Short- and long-term fluoride release from glass ionomers and other fluoride-containing filling materials in vitro

Abstract – Test specimens of seven different glass ionomer filling materials and one fissure sealant were exposed to running water for 2 yr. One amalgam and one composite, both containing fluoride, were included for comparison. The fluoride release from the specimens was measured periodically after storing the specimens for 24 h or 1 wk in a small amount of water. The fluoride release From the glass ionomers decreased with time and a constant level was reached for most products during the 2-yr period. The release was increased by lowering the _pH of the storage solution. The release from the glass ionomers was clearly greater than from the amalgam and the composite.     

Fluoride release and uptake by glass ionomers

Abstract – The aim was to study the fluoride release 1) from 7 and 15-month-old glass ionomer specimens after treating them with fluoride; 2) from fresh compared with matured material; and 3) from specimens stored for 29 months in running water. Glass ionomer test specimens which had been in running water for first 7 then 15 months were treated with a 50 ppm fluoride solution after which the specimens were again exposed to running water for first 24 h and then 1 wk. The fluoride release was measured after each of the two periods of time. The fluoride treated specimens released more fluoride than the nontreated ones. This effect was not observed with composite resin specimens which were studied for comparison. Fluoride release from fresh glass ionomer specimens was observed to be 3–10 fold compared to specimens that had matured for 3 days. The release of fluoride from specimens that had been in running water for 29 months was measured and the results were compared with those of earlier measurements. It was found that the release reached a constant level for all tested glass ionomers during the second year.     

Fluoride release and uptake by glass ionomers

The aim was to study the fluoride release 1) from 7 and 15-month-old glass ionomer specimens after treating them with fluoride; 2) from fresh compared with matured material; and 3) from specimens stored for 29 months in running water. Glass ionomer test specimens which had been in running water for first 7 then 15 months were treated with a 50 ppm fluoride solution after which the specimens were again exposed to running water for first 24 h and then 1 wk. The fluoride release was measured after each of the two periods of time. The fluoride treated specimens released more fluoride than the nontreated ones. This effect was not observed with composite resin specimens which were studied for comparison. Fluoride release from fresh glass ionomer specimens was observed to be 3-10 fold compared to specimens that had matured for 3 days. The release of fluoride from specimens that had been in running water for 29 months was measured and the results were compared with those of earlier measurements. It was found that the release reached a constant level for all tested glass ionomers during the second year.     

Fluoride release from three glass ionomers, a compomer, and a composite resin in water, artificial saliva, and lactic acid

The amounts and the pattern of fluoride release from one metal-reinforced glass ionomer cement, two resin-modified glass ionomer cements, one compomer, and one composite resin placed in double-distilled water, artificial saliva, and lactic acid were evaluated in this study. Measurements of fluoride ion release were made for a total of 105 cylindrical specimens (10 mm in diameter and 1.5 mm in height). They were taken over a period of 16 weeks at the intervals of 4, 8, 12, and 24 hours, as well as 2, 3, 7, 14, 28, 56, and 112 days. The pattern of fluoride release was similar for all of the examined materials. The greatest amount of fluoride was released from the metal-reinforced glass ionomer Argion. The resin-modified glass ionomers Vitremer, Fuji II LC; the compomer Dyract; and the composite resin Tetric followed in ranking order. The pH of the environment strongly affected the fluoride release from the materials. There was a significant difference (P < 0.001) in the amounts of fluoride released in lactic acid vs water and artificial saliva, whereas, there was no significant difference (P > 0.05) in the amounts of fluoride released in water vs artificial saliva.     

Effects of temperature on the fluoride release and recharging ability of glass ionomers

This study investigated the effects of environmental temperature on the fluoride release and recharging ability of glass ionomers. Five disk specimens (15 mm in diameter and 1 mm thick) were made of each of the following materials: a conventional luting glass ionomer, two high viscosity restorative glass ionomers and a restorative resin-modified glass ionomer. The fluoride release of each material was measured at 4 degrees C, 37 degrees C and 55 degrees C. An additional three groups, which were made of the same materials, were stored in distilled and deionized water for 30 days and recharged in 250 ppm fluoride solution at 4 degrees C, 37 degrees C and 55 degrees C for five minutes. The fluoride re-release was measured daily from two days prior to two days after the recharging process. At all temperatures, the luting glass ionomers showed the greatest fluoride release and recharging ability, followed by the resin-modified glass ionomer, then the high viscosity glass ionomers. For each material, the fluoride release increased with increasing temperature and all glass ionomers showed greater recharging ability at higher temperatures. An increase in environmental temperature increased both the fluoride release and recharging of the glass ionomers. This may be important in developing regimes for improving the delivery of topical fluoride products.     

Fluoride release in vitro from various glass ionomer cements and resin composites after exposure to NaF solutions

The release of fluoride from 1) discs made from five glass ionomer cements and two composites, and 2) the same discs after exposure to different NaF solutions, were studied. The specimens were placed in distilled water for 10 wk. After 24 h and then once a week, the specimens were transferred to fresh distilled water. After 5 wk, the specimens were divided into four groups and exposed to 0, 0.02, 0.2 and 2% NaF solutions for 5 min. The fluoride release was highest during the first week after preparation, after which it decreased sharply and then more slowly. The amount of fluoride released was ordered: liner/base>restorative glass ionomer>composites. The composites released significantly less fluoride than the glass ionomer cements. After exposure to NaF, the fluoride release was significantly higher for the silver cermet material than for the other glass ionomers tested. From a clinical point of view, the results from this study imply that glass ionomer restorations may act as intraoral devices for the controlled slow release of fluoride at sites at risk for recurrent caries.     

Effect of acetic acid on the fluoride release profiles of restorative glass ionomer cements.

OBJECTIVES: This study investigates the fluoride release of glass ionomers in an acetic acid solution in order to substantiate a model according to which the short-term release results from an elution of loosely bound fluoride and the long-term release from an erosive leaching of the glass particles in the bulk of the cement. METHODS: Individual fluoride release profiles of five specimens of 10 acid-base setting restorative glass ionomers were obtained by determining the amounts of fluoride released by each sample at 37 degrees C in consecutive elutions for up to 140 days with 25 ml of a 0.01 mol/l acetic acid solution with pH = 4. Differences in the fluoride release profiles were determined with a Multivariate Data Analysis on the basis of a Principal Component Analysis. RESULTS: The fluoride release profiles of the 10 glass ionomers can be classified into five distinct groups which are characterized by a cumulative fluoride release described by the equation [F]c = [F]l t/(t + t1/2) + beta square root of t. The parameters ([F]l, t1/2) and beta are characteristic for the materials in the groups, and refer to the short-term and long-term fluoride release, respectively. The acidic solution enhances both processes compared to an elution in water, the effect being more pronounced for the long-term release. SIGNIFICANCE: The fluoride release mechanism is intrinsically the same as determined for elutions in water. The increased amount of fluoride released under acidic conditions, especially in the long term, corroborates that an erosive leaching of the glass particles in the bulk of the cement accounts for the long-term fluoride release.     

Fluoride release from a fluoride-containing amalgam, a glass ionomer cement and a silicate cement in artificial saliva

This study aimed to compare the fluoride release from a flouride-containing amalgam, a silicate cement and a glass ionomer cement in artificial saliva. After storing specimens in an artificial saliva for 7 weeks, the fluoride content in the solvent was measured by a spectrophotometric method. The fluoride release from silicate cement was about 5 times greater than from glass ionomer cement, which again showed a release 4 times greater than the fluoride-containing amalgam. The fluoride release relative to fluoride content in test specimens was greater from fluoride-containing amalgam and silicate cement than from glass ionomer cement.     

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.     

In vitro caries-inhibitory properties of a silver cermet

Recurrent caries is one of the primary causes of failure of dental restorations. One method for reducing the frequency and severity of this problem is the use of fluoride-releasing restorative materials. The glass-ionomer cements are a type of fluoride-releasing material. They have been used extensively in recent years for a variety of clinical applications. However, in comparison with other restorative materials such as amalgam and composite resins, glass ionomers have relatively poor physical properties. Sintering of silver particles to glass-ionomer powder is a means of improving these physical properties. The sintered material is called a silver-glass ionomer or silver cermet. This study examined the in vitro caries-inhibitory potential of a silver cement by means of two methods. First, long-term fluoride release was measured. Second, an artificial caries system was used for evaluation of caries inhibition by cerment restorations in extracted teeth. In comparison with a standard glass-ionomer restorative material, fluoride release from the cermet material was significantly less throughout a 12-month period. The results from the artificial caries system indicated that this decreased fluoride release corresponded with a lesser degree of caries inhibition. Lesions around cermet restorations in both enamel and root surfaces were significantly more severe than those around conventional glass-ionomer restorations. However, in comparison with amalgam and composite resin restorations, the cermet did have some cariostatic activity.     

Effect of air polishing on the fluoride release of (resin-modified) glass ionomer cements and of a polyacid-modified composite resin

Eight different conventional and resin-modified glass ionomers as well as a polyacid-modified composite were air polished and their fluoride release was determined in comparison to untreated controls. The air polishing was done with two different devices at medium and maximum setting for powder and water. Ninety discs of 1.5 mm thickness and 7.0 mm diameter were produced from each cement. These discs were stored in 5 ml deionized water at 37°C. After 1 day and 1, 4, 8, 12, and 16 weeks, the specimens were transferred into new vials with fresh deionized water. From the 4th week onward, the specimens (except for the untreated controls) were air polished on half of their upper and lower surfaces for 2 s each before being put into a new vial. After 20 weeks the fluoride released during the previous 4 weeks was determined with a fluoride ion-sensitive electrode. With the exception of Ketac-Cem, all cements released significantly more fluoride ions after air polishing, irrespective of the devices' settings. The differences in the amount of fluoride released among the investigated materials were greater than the changes in fluoride release patterns caused by air polishing. Air polishing increased the fluoride release by 20–60% in most of the materials investigated. Received: 10 February 1998 / Accepted: 25 May 1998     

Fluoride-containing restorative materials

Dental practitioners are exposed to an increasing number of dental materials, which claim the benefits of fluoride release. The purpose of this paper is to critically review the literature of these materials. Glass ionomers, resin modified glass ionomers, compomers, resin composites, fissure sealants and amalgam are discussed. It is clear that a long-term measurable release of fluoride can be observed from certain restorative materials, in vitro, particularly glass ionomer cement, resin modified glass ionomer cement, fluoridated cements, fluoridated dental amalgam and certain fissure sealants. In general, the rate of fluoride release is not constant but exhibits a relatively rapid initial rate, which decreases with time. However, the fluoride release profiles may be dependent on specific formulation and on experimental design and sampling methods. These materials may feature greater longevity, a reduced incidence of marginal failure, an elevated concentration of fluoride in contingent plaque, together with an antibacterial action when compared with non-fluoride releasing materials. In addition, fluoride-releasing materials may perform better in caries inhibition in artificial caries model studies than non-fluoridated materials. While any, or all, of these anti-cariogenic effects may be associated with fluoride release, a direct relationship between fluoride release profiles and such effects has not been determined in vivo.     

Release and recharge of fluoride by restorative materials

This study investigated the release and recharge of fluoride by restorative materials. Resin-modified glass ionomers (RGIs), polyacid-modified composite resins (PMCRs) and resin composite containing fluoride were used for comparison of fluoride release. Non-fluoride-releasing resin composite was used as a control. The amounts of fluoride release from RGIs and PMCRs remarkably increased in the citrate-phosphate acid buffer compared with distilled water. The amounts of fluoride recharged in RGIs increased with the concentration of NaF solution, but those of PMCRs exposed to all concentrations of NaF solutions were less than 1.5 ppm. Neither resin composite containing fluoride and non-fluoride-releasing resin composite gave any evidence of recharge. RGIs and PMCRs affected by acid buffer solution could not recharge much fluoride even if they were immersed in the 1000 ppmF NaF solution. The results suggested that the matrix of RGIs and PMCRs functioned as a reservoir of fluoride, but the functions were lost by acid attack.     

Fluoride release from glass ionomer-lined amalgam restorations

This study evaluated the amount of fluoride released from glass ionomer-lined amalgam restorations. 50 human extracted molars were divided into five groups of 10 teeth each. Group 1: No restorations. Group 2: Class V cavities (2 x 2 x 7 mm) were made on the facial and lingual surfaces and restored with Dispersalloy amalgam. Group 3: Same as Group 2 except 1 mm of Ketac-Bond glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 4: Same as Group 2 except 1 mm of Chelon-Silver glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 5: Same as Group 2 except 1 mm of Ketac-Silver GIC was used before amalgam insertion. Before any treatment, all samples were placed in polyethylene vials with 4 ml of deionized water and thermocycled (100x) for baseline fluoride release levels. After restoration, each tooth was placed in a vial with 4 ml of fresh deionized water. At weekly intervals, each tooth was removed from its aqueous medium and transferred to another vial containing 4 ml of deionized water. Fluoride release was measured four times at weekly intervals with an Orion #9609 fluoride-ion electrode. At one week, Ketac-Bond released significantly more fluoride than Ketac-Silver (P less than 0.01) which released significantly more fluoride than Chelon-Silver (P less than 0.01). At four weeks, there was no significant difference in fluoride release between Chelon-Silver and Ketac-Silver, but Ketac-Bond released significantly more fluoride than either of the other materials (P less than 0.01).     

Short-term fluoride release from various aesthetic restorative materials

The short-term fluoride release of a giomer (Reactmer), a compomer (Dyract AP), a conventional glass ionomer cement (Fuji II Cap) and a resin-modified glass ionomer cement (Fuji II LC) was evaluated and compared. Specimen discs (6 +/-0.2 mm diameter and 1 +/- 0.2 mm thick) were prepared for each material using custom molds. Each disc was placed in 1 ml of deionized for 24 hours at 37 degrees C. After one day, the water was extracted and analyzed. The specimen discs were then re-immersed into another 1 ml of fresh deionized water. The procedure of removing and refilling the water was repeated for 28 days. Sample solutions taken during the first seven days and at days 14, 21 and 28 were introduced into a capillary electrophoresis system using field amplified sample injection (FASI) to determine fluoride release. Data was analyzed using factorial ANOVA/Scheffe's post-hoc test at significance level 0.05. An initial fluoride "burst" effect was observed with glass ionomers. Both compomer and giomer did not show an initial fluoride "burst" effect. With the exception of the compomer, fluoride release at day one was generally significantly greater than at the other time intervals. The glass ionomers released significantly more fluoride than the compomer and giomer at day one. Although fluoride release of the giomer was significantly greater than the other materials at day seven, it became significantly lower at day 28.     

Fluoride release from restorative materials and a luting cement

STATEMENT OF PROBLEM: In addition to conventional glass ionomers, a considerable number of different types of materials have been formulated to release fluoride. Variation in composition results in quantitative differences in the amount of fluoride release by these materials. PURPOSE: This study evaluated and compared fluoride release in distilled water from different types of restorative materials and a luting cement. MATERIAL AND METHODS: Fluoride release from 4 glass ionomer formulation restorative materials (Miracle-Mix, Fuji ionomer type III, Fuji II LC improved, and Ketac-Silver), a luting cement (Ketac Cem), a compomer (Compoglass Flow), 2 sealants (Fissurit F, Helioseal F), and a composite resin (Tetric) was evaluated at time intervals of 4, 8, 12, and 24 hours and 2, 3, 7, 14, 28, 56, and 112 days. Seven disks of each material were made and stored for equilibration in double distilled water at 37 degrees C for the time of each measurement. The equilibrated solution was analyzed for fluoride with a TISAB and an ion-specific combination electrode (ORION 960900) connected to an expandable ion analyzer (Crison micropH 2002). Data were analyzed by means of univariate analysis of variance, the Dunnett C post hoc test, and repeated measures analysis. RESULTS: Fluoride was released from all the evaluated materials, with considerable variation in the rate of release but a similar pattern. Among the materials tested, fluoride release from glass ionomer formulations was greater than that from composite resin formulations; the rank of decreasing order was as follows: Miracle Mix > Fuji III, Ketac Cem > Fuji II LC > Ketac Silver, Compoglass F > Fissurit F, Helioseal F > Tetric (> indicates statistical significance; P< .05). CONCLUSION: Under the conditions of this study, glass ionomer formulations and the compomer released more fluoride than the sealants and the composite resin tested.     

Solubility and fluoride release in ionomers and compomers.

OBJECTIVE: The degree of solubility and the fluoride release of glass-ionomer cements and "compomers" were determined as a function of time. METHOD AND MATERIALS: Three conventional glass-ionomer cements, three hybrid ionomers, and two compomers were included in the study. Disk-shaped specimens were prepared and immersed in a lactic acid solution. Solubility was evaluated from determinations of loss of mass as a function of time. To evaluate fluoride release, similar specimens were immersed in 50 mL of deionized water to which 50 mL of buffer solution was added. A fluoride ion detector was used to read the concentration of fluoride ion in the overall solution at different times after immersion. RESULTS: Material and time factors had a significant influence on results. The compomers showed less corrosion and fluoride release than the ionomers. Some correlation was found between solubility and fluoride leakage values. CONCLUSION: Components of both the ionomers and compomers that were studied can dissolve in water. The materials leak fluoride ions in amounts that differ according to the characteristics of the individual products.     

Fluoride release and re-uptake in direct tooth colored restorative materials.

OBJECTIVES: Glass ionomers may be "recharged" through topical fluoride (F-) treatments; however, this reported "recharging," may be attributed to surface changes after F- treatment. This study examined differences in F- release and re-uptake among dual-cured and chemically-cured glass ionomers, and a photo-cured F- releasing composite. A secondary goal was to determine if tensile strength or surface roughness changed due to F- release, or F- re-uptake and re-release. METHODS: In Phase 1, initial surface roughness and diametral tensile strength were measured. F- release was measured for 30 days. Strength and roughness were then remeasured. In Phase 2, surface roughness was measured, then materials were treated with a 5000 ppm neutral F- gel, the same gel without F-, or phosphoric acid. F- release was measured for 30 days, then final surface roughness and strength were determined. RESULTS: Significant differences were found in amount and rate of F- release, and F- re-uptake and re-release among study materials and enamel controls (p < 0.001). The amount and rate of F- re-release after NaF treatment differed significantly from F- release after acid treatment in glass ionomers, although both groups showed increased F- release after surface treatment (p < 0.001). There were no significant changes in tensile strength or surface roughness after F- release or F- re-uptake and re-release as determined by ANOVA. SIGNIFICANCE: The results of this in vitro study indicate that applications of neutral 5000 ppm F- gel to aged glass ionomer restorations results in a significant fluoride uptake and subsequent release. The data suggest that the application of neutral fluoride gel to glass ionomer restorations in situ may result in increases in oral fluoride concentrations, without affecting the restoration's surface roughness or tensile strength.     

含氟充填材料释氟吸氟和再释氟的研究

目的 为了研究含氟充填材料能否长期稳定释放氟而发挥抗龋效能,本文观察了玻璃离子水门汀和含氟复合树脂在用含氟牙膏处理前后两个时期的释氟情况。方法 第一阶段,将玻璃离子水门汀和含氟复合树脂各６个标本,分别浸泡于去离子水中,测定其在不同时间氟的放量;第二阶段。用含氟牙膏处理各标本后,再测定其在不同时间氟的释放量。结果 当这两允填材料释氟水平降低后,用含氟牙膏处理,琪 释放量明显回升     

Comparison of the effect of topical fluorides on the commercially available conventional glass ionomers, resin modified glass ionomers and polyacid modified composite resins--an in vitro study

This study was undertaken to assess the effect of a single application of three professionally applied topical fluoride agents (Sodium fluoride 2%, Stannous fluoride 8% and APF 1.23%) on the surfaces of six modern esthetic restorative materials used in pediatric dentistry viz., two conventional glass ionomers (Fuji II and Shofu-restorative), two resin modified glass ionomers (Vitremer, with and without glaze, and Photac-fil Quick) and two Polyacid modified composite resins (Luxat and Hytac Aplitip). Mean surface roughness and surface micro hardness (SMH) measurements were the parameters employed for comparison. Results showed that APF gel applications significantly increased the surface roughness measurements and decreased SMH of all tested materials, which was pronounced in conventional glass ionomers when compared with resin modified glass ionomers and polyacid modified composite resins. NaF and SnF2 produced a statistically significant increase in the surface roughness of conventional glass ionomers without any significant change in surface roughness and SMH on rest of the materials tested, except for NaF on SMH values of Fuji II, which was statistically significant.