Cytotoxicity of conventional and modified glass ionomer cements

Various glass ionomer cements (GICs) and resin-modified GICs are widely used as tooth-colored restorative materials. However, their potential effects on pulp tissues are not fully understood. In this study, the authors compared the toxicity of nine types of GICs on cultured human dental pulp cells. Exposure of pulp cells to GICs for five days led to differential growth inhibition as analyzed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Exposure of pulp cells to ProTec CEM, Fuji II LC, Compoglass and GC Lining cement for five days decreased the cell numbers to 11%, 12%, 19% and 25%, respectively, of the control. Exposure of pulp cells to Fuji IX, GIC FX and Fuji II SC also decreased cell numbers by 62%, 33% and 24%, respectively. By contrast, Hy-Bond and Fuji I showed only mild suppression on the growth of pulp cells, with 12% and 16% decreased cell numbers. Morphologically, marked retraction and rounding of pulp cells were noted following exposure to GC Lining cement; in addition, cell surface blebbing was noted following exposure to Compoglass, Fuji II LC and ProTec CEM. Exposure of the pulp cells to Fuji II SC and Fuji IX, however, led to decreases in the cell density, with no obvious morphological changes. These results indicate that resin-modified GICs, such as Compoglass, Fuji II LC, ProTec CEM and GC Lining cements, are more toxic to pulp cells than conventional GICs. It is not recommended that resin-modified GICs be directly applied onto dental pulp cells. However, additional in vivo studies are needed to evaluate the potential toxicities of these resin-modified GICs during clinical operative procedures.     

Nano-cellulose Reinforced Glass Ionomer Restorations: An In Vitro study

ObjectiveVarious modifications in formulation of glass ionomer cements (GICs) have been made in order to improve the clinical performance of these restorations. The aim of this work was to evaluate the microleakage and microshear bond strength (μSBS) of bacterial cellulose nanocrystal (BCNC)–modified glass ionomer cement (GIC) restorations in primary dentition.MethodsA total number of 60 freshly extracted primary molar teeth were selected. Half of the samples were used for μSBS testing (in 2 groups, n = 15). In group 1, conventional GIC (CGIC) of Fuji IX (GC) was placed in cylindrical molds on dentinal surfaces. In group 2, CGIC of Fuji IX containing 1% wt of BCNCs was used. μSBS was evaluated using a universal testing machine. In another part of the study, microleakage of class V restorations was assessed according to the mentioned groups (n = 15). The sectioned samples were observed under stereomicroscope, and microleakage scores were recorded. SPSS version 16.0 (SPSS), independent samples t test, and Mann–Whitney U test were used for statistical analysis at a significance level of P < .05.ResultsResults showed statistically significant differences between the μSBS of CGIC and modified GIC groups (P < .0001). The BCNC-modified GIC group recorded significantly higher bond strength values (3.51 ± 0.033 vs 1.38 ± 0.034 MPa). Also, microleakage scores of CGIC and BCNC-modified GIC restorations were not significantly different (P = .57).ConclusionsBased on our findings, it was concluded that incorporating BCNCs (1% wt) into the CGIC of Fuji IX significantly increased the μSBS to the dentin structure of the primary teeth.     

Dentin bonding of cements. The bonding of cements with dentin in combination with various indirect restorative materials

The number of both luting agents and restorative materials available on the market has rapidly increased. This study compared various types of luting agents when used to bond different indirect, laboratory restorative materials to dentin. Cylinders were produced of six restorative materials (gold alloy, titanium, feldspathic porcelain, leucite-glass ceramic, zirconia, and an indirect resin composite). Following relevant pretreatment, the end surface of the cylinders were luted to ground, human dentin with eight different luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37 °C for one week, the shear bond strength of the specimens was measured and the fracture mode was examined stereo-microscopically. Restorative material and luting agent both had a significant effect on bond strength and there was a significant interaction between the two variables. The zinc phosphate cement and the glass ionomer cements resulted in the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements.     

Crack closure on rehydration of glass-ionomer materials

Moisture-sensitivity of immature glass-ionomer cements suggests that hydration-induced volumetric expansion might close and potentially heal established cracks. Crack closure in glass-ionomer cements (GICs) was observed following rehydration. Circular cavities were prepared in 15 teeth: 10 were restored with resin-modified GICs (5 with Fuji II LC and 5 with Photac-Fil) and 5 were restored with a conventional GIC (Fuji IX); all were dehydrated for 1 min with air and imaged immediately by confocal microscopy. Crack formation in each was located, after which water was placed on the surface and observed for 15 min via a CCD camera. Dehydration caused cracks with measurable gaps, while rehydration resulted in varying degrees of closure: closure was limited in the conventional GIC, and complete or near complete along part/s of the crack in the resin-modified GICs. In all, closure movement became imperceptible after the first 10 min. Statistical analysis indicated no significant difference between the closure behavior of all materials. However, the resin-modified GICs appeared to show a greater potential for closure of established cracks than the conventional GIC upon rehydration.     

Bonding of restorative materials to dentin with various luting agents

The aim was to compare eight types of luting agents when used to bond six indirect, laboratory restorative materials to dentin. Cylinders of the six restorative materials (Esteticor Avenir [gold alloy], Tritan [titanium], NobelRondo [feldspathic porcelain], Finesse All-Ceramic [leucite-glass ceramic], Lava [zirconia], and Sinfony [resin composite]) were ground and air-abraded. Cylinders of feldspathic porcelain and glass ceramic were additionally etched with hydrofluoric acid and were silane-treated. The cylinders were luted to ground human dentin with eight luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], and RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37°C for one week, the shear bond strength of the specimens (n=8/group) was measured, and the fracture mode was stereomicroscopically examined. Bond strength data were analyzed with two-factorial analysis of variance (ANOVA) followed by Newman-Keuls' Multiple Range Test (α=0.05). Both the restorative material and the luting agent had a significant effect on bond strength, and significant interaction was noted between the two variables. Zinc phosphate cement and glass ionomer cements produced the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements. Generally, the fracture mode varied markedly with the restorative material. The luting agents had a bigger influence on bond strength between restorative materials and dentin than was seen with the restorative material.     

How well are GIC product labels related to current systematic review evidence?

Systematic reviews have been recommended as providing the best source of evidence to guide clinical decisions in dentistry. They appraise evidence from trials focused on investigating clinical effects of dental material categories, such as conventional glass-ionomer cements (GIC) or resin-modified GIC. In contrast, the general dental practitioner is introduced to these categories of materials in the form of branded or private product labels that are marketed during dental conventions or through advertisements. Difficulties may arise in recognizing material categories that have been subjected to systematic reviews, because of the multitude of product labels on the current market. Thus, the value and relevance of published systematic review evidence concerning the material categories represented by these labels may remain obscure. Based on a systematic literature search, this article identifies glass-ionomer cement product labels used during clinical trials which, in turn, were subsequently reviewed in systematic review articles (published between 15 April 2009 and 14 April 2011). This article further clarifies how these product labels relate to the systematic review conclusions. The results show that the conventional and resin-modified glass-ionomer cements that were used in most trials were marketed by GC and 3M ESPE, respectively. The conventional GICs used in most of the reviewed trials were Fuji III and Fuji IX, while Vitremer was the most commonly used resin-modified GIC. Evidence from the reviewed trials suggests that GIC provides beneficial effects for preventive and restorative dentistry. However, more trials of higher internal validity are needed in order to confirm (or disprove) these findings. Only GIC products of branded labels and none of private labels were identified, suggesting that private label GIC products have little or no research back-up. CLINICAL RELEVANCE: Dental products, such as glass-ionomers cements (GIC), can only be judged as effective when they are based on sufficient research back-up. Systematic reviews of clinical trials provide such back-up at the highest level. Thus clinicians must be able to identify GIC products for which reliable evidence from systematic reviews of clinical studies is available and know about what such evidence contains.     

Diametral tensile strength and water sorption of glass-ionomer cements used in Atraumatic Restorative Treatment

The purposes of this study were to evaluate the diametral tensile strength and the water sorption of restorative (Fuji IX and Ketac Molar) and resin-modified glass-ionomer luting cements (ProTec Cem, Fuji Plus and Vitremer) mixed at both manufacturer and increased powder: liquid ratio, for their use in the Atraumatic Restorative Treatment. A conventional restorative glass-ionomer (Ketac Fil) was used as control. Specimens (6.0 mm in diameter x 3.0 mm in height) were prepared and stored (1 hour, 1 day and 1 week) for a diametral tensile strength test. Data were subjected to two-way ANOVA and Tukey tests (p<0.05). For the water sorption test, specimens of 15.0 mm in diameter x 0.5 mm in height were prepared and transfered to desiccators until a constant mass was obtained. Then the specimens were immersed in deionized water for 7 days, weighed and reconditioned to a constant mass in desiccators. Data were subjected to one-way ANOVA and Tukey tests (p<0.05). Five specimens of each studied material and consistency were prepared for each test. The resin-modified glass-ionomer cements showed significantly higher strength than the conventional materials. Except for ProTec Cem, the diametral tensile strength of the resin-modified materials significantly increased from luting to restorative consistency. Except for ProTec Cem, the water sorption of the resin-modified glass ionomers was higher than the others. The water sorption of resin-modified materials at restorative consistency was significantly lower than at luting consistency. Resin-modified glass-ionomer luting cements mixed at increased powder: liquid ratio showed better properties than at luting consistency.     

The physical and adhesive properties of dental cements used for atraumatic restorative treatment

Atraumatic Restorative Treatment (ART), a recently reported field dentistry technique, involves removal of carious debris using only hand instruments and placement of a glassionomer cement (GIC) restoration. While small ART-GIC restorations are effective short-term replacements for lost tooth form, many larger ART-GIC restorations are defective after two years. Presently, resin-modified GICs (R-M GIC) are available which require no special activation equipment and handle easily in field settings. This study measured the com- pressive, tensile, and shear bond strengths to enamel and dentin of a conventional ART-GIC (Fuji IX) and two R-M GICs (Fuji Plus and Advance) at a powder-to-liquid ratio of 3.6:1. The compressive strengths of the GICs tested were significantly different. Fuji IX had the highest compressive strength, and Advance had the lowest strength (p < 0.05). The tensile strength of the R-M GICs was greater than that of the ART-GIC. Fuji Plus showed the highest shear bond strength to enamel and dentin and was significantly different from both Fuji IX and Advance. A clinical protocol is presented followed by case reports where the ART technique was used for management of acute caries in a modern dental setting.     

A comparison of microtensile bond strengths of several dentin bonding systems to primary and permanent dentin.

OBJECTIVES: Limited information exists with regard to the adhesive ability of glass ionomer cements (GIC) and recently developed resin-based dentin bond systems to primary dentin. The aim of this study was to compare the microtensile bond strength of a conventional GIC (Fuji IX), a resin-modified GIC (Fuji II LC), and two resin-based dentin adhesives (Prime and Bond NT with NRC and Single Bond). The bonded interfaces were also observed using field emission electron microscopy(FE-SEM). METHODS: Microtensile bond test specimens were prepared on superficial dentin of primary and permanent molars. The specimens were bonded according to each manufacturer's instructions except for Prime and Bond NT/NRC which used Silux Plus resin composite instead of Dyract. Hour-glass shaped specimens were created (diameter of 1.2+/-0.02 mm) and stressed in tension at a crosshead speed of 1mm/min. Results were analyzed using two-way ANOVA and LSD test, fracture modes were analyzed using the Mann-Whitney U-test and Kruskall-Wallis test. Twelve specimens were prepared for each material on primary and permanent dentin. Samples were prepared in the same manner, then critical point dried, fractured and sputter-coated for the FE-SEM observations. RESULTS: Two-way ANOVA showed the overall bond strengths were greater for the permanent dentin compared with primary dentin. However, for individual material comparisons no differences among the bond strengths to primary and permanent dentin for Fuji IX (9.7, 12.2 MPa), Fuji II LC (16, 20.1 MPa), Prime & Bond NT/NRC (18.1, 21.6 MPa) and Single Bond (18.2, 21.6 MPa), were detected. However, Fuji IX bond strengths were significantly lower than the other systems tested when bonded to either primary or permanent dentin (p<0.05). Failure mode showed cohesive failure of GIC and mostly adhesive failure for the resin-based adhesives. The FE-SEM observations showed hybrid-like layer formation for the GIC materials and hybrid layer formation for the resin-based adhesives. SIGNIFICANCE: The materials tested would be suitable for bonding to either primary or permanent dentin, but the resin-modified GIC or resin-based systems are likely to provide a stronger bond than the conventional GIC, Fuji IX.     

Hydroxyapatite particle characteristics influence the enhancement of the mechanical and chemical properties of conventional restorative glass ionomer cement

The aims of this study were to improve the mechanical and chemical properties of conventional restorative glass ionomer cement (GIC) by adding hydroxyapatite (HAp) preparations with different characteristics, and to investigate the underlying reaction mechanisms. Fuji IX GP? was used as the control GIC. The experimental GICs consisted of four HAp-particles with different characteristics added at 8 mass% to Fuji IX-powder. All cements were prepared by mixing with Fuji IX-liquid (P/L=3.6). Four HAp-particles were analyzed, and then the mechanical strengths and the fluoride-ion- release-recharge-behaviors of five GIC groups were evaluated. The results of this study demonstrate that the addition of HAp particles with highly reactive properties such as high specific surface area can enhance the flexural strength and fluoride ion release properties of conventional restorative GIC. Our results further indicate that HAp functions as an adsorbent and an ion exchangeable agent, resulting in improved mechanical and chemical properties of GIC.     

Effect of one-year water storage on the surface microhardness of resin-modified versus conventional glass-ionomer cements.

OBJECTIVES: Conventional and resin-modified glass-ionomer cements (GIC, RM-GIC) are available for clinical use as restorative materials or as liners and bases. This study was conducted to compare the effect of a 12-month storage period in water on the surface microhardness, measured in Vickers units (VH), between a GIC and a RM-GIC group and to determine if the addition of resins improved the GIC microhardness. METHOD: VH microhardness was assessed in three GIC: Ketac-Fil, Ketac-Molar and Ketac-Silver (KF, KM, KS) and three RM-GIC: Photac-Fil, Fuji II LC and Vitremer (PF, FU, VI) stored in distilled water at 37 degrees C for 12 months. Measurements were taken at 1, 7, 15, 30, 90, 180 and 365 days. The statistical evaluation was done by means of one-way analysis of variance (ANOVA) and Tukey's multiple comparison tests. RESULTS: There are significant VH differences among the materials studied and within each material over storage time. GICs, except for KS, showed a higher VH throughout the study period. Among the RM-GIC, VI showed a significantly higher VH at 12 months than at 1 day. The VH of PF diminished in the final stage of the study, whereas that of FU stabilized. SIGNIFICANCE: The results suggest that the addition of resins to the GIC did not appear to improve the surface microhardness of these materials. Furthermore, the surface microhardness of both the conventional and resin-modified glass-ionomers suffered variations over time. However, these materials should not be deemed inadequate for use in clinical applications. Probably, conventional and resin-modified GICs placed in the oral environment would not be affected to the same extent as in in vitro tests.     

Influence of food-simulating solutions and surface finish on susceptibility to staining of aesthetic restorative materials

OBJECTIVES: To determine the degree of surface staining of resin-based composites (RBCs) and glass-ionomer cements (GICs) after immersion in various stains and food-simulating solutions (FSS). METHODS: Six tooth-coloured restorative materials were used: a light-cured microfilled RBC (Durafil, Kulzer), a light-cured microglass RBC (Charisma, Kulzer), a polyacid-modified RBC (F2000, 3M/ESPE), a conventional GIC (Fuji IX, GC) and two resin-modified GICs (Fuji II LC, GC; Photac Fil, 3M/ESPE). Disk-shaped specimens were prepared and tested with either a matrix finish or polished using wet silicon carbide papers up to 2000 grit. All specimens were immersed in 37 degrees C distilled water for 1 week, followed by three different FSS (water, 10% ethanol, Crodamol GTCC) and five stains (red wine, coffee, tea, soy sauce and cola) for a further 2 weeks. Three specimens of each material for each stain were tested. Colour coefficients (CIE L* a* b*) were measured by a spectrophotometer after each treatment. The change in colour (DeltaEn) was calculated using the formula: DeltaEn=[(DeltaLn+(Deltaa(n))2+(Deltab(n))2]1/2. RESULTS: Distilled water caused no perceptible colour change as tested by ANOVA and Tukey's tests. The effect of surface finish on staining was not statistically significant (P>0.05). There was no strong interaction between FSS and stains or between FSS and materials. There was a strong interaction between surface and material, and stain and material (P<0.001). CONCLUSIONS: All materials were susceptible to staining by all stains especially coffee, red wine and tea; Fuji IX showed the least susceptibility and F2000 the greatest.     

Effects of N-vinylpyrrolidone (NVP) containing polyelectrolytes on surface properties of conventional glass-ionomer cements (GIC)

It has been found that polyacids containing an N-vinylpyrrolidinone (NVP) comonomer produces a glass inomer cement with improved mechanical and handling properties. The objective of this study was to investigate the effect of NVP modified polyelectrolytes on the surface properties and shear bond strength to dentin of glass ionomer cements.Poly(acrylic acid (AA)-co-itaconic acid (IA)-co-N-vinylpyrrolidone) was synthesized by free radical polymerization. The terpolymer was characterized using ¹H NMR, FTIR spectroscopy and viscometry for solution properties. The synthesized polymers were used in glass ionomer cement formulations (Fuji II commercial GIC). Surface properties (wettability) of modified cements were studied by water contact angle measurements as a function of time. Work of adhesion values of different surfaces was also determined. The effect of NVP modified polyacid, on bond strength of glass-ionomer cement to dentin was also investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to one- and two-way analysis of variance (ANOVA) at α = 0.05.Results showed that NVP modified glass ionomer cements showed significantly lower contact angles (θ = 47°) and higher work of adhesion (WA = 59.4 erg/cm²) in comparison to commercially available Fuji II GIC (θ = 60° and WA = 50.3 erg/cm², respectively). The wettability of dentin surfaces conditioned with NVP containing terpolymer was higher (θ = 21°, WA = 74.2 erg/cm²) than dentin conditioned with Fuji conditioner (θ = 30°, WA = 69 erg/cm²). The experimental cement also showed higher but not statistically significant values for shear bond strength to dentin (7.8 MPa), when compared to control group (7.3 MPa). It was concluded that NVP containing polyelectrolytes are better dentin conditioners than the commercially available dentin conditioner (Fuji Cavity Conditioner, GC). NVP containing terpolymers can enhance the surface properties of GICs and also increase their bond strength to the dentin.     

Shear bond strength of resin-modified restorative glass-ionomer cements to dentin--an in vitro study

An in vitro study was carried out on 40 periodontally involved, caries free human maxillary and mandibular molars to evaluate shear bond strength of resin- modified restorative glass-ionomer cements to dentin. Teeth were divided into four groups, Group I--Fuji II (Conventional glass ionomer) Group II (Fuji II LC), Group III (Vitremer), Group IV (Geristore). Shear bond strength was tested using a transaxial testing machine. Results showed that shear bond strength of all resin-modified restorative glass-ionomer cements was higher than conventional glass ionomer (Fuji II) tested. No statistical difference was found between Fuji II LC and Geristore. However, bond strength of Vitremer was lower than Fuji II LC and Geristore but higher than Fuji II.     

Mineral loss on adjacent enamel glass ionomer cements restorations after cariogenic and erosive challenges

Objectives

the purpose of this study was to determine the mineral loss on surrounding enamel restored with glass ionomer cements (GIC) after erosive and cariogenic challenges.

Methods

Bovine enamel specimens were randomly assigned into six groups according to the restorative material: G1 – composite resin; G2 – high viscous GIC; G3 – resin-modified glass ionomer with nanoparticles; G4 – encapsulated resin-modified GIC; G5 – encapsulated high viscous GIC; G6 – resin-modified GIC. After restorative procedures, half of specimens in each group were submitted to caries challenge using a pH cycling model for 5 days, and the other half were submitted to erosive challenge in citric acid for 10 min. Before and after the challenges, surface Knoop microhardness assessments were performed and mineral changes were calculated for adjacent enamel at different distances from restorative margin.

Results

Data were compared for significant differences using two-way ANOVA and Student–Newman–Keuls tests (p < 0.05). Erosive challenge significantly reduced enamel surface hardness, but no significant difference was observed irrespectively restorative materials (p > 0.05). The cariogenic challenge promoted a higher surface hardness loss for the resin-modified GIC (G4) and only for the High viscous GIC (G2) an increase in surface hardness was observed. For enamel analyses, significant differences were observed with respect to the different materials (p < 0.001) and distances (p = 0.023). Specimens restored with the composite resin presented higher mineral loss and specimens restored with the conventional high viscous GIC and the encapsulated resin-modified GIC presented the lowest values for mineral loss.

Conclusion

The GICs exerts protective effect only for cariogenic challenge.     

Effect acidic and alkaline/heat treatments on the bond strength of different luting cements to commercially pure titanium

Objective

The purpose of this study was to characterize the effects of either acidic or combined alkaline/heat treatments on the surface of grit-blasted commercially pure (cp) titanium. The effects of the previous treatments on the shear bond strength (SBS) of cp titanium to conventional glass ionomer, resin-reinforced glass ionomer and self-adhesive resin luting cements were evaluated.

Methods

Titanium discs were machined and received one of the following treatments; grit-blasting (GB), grit-blasting followed either by etching in HNO₃/HF solution (GB/Ac) or by combined 5 M NaOH treatment/heat treatment at 600 °C for 1 h, then immersed for 24 h in SBF solution before cementation (GB/Ak). The treated surfaces were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and laser-induced brake-down spectroscopy (LIBS). Discs were cemented either by Fuji I, Fuji Plus or Rely X™ Unicem luting cements. The SBS was evaluated and the debonded discs were investigated by SEM.

Results

Two prominent results were revealed; first, GB/Ak treatment showed the highest SBS than the other treatments (P < 0.0001). Second, Rely X™ Unicem showed the highest SBS than the other cements (P < 0.0001). Fuji I and Fuji Plus showed predominant cohesive type of failure, whereas Rely X™ showed predominant adhesive type of failure.

Significance

Combined alkaline/heat treatments of commercially pure titanium surface shows to be of beneficial effect in enhancing SBS to glass ionomer, resin-modified glass ionomer and adhesive resin luting cements.     

Glass ionomer cements used as fissure sealants with the atraumatic restorative treatment (ART) approach: review of literature

AIM: To review the success of newer, more-viscous aesthetic conventional glass ionomer cements (GICs), that have been marketed specifically for the atraumatic restorative (ART) technique or approach, when used as pit and fissure sealants. As part of this approach, enamel fissures adjacent to the ART restorations are conditioned with poly (acrylic) acid (PAA) and then usually sealed with a GIC, using the finger-press method. RESULTS: The newer GICs appear in vitro to penetrate adequately and seal occlusal fissures in permanent molar teeth, and clinical studies of the ART approach over three years have found sealant retention (full and partial) to be approximately 70%, with fissure caries approximately 0-4%. In two studies, fissure caries was significantly reduced in sealed as compared with unsealed teeth over three years. CONCLUSIONS: Although the results appear to be better with the newer than with earlier conventional GIC products, the ART studies have generally involved populations at low-risk to caries, and further improvements in the mechanical properties of the cements are required for optimal long-term clinical success. Etching the enamel fissures with phosphoric acid, instead of conditioning with PAA, before GIC sealant placement warrants clinical investigation.     

Fluoride release of glass ionomer-based luting cements in vitro.

STATEMENT OF PROBLEM: There is considerable variation in generic formulation and in reported fluoride release from resin-modified glass ionomer luting cements. PURPOSE: This study compared fluoride release from 2 generically similar resin-modified glass ionomer luting cements (Vitremer and Advance) with release from 2 conventional glass ionomer luting cements (Ketac-Cem and Fuji I). MATERIAL AND METHODS: Ten specimen disks of each of the 4 luting cements were fabricated and immersed in deionized water in individual polystyrene jars. The jars were stored in a humidor at 37 degrees C between test periods. At the same time each day, for 28 days, fluoride release from each specimen disk was measured in parts per million by testing the storage water. RESULTS: The 4 luting cements tested showed an initial high concentration of fluoride release during the first week, followed by a gradual decrease over the study period. Vitremer luting cement demonstrated the greatest mean cumulative fluoride release in parts per million over the study period (198), followed by Fuji I (140), Ketac-Cem (110), and Advance (99) luting cements. CONCLUSIONS: Resin-modified glass ionomer luting cements showed fluoride release comparable to the conventional glass ionomer luting cements. Vitremer luting cement released more fluoride over the 28-day period than the other cements.     

Evaluation of Fluoride Release in Chitosan-Modified Glass Ionomer Cements

ObjectiveThis study assessed the influence of chitosan nanoparticles on the fluoride-releasing ability of 4 glass ionomer cement (GIC) through an in vitro analysis.MethodsFour types of GIC (type II light cure universal restorative, type II universal restorative, GC Fuji VII, and type IX) were modified with nanochitosan particles; 10% chitosan was added to the glass ionomer liquid. Six specimens for each of the 4 groups were created, using expendable Teflon moulds. Discs of each type of GIC (n = 6) were immersed in deionised water at various time intervals. Electrodes selective for fluoride ions were employed to analyse the amount of released fluoride at 1, 7, 14, 21, and 28 days.ResultsChitosan-modified GICs showed greater fluoride release than conventional GICs at all time points. All samples showed an initial high release of fluoride that tapered off with time. The total amount of fluoride released increased from the 1st day to the 28th day on adding chitosan to all the 4 types of GIC. Amongst those, type IX high-strength posterior extra with chitosan released a considerably higher quantity of fluoride at all time intervals.ConclusionsIn all the experimental groups, adding chitosan to the glass ionomer liquid had an accelerating effect on its fluoride-releasing property.     

Mechanical properties of glass ionomer cements affected by curing methods.

OBJECTIVE: The primary objective of the study was to assess the influence of externally applied 'command' set applications on the mechanical properties of several commercially available conventional glass ionomer cement (GIC). METHODS: Four different restorative GICs cements (Fuji IX FAST, Fuji IX, Ketac Molar Quick, Ketac Molar) were cured using three different methods, e.g. standard curing conditions (SC), ultrasonic excitation (UC) and by an external heat source (HC). The compressive strength of these samples was measured and the groups were compared using one-way ANOVA. A standard thermocouple (K-type) measured the temperature in GIC during curing. RESULTS: In general all experiments showed an increase in strength going from SC, UC to HC. Especially, the compressive strength of Fuji IX FAST and Ketac Molar increased by UC and HC compared to the SC values. The compressive strength of Fuji IX FAST as a function of time showed an increase in strength during 28d. There was a clear relationship between the temperature in the sample (SC相似文献