni/Dunn correction). The addition of TiF4 into GIC significantly reduced fluoride release from the material with the exception of 1% TiF4 (p < 0.0083). Compressive strengths of 0.5 and 1% TiF4-added GICs were higher than that of the original GIC, but it was not statistically significant (p > 0.05). The differences among modulus of elasticity values of experimental and control groups were not significant (p > 0.05). Similarly, microhardness of GIC was not affected with TiF4 addition (p > 0.05).

Wear and microhardness of glass-ionomer cements.

Pin-and-disc wear and Knoop Hardness measurements were made on three commercial glass-ionomer cements having slightly different compositions. The specific objective was to determine whether these cements have potential for use in posterior teeth, and, if not, what modifications in composition and structure would be appropriate to enhance their performance. The specimens were pre-conditioned in air, water, or lactic acid at 37 degrees C for one week prior to being wear-tested. Although differences among the samples were noted, some common trends were observed. From changes in hardness, before and after storage, two opposing trends were observed. One trend involved continued cross-linking and possible dehydration, resulting in a substantial increase in hardness. The other trend involved softening from penetrant liquid absorption and a concomitant decrease in hardness. The wear resistances compared favorably with those for resin-based composites except for the lactic-acid-stored specimens, for which changes in microstructure were revealed by SEM. All specimens were very brittle, and catastrophic failure during wear was frequent. Although our conclusion is that glass-ionomer cements with composition similar to those evaluated here are not acceptable for posterior occlusal application, some compositional changes may enhance their performance in stress-bearing applications.