Fluoride release and uptake from glass ionomer cements and composite resins

The aim of this investigation was to evaluate fluoride release and uptake from 4 glass ionomer cements (GICs)--Vitremer (VIT), Fuji II LC (FII LC), Fuji IX (FIX), Chelon Fill (CHE)--and 2 composite resins (CRs)--Heliomolar (H) and Zeta-100 (Z-100). Eight discs (8 mm x 2 mm) were made of each material and were stored in plastic vials containing artificial saliva at 37 degrees C. In group 1 (N = 3), the specimens were immersed in artificial saliva which was changed daily for 25 days. In group 2 (N = 5), besides receiving the same treatment as group 1, the specimens were immersed, after 24 hours, in a fluoride solution (1% NaF) for 1 min before daily saliva change. An ion-specific electrode (9609 BN-Orion) connected to an ion analyzer (SA-720 Procyon) was used to determine the amount of fluoride released at days 1, 2, 5, 10, 15, 20 and 25. Data were analyzed using two way ANOVA and Friedman's test. GICs released more fluoride during the first day and after this period the mean fluoride released decreased. Composite resin H released fluoride during the first day only and Z-100 did not release fluoride. In terms of NaF treatment, CRs did not show fluoride uptake, whereas the GICs showed fluoride uptake (VIT = FII LC = CHE > FIX).     

Fluoride release by silicate cements and composite resins

abstract – The purpose of the study was to determine the fluoride content of acrylic and composite resins and to study the release of fluoride from these materials in comparison to the release from silicates. The analytical results showed that one composite contained approximately the same amount of fluoride as is generally reported for silicates. The other resins contained none or only minimal amounts of fluoride. The release of fluoride was studied by measuring the uptake of fluoride by synthetic hydroxylapatite. Rectangular test specimens, 2 × 2 × 12 mm, made of the fluoride-containing resin were shaken in a neutral (pH 6.8) and an acidic (pH 5.8) solution with the hydroxylapatite for 7 weeks. The apatite was analyzed for fluoride each week and the test specimens were then transferred to a fresh solution with new apatite. As a control, a composite without fluoride was studied in the same way. For comparison two silicate cements were also included in the study. The results show that, during the first week, the uptake of fluoride by the apatite was greater from the silicates than it was from the composite. After that period the uptake continued at a lower level and did not show any marked decrease during the observation period. This continued uptake was about the same from both the silicates and the composite.     

Fluoride release from a polyacid-modified resin composite and 3 resin-modified glass-ionomer materials.

OBJECTIVES: The purposes of this study were to compare the fluoride ion release from a freshly mixed polyacid-modified resin composite, or "compomer" (Dyract), and 3 resin-modified glass-ionomer cements (Fuji II LC, Photac-Fil, and Vitremer) and to compare the use of 3 units for measuring fluoride release. METHOD AND MATERIALS: Five specimens (3.0 x 2.7 mm) of each material were prepared. The specimens were placed in polypropylene vials with 2 mL of deionized water and stored at 37 degrees C. The solutions were replaced weekly and the levels of fluoride ions were analyzed at days 1, 7, and 30 and subsequently every 28 days for 253 days. Fluoride measurements were carried out using a fluoride ion-selective electrode connected to a pH ion-selective electrode meter. Fluoride ion release was measured in parts per million, micrograms per square centimeter, and micrograms per cubic millimeter. RESULTS: Fuji II LC, Photac-Fil, and Vitremer showed high initial release values, which decreased exponentially and then showed a slow decline during the ensuing time. Dyract released significantly less fluoride ions during the first 84 days than did the 3 resin-modified glass-ionomer cements and maintained this low level of release throughout the study period. The amounts of fluoride ion release measured at any time interval varied with the units of measurement chosen, but the pattern of release remained the same. CONCLUSION: There was a wide variation in the amounts of fluoride ions released from related products, but the patterns of release were similar and unaffected by the units of measurement used.     

Fluoride release of polyacid-modified composite resins with and without bonding agents.

OBJECTIVES: The aim of this study was to investigate the influence of the proprietary bonding agents Hytac OSB (OSB) (Espe), Prime&Bond 2.1 (PB) (Dentsply DeTrey) and Syntac Single Component (SSC) (Vivadent) on the fluoride release of the corresponding polyacid-modified composite resins Hytac (HTC), Dyract AP (DAP) and Compoglass F (CGF), respectively. METHODS: Ten cylindrical specimens (6mm diameter and 3mm thick) of each polyacid-modified composite were prepared according to the manufacturers' instructions: five with bonding agent applied and five without bonding agent as a control. The specimens were immersed individually in 10ml ultra-pure water at 37 degrees C immediately after light-curing of the polyacid-modified composite resins. Over 140 days, the water was regularly renewed and the fluoride concentration eluted during each period was determined with a combined fluoride ion selective electrode. RESULTS: The fluoride release decreases according to the sequence: CGF>DAP>HTC. The bonding agent significantly reduces the fluoride released by DAP and CGF, respectively, by a factor 2-3 and +/-1.4. For HTC, the bonding agent reduces the fluoride released initially by a factor of +/-2, but the difference between the fluoride release with and without bonding agent becomes insignificant after approximately 3 weeks. SIGNIFICANCE: It can be concluded that the use of bonding agent can significantly reduce fluoride release of polyacid-modified composite resins in the long-term, and especially in the short-term. The decrease in fluoride release might reduce the material's potential to prevent recurrent caries.     

Fluoride release and uptake by aged resin-modified glass ionomers and a polyacid-modified resin composite

Little has been reported of the relationship of fluoride release and weight loss, and the effects of use of different fluoride agents on restorations, for the new generation of glass ionomer cements. The objectives of this study were to compare fluoride release of fresh and aged specimens of a polyacid-modified resin composite (Dyract), and of three resin-modified glass ionomer cements (Fuji II LC, Photac-Fil, Vitremer); and to correlate fluoride release and weight loss of aged specimens after recharging with three different fluoride agents. All materials showed high initial fluoride release immediately after uptake when using the agents. However, the levels of fluoride release dropped rapidly soon afterwards. Although initial fluoride release was significantly different between Dyract and the three resin-modified glass ionomers, when different fluoride agents were used on aged specimens after recharging, no significant differences were found after the first few hours. Linear regression analyses also showed no correlation between cumulative fluoride release and weight loss. Possible beneficial oral health effects may only be expected by frequent exposure of these materials to fluoride agents.     

Fluoride release from glass-ionomer cements, compomers and resin composites

The short and long-term fluoride release of 16 products (seven conventional glass-ionomers, five light-activated glass-ionomers, two polyacid-modified resin composites and two resin composites) commercialized as fluoride-releasing materials were measured. A potential link between the material type and its level of fluoride release was researched. The fluoride release was evaluated after different time intervals. Initial fluoride release from all materials was highest during the first 24 h and decreased sharply over the first week. Some groups of materials appeared to be significantly different after, respectively, 7 and 91 days. However, it was impossible to correlate the fluoride release of the materials by their type (conventional or resin-modified glass-ionomers, polyacid-modified resin composite and resin composite) except if we compared the products from the same manufacturer. The link between fluoride release and an acid-base reaction seems to be confirmed. The glass-ionomer composition (glass particles and polyacid's type, powder/liquid ratio) should have more influence on fluoride release than material type.     

Surface hardness properties of resin-modified glass ionomer cements and polyacid-modified composite resins

In this study the top and bottom surface hardness of two polyacid-modified composite resins (PMCRs), one resin-modified glass ionomer cement (RMGIC), and one composite resin were evaluated. The affect of water storage on their hardness was also investigated. The study was conducted using four different groups, each having five specimens obtained from fiberglass die molds with a diameter of 5 mm and a height of 2 mm. Measurements were made on the top and bottom surface of each specimen and recorded after 24 hours and again at 60 days. All tested materials showed different hardness values, and the values of top surfaces of the specimens were found to be higher than the bottom surface in all test groups. There was no statistical difference in the Vickers hardness (HV) values when the test specimens were kept in water storage. In conclusion Hytac displayed microhardness values higher than Vitremer and Dyract. We found the order of HV values to be Surfil > Hytac > Dyract > Vitremer, respectively. Vitremer presented the lowest microhardness level and Surfil the highest.     

Fluoride release and absorption at different pH from glass-ionomer cements.

OBJECTIVE: The aim of this study was to evaluate the fluoride release (release-tests) from two glass-ionomer cements (GIC), before and after NaF solution treatment (fluoride treatment) in different pH environments. MATERIALS AND METHODS: After 21 days, every second sample was submitted to fluoride treatment to simulate a fluoride recharge. After fluoride treatment every second sample was submitted to a further three days of long release-tests. Sample surfaces were analyzed by SEM before and after the release-tests in all pH solutions studied. RESULTS: The present study showed that GICs released fluoride ions for the duration of the examination period. For both materials the amount of F(-) released at low pH was considerably greater than at higher pH. The massive superficial breaking up observed by SEM probably promoted the releasing processes. Recharge is possible at different pH levels using NaF solution. CONCLUSIONS: Fluoride release may depend on GICs surface degradation caused by pH in the solution. The use of this kind of material may be an important issue in patients with with low pH saliva and with a high risks caries.     

Fluoride release from glass-ionomer cements in de-ionized water and artificial saliva

Most of the data reported on the release of fluorides from glass-ionomer cements are based upon measurements made in de-ionized water. De-ionized water does not represent the complex chemistry of the oral environment. In this study, an artificial saliva solution was used, and the data on the fluoride ions released into it from four glass-ionomer cements were compared with those obtained in de-ionized water. The glass-ionomer cements used were: Ketac-Fil (ESPE), Ketac-Silver (ESPE), Fuji-II (GC), and Miracle Mix (GC). Ten disc samples (2 cm x 0.1 cm) of each cement were prepared. Each was individually suspended in either de-ionized water or artificial saliva (five samples in each medium) and stored for 24 h at 37 degrees C, then transferred to fresh media for a total of 60 days. Collected media were buffered with TISAB, and fluoride was measured by a specific electrode. Artificial saliva was prepared according to Fusayama et al. (1963). The data obtained showed that: (1) glass-ionomer cements released more fluoride in de-ionized water than in artificial saliva; (2) Ketac-Fil released 20% more fluoride in saliva than did Fuji-II, the latter releasing 49% more fluoride than Ketac-Fil in de-ionized water; and (3) conventional glass ionomers released more fluoride than did meta-reinforced ones in both media.     

Effect of toothbrushing on fluoride release of polyacid-modified composite resins

The aim of the study was to evaluate the fluoride release of polyacid-modified composite resins (Dyract, Compoglass) submitted to brushing abrasion. Twenty samples were taken from each material and stored in a buffer solution (pH 4.0) for 12 days. Each day, the samples were transferred to a fresh solution. Ten samples of each material were brushed in an automatic tooth-brushing machine (250 strokes, 260-g load) every fourth day. The remaining samples were not subjected to brushing. Fluoride content of the solutions was measured with a fluoride sensitive electrode after the addition of TISAB. Statistical analysis demonstrated significant differences between the two materials with regard to cumulative fluoride release within the 12 days of the experiment. However, no difference was observed between the fluoride release of the brushed samples compared to the unbrushed specimens. This was true for both, the cumulative fluoride release and its release on the day following brushing. It is assumed that regular brushing of the tested materials did not influence their release of fluoride and that brushing of polyacid-modified composite resins does not lead to maintaining their initially high level of fluoride release. Received: 6 May 1999 / Accepted: 21 July 1999     

An ex vivo evaluation of resin-modified glass polyalkenoates and polyacid-modified composite resins as orthodontic band cements

OBJECTIVES: The objective of this ex vivo study was to assess the use of resin-modified glass polyalkenoates and polyacid-modified composite resins, as orthodontic band cements. MATERIALS AND METHOD: Plain stainless steel bands were cemented to 350 human extracted third molar teeth using 1 of 7 different cements. Following complete cement cure, half of each sample group was exposed to mechanical stress in a ball mill. Stressed and unstressed samples were tested in tension and the stress at which initial cement failure recorded. The mode of failure was recorded using an adhesive remnant evaluation. RESULTS: The mean band retention stresses offered by the cements studied ranged from 0.96 to 1.56 MPa. Fuji Ortho provided the highest mean band retention stress in "stressed" (1.56 MPa) and "unstressed" (1.45 MPa) states. Exposure to mechanical stress did not appear to significantly influence band retention or mode of cement failure for most cements. Fuji Ortho cement recorded the highest Weibull modulus for all cements tested. Virtually all samples failed at either the cement/enamel or cement band interface. CONCLUSIONS: Significant differences in band displacement stress values and mode of failure were demonstrated between the cements studied. However, generic comparisons were difficult to make.     

Fluoride release/uptake of polyacid-modified resin composites (compomers) in neutral and acidic buffer solutions

The aim of the present study was to evaluate the fluoride uptake/release of polyacid-modified resin composites (compomers) in neutral and acidic buffer solutions. Two compomers (Dyract and Compoglass) were tested and the conventional glass-ionomer cement (GIC) Vivaglass Base served as a control. Forty specimens were fabricated from each of the respective materials. Twenty of these specimens were placed in artificial saliva and the other 20 specimens in a fluoridated dentifrice slurry for 5 min. Then, 10 fluoridated and 10 non-fluoridated specimens were immersed in a neutral buffer solution (pH 6.8), and the other specimens were immersed in an acidic solution (pH 4.0). After 1, 2, 3, 4, and 5 days the samples were again placed in either a fluoridated dentifrice slurry or saliva for 5 min, after which time they were transferred to fresh buffer solutions. The fluoride content of the solutions was assessed with a fluoride sensitive electrode. Fluoride release from all the materials decreased continuously during the experiment, with a significantly higher release in the acidic solution compared to the neutral buffer solution. Fluoridation did not result in an increased fluoride release for the compomers. However, the conventional GIC revealed a significantly higher fluoride release after fluoridation. It is concluded that Dyract and Compoglass can not be replenished with fluoride, irrespective of the pH value of the environment.     

Antibacterial properties of dentin bonding systems, polyacid-modified composite resins and composite resins

This study examined the antibacterial activities of the bonding systems Syntac, EBS and Scotchbond 1, the polyacid-modified composite resins Hytac and Compoglass, and the composite resins Tetric, Z100 and Scalp-it. They were evaluated using the cariogenic bacteria Streptococcus mutans, Lactobacillus salivarius, Streptococcus sorbinus and Actinomyces viscosus in vitro with a modified cylinder drop plate agar diffusion assay. All adhesives of the dentin bonding systems and the polyacid-modified composite resins exhibited various degrees of antibacterial activity against all of the test bacteria. On the contrary, composite resins did not affect bacterial growth. The data suggest that the use of these adhesives and polyacid-modified composite resins may reduce the consequences of microleakage owing to their antibacterial properties.     

Effect of fluoride gels on micromorphology of resin-modified glass-ionomer cements and polyacid-modified resin composites.

OBJECTIVE: The purpose of this study was to evaluate the surface micromorphology of resin-modified glass-ionomer cements and polyacid-modified resin composites subjected to a neutral sodium fluoride (NNaF) and an acidulated phosphate fluoride (APF) gel application. METHOD AND MATERIALS: Thirty standardized cylindric specimens were randomly obtained from each of two resin-modified glass-ionomer cements-Fuji II LC Improved and Photac-Fil Aplicap-and two polyacid-modified resin composites--Dyract and F2000-amounting to 120 samples. After 1 week, the specimens were finished and polished with aluminum oxide disks. Surface treatments with fluoride gels, or distilled water as a control, were performed four times, interspersed with eight pH cycles, simulating high cariogenic challenges. Five calibrated evaluators assessed the surface micromorphology through photomicrographs. RESULTS: The Kruskal-Wallis test showed no significant difference between the control and experimental groups for Fuji II LC Improved and Dyract. Photac-Fil Aplicap showed less micromorphologic change as a result of distilled water application, unlike the NNaF and APF treatments, which revealed no significant difference from each other. For F2000, there was no significant difference between the surfaces treated by NNaF and distilled water; the highest degradation occurred with the APF. CONCLUSION: Both the resin-modified glass-ionomer cements and the polyacid-modified resin composites showed erratic behaviors concerning their micromorphology when subjected to fluoride gel application.     

Fluoride release from a new glass-ionomer cement

This study compared the amount and pattern of fluoride release from a new glass-ionomer-based material (nano-ionomer) with other restorative materials and correlated the surface area to volume of nano-sized filler with its capacity to release fluoride in the powder, more quickly increasing the fluoride. The materials evaluated were a nano-ionomer (Ketac N 100), a conventional glass-ionomer cement (GC Fuji II), a resin-modified glass ionomer cement (GC Fuji II LC), a compomer (Dyract F) and a fluoride-releasing resin composite (Tetric N Flow). A resin composite (Synergy Flow) served as the control. Ten specimens were fabricated from each of these materials using a customized metal mold. The fluoride release was measured every 24 hours for the first seven days, and on days 14, 21 and 28, a combination fluoride ion—selective electrode connected to an ion analyzer. The data was analyzed by one-way ANOVA and Tukey HSD test (p=0.05). An initial fluoride “burst effect” was seen with all of the materials, except for the control and compomer. The conventional glass-ionomer cement showed the highest fluoride release on the first three days. The nano-ionomer showed the maximum release of fluoride for the remaining days. A low constant level of fluoride release was seen from the compomer and fluoride-releasing resin composite throughout the study period.     

Microleakage between glass-ionomer cement and composite resins.

This study investigated the microleakage between glass-ionomer cement and Silux or Herculite with and without Scotchbond 2. Cavities were prepared in polymerized composite resin samples and "restored" with a glass ionomer cement with and without Scotchbond 2. The samples were thermocycled and immersed in 0.05% crystal violet solution for 2 hours, then embedded in clear casting resin, sectioned, and examined with an optical microscope. The results indicated that a high degree of dye penetration was found in samples of GC and Silux, and GC and Herculite without Scotchbond 2. The use of Scotchbond 2 significantly reduced the degree of dye penetration, but did not completely eliminate dye penetration.