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Ronald Verbeeck - One of the best experts on this subject based on the ideXlab platform.
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Effect of a neutral citrate solution on the Fluoride Release of conventional restorative glass ionomer cements.
Dental materials : official publication of the Academy of Dental Materials, 2005Co-Authors: Roeland De Moor, Luc Martens, Ronald VerbeeckAbstract:Summary Objectives This study investigates the effect of a neutral citrate solution on the Fluoride Release of 10 acid–base setting glass ionomer cements during 140 days at 37 °C. Methods Five disks of 10 acid–base setting restorative glass ionomers were prepared according to the manufacturer's instructions. These specimens were immersed individually in 25 ml of a 0.01 mol/l citrate solution with pH=7. Over 140 days, the solutions were regularly renewed and the Fluoride concentration eluted during each period was determined with a combined Fluoride ion selective electrode. Results The cumulative Fluoride Release was the result of an initial high Release that ceased after some time and a long-term of low Fluoride Release. The long-term Fluoride Release was higher in neutral citrate solution than in water. For some formulations the short-term Fluoride Release also was higher in neutral citrate solution than in water suggesting that the polysalt matrix composition could be important in this respect. Significance The Fluoride Release process is due not only to a loss of relatively loosely bound Fluoride in the cement matrix, but also to the Release of strongly bounded Fluoride inducing a long-term Fluoride Release. The effect of citrate on the Fluoride Release process may increase depending on the acid (polyacrylic acid versus copolymers of polyacrylic acid) used for the polysalt formation in the hardening cement. Depending on the competition between the polyacrylate anion and the citrate anion for the metal cation extraction the Fluoride Release process may be retarded.
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Effect of encapsulation on the Fluoride Release from conventional glass ionomers.
Dental materials : official publication of the Academy of Dental Materials, 2002Co-Authors: Roeland De Moor, Ronald VerbeeckAbstract:Abstract Objectives: The aim of the present study is to investigate the effect of the type of encapsulation and the batch on the Fluoride Release of conventionally setting glass ionomer cements Ketac-Fil and Fuji Cap II. Methods: Three capsule types were selected: the capsules of Ketac-Fil and Fuji Cap II, and standard capsules. Six individual series of five cylindrical specimens were made from fresh mixes and leached at 37°C with 25 ml distilled water up to 56 days. A second series of five specimens per formulation in original capsules was made from fresh mixes of another batch. The Fluoride concentration was determined by means of a Fluoride-ion selective electrode. Results: The Fluoride Release profiles of a given glass ionomer formulation generally run parallel regardless of the type of encapsulation. When the amounts of Fluoride Released within the specific formulation were compared as a function of the capsule type, statistically significant differences were only found for Ketac-Fil. Comparing the amounts of Fluoride Released by different batches of a given glass ionomer formulation, statistically significant differences were only found for Fuji Cap II. Significance: The type of encapsulation may affect the Fluoride Release of a given glass ionomer formulation quantitatively, but not qualitatively. Apparently, different batches of the same formulation may result in different amounts of Fluoride Released.
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Fluoride Release of polyacid-modified composite resins with and without bonding agents.
Dental materials : official publication of the Academy of Dental Materials, 2001Co-Authors: Chris Vercruysse, E.a.p. De Maeyer, Ronald VerbeeckAbstract:Abstract 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 (6 mm diameter and 3 mm 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 10 ml ultra-pure water at 37°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.
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Effect of acetic acid on the Fluoride Release profiles of restorative glass ionomer cements.
Dental Materials, 1998Co-Authors: Roeland De Moor, Ronald VerbeeckAbstract:Abstract 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°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 ] I t /( t + t 1/2 )+ β √ t . The parameters ([ F ] I , t 1/2 ) and β 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.
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Fluoride Release process of resin modified glass ionomer cements versus polyacid modified composite resins
Biomaterials, 1998Co-Authors: Ronald Verbeeck, Roeland De Moor, Erna A. P. De Maeyer, Luc Marks, A M J C De Witte, L.m. TrimpeneersAbstract:The Fluoride Release of conventional and resin-modified glass-ionomers is reviewed and compared to that of Fluoride-releasing (polyacid-modified) composite resins. Each formulation displays a typical Fluoride Release profile. The cumulative amount of Fluoride Released is described by [F]c=[F]It/(t+t1/2)+β√t for glass ionomers whether resin-modified or not, whereas for composite resins this quantity is given by [F]c=[F]It/(t+t1/2)+αt. Both equations indicate that two kinetic processes are responsible for the Fluoride Release profiles. The kinetic parameters [F]I,t1/2,βandα depend on the formulation. On the basis of the exchange characteristics for Fluoride, an attempt is made to explain the mechanisms responsible for these Fluoride Release processes.
Roeland De Moor - One of the best experts on this subject based on the ideXlab platform.
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Effect of a neutral citrate solution on the Fluoride Release of conventional restorative glass ionomer cements.
Dental materials : official publication of the Academy of Dental Materials, 2005Co-Authors: Roeland De Moor, Luc Martens, Ronald VerbeeckAbstract:Summary Objectives This study investigates the effect of a neutral citrate solution on the Fluoride Release of 10 acid–base setting glass ionomer cements during 140 days at 37 °C. Methods Five disks of 10 acid–base setting restorative glass ionomers were prepared according to the manufacturer's instructions. These specimens were immersed individually in 25 ml of a 0.01 mol/l citrate solution with pH=7. Over 140 days, the solutions were regularly renewed and the Fluoride concentration eluted during each period was determined with a combined Fluoride ion selective electrode. Results The cumulative Fluoride Release was the result of an initial high Release that ceased after some time and a long-term of low Fluoride Release. The long-term Fluoride Release was higher in neutral citrate solution than in water. For some formulations the short-term Fluoride Release also was higher in neutral citrate solution than in water suggesting that the polysalt matrix composition could be important in this respect. Significance The Fluoride Release process is due not only to a loss of relatively loosely bound Fluoride in the cement matrix, but also to the Release of strongly bounded Fluoride inducing a long-term Fluoride Release. The effect of citrate on the Fluoride Release process may increase depending on the acid (polyacrylic acid versus copolymers of polyacrylic acid) used for the polysalt formation in the hardening cement. Depending on the competition between the polyacrylate anion and the citrate anion for the metal cation extraction the Fluoride Release process may be retarded.
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Effect of encapsulation on the Fluoride Release from conventional glass ionomers.
Dental materials : official publication of the Academy of Dental Materials, 2002Co-Authors: Roeland De Moor, Ronald VerbeeckAbstract:Abstract Objectives: The aim of the present study is to investigate the effect of the type of encapsulation and the batch on the Fluoride Release of conventionally setting glass ionomer cements Ketac-Fil and Fuji Cap II. Methods: Three capsule types were selected: the capsules of Ketac-Fil and Fuji Cap II, and standard capsules. Six individual series of five cylindrical specimens were made from fresh mixes and leached at 37°C with 25 ml distilled water up to 56 days. A second series of five specimens per formulation in original capsules was made from fresh mixes of another batch. The Fluoride concentration was determined by means of a Fluoride-ion selective electrode. Results: The Fluoride Release profiles of a given glass ionomer formulation generally run parallel regardless of the type of encapsulation. When the amounts of Fluoride Released within the specific formulation were compared as a function of the capsule type, statistically significant differences were only found for Ketac-Fil. Comparing the amounts of Fluoride Released by different batches of a given glass ionomer formulation, statistically significant differences were only found for Fuji Cap II. Significance: The type of encapsulation may affect the Fluoride Release of a given glass ionomer formulation quantitatively, but not qualitatively. Apparently, different batches of the same formulation may result in different amounts of Fluoride Released.
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Effect of acetic acid on the Fluoride Release profiles of restorative glass ionomer cements.
Dental Materials, 1998Co-Authors: Roeland De Moor, Ronald VerbeeckAbstract:Abstract 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°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 ] I t /( t + t 1/2 )+ β √ t . The parameters ([ F ] I , t 1/2 ) and β 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.
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Fluoride Release process of resin modified glass ionomer cements versus polyacid modified composite resins
Biomaterials, 1998Co-Authors: Ronald Verbeeck, Roeland De Moor, Erna A. P. De Maeyer, Luc Marks, A M J C De Witte, L.m. TrimpeneersAbstract:The Fluoride Release of conventional and resin-modified glass-ionomers is reviewed and compared to that of Fluoride-releasing (polyacid-modified) composite resins. Each formulation displays a typical Fluoride Release profile. The cumulative amount of Fluoride Released is described by [F]c=[F]It/(t+t1/2)+β√t for glass ionomers whether resin-modified or not, whereas for composite resins this quantity is given by [F]c=[F]It/(t+t1/2)+αt. Both equations indicate that two kinetic processes are responsible for the Fluoride Release profiles. The kinetic parameters [F]I,t1/2,βandα depend on the formulation. On the basis of the exchange characteristics for Fluoride, an attempt is made to explain the mechanisms responsible for these Fluoride Release processes.
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Fluoride Release profiles of restorative glass ionomer formulations.
Dental Materials, 1996Co-Authors: Roeland De Moor, Ronald Verbeeck, Erna A. P. De MaeyerAbstract:OBJECTIVES: The amounts of Fluoride Released by different glass ionomer formulations were compared on the basis of individual Fluoride Release profiles in order to derive the effect of the physical and chemical formulation on the Fluoride Release process. METHODS: The Fluoride Release profiles of each of five specimens of ten glass ionomer cements setting by an acid-base reaction were investigated. The profiles were obtained by determining the amount of Fluoride Released [F] after equilibrating the samples at 37 degrees C in distilled water for 140 d. The [[F],t]-profiles were compared with a Multivariate Data Analysis on the basis of a Principal Component Analysis. RESULTS: The Multivariate Data Analysis reveals that eight of the ten glass ionomers can be classified into four distinct groups. When the cumulative amount of Fluoride Released by each sample, [F]c, is calculated and fitted as a function of time, a regression analysis (r > 0.99) reveals that [F]c for all samples is most adequately represented by [F]c = ([F]l x t)/(t + t1/2) + beta x square root of t, indicating that two kinetic processes are responsible for the Fluoride Release profiles. SIGNIFICANCE: A comparison of the parameters of this equation shows that the physicochemical rationale for the classification of the glass ionomers conforms to differences in the kinetics of these processes which are determined by the qualitative and quantitative chemical composition as well as by the presentation (hand-mixed vs. capsules) of the glass ionomer. From the classification, it becomes apparent that different formulations can result in the same Fluoride Release profiles.
Erna A. P. De Maeyer - One of the best experts on this subject based on the ideXlab platform.
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Fluoride Release process of resin modified glass ionomer cements versus polyacid modified composite resins
Biomaterials, 1998Co-Authors: Ronald Verbeeck, Roeland De Moor, Erna A. P. De Maeyer, Luc Marks, A M J C De Witte, L.m. TrimpeneersAbstract:The Fluoride Release of conventional and resin-modified glass-ionomers is reviewed and compared to that of Fluoride-releasing (polyacid-modified) composite resins. Each formulation displays a typical Fluoride Release profile. The cumulative amount of Fluoride Released is described by [F]c=[F]It/(t+t1/2)+β√t for glass ionomers whether resin-modified or not, whereas for composite resins this quantity is given by [F]c=[F]It/(t+t1/2)+αt. Both equations indicate that two kinetic processes are responsible for the Fluoride Release profiles. The kinetic parameters [F]I,t1/2,βandα depend on the formulation. On the basis of the exchange characteristics for Fluoride, an attempt is made to explain the mechanisms responsible for these Fluoride Release processes.
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Fluoride Release profiles of restorative glass ionomer formulations.
Dental Materials, 1996Co-Authors: Roeland De Moor, Ronald Verbeeck, Erna A. P. De MaeyerAbstract:OBJECTIVES: The amounts of Fluoride Released by different glass ionomer formulations were compared on the basis of individual Fluoride Release profiles in order to derive the effect of the physical and chemical formulation on the Fluoride Release process. METHODS: The Fluoride Release profiles of each of five specimens of ten glass ionomer cements setting by an acid-base reaction were investigated. The profiles were obtained by determining the amount of Fluoride Released [F] after equilibrating the samples at 37 degrees C in distilled water for 140 d. The [[F],t]-profiles were compared with a Multivariate Data Analysis on the basis of a Principal Component Analysis. RESULTS: The Multivariate Data Analysis reveals that eight of the ten glass ionomers can be classified into four distinct groups. When the cumulative amount of Fluoride Released by each sample, [F]c, is calculated and fitted as a function of time, a regression analysis (r > 0.99) reveals that [F]c for all samples is most adequately represented by [F]c = ([F]l x t)/(t + t1/2) + beta x square root of t, indicating that two kinetic processes are responsible for the Fluoride Release profiles. SIGNIFICANCE: A comparison of the parameters of this equation shows that the physicochemical rationale for the classification of the glass ionomers conforms to differences in the kinetics of these processes which are determined by the qualitative and quantitative chemical composition as well as by the presentation (hand-mixed vs. capsules) of the glass ionomer. From the classification, it becomes apparent that different formulations can result in the same Fluoride Release profiles.
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Fluoride Release profiles of restorative glass ionomer formulations.
Dental materials : official publication of the Academy of Dental Materials, 1996Co-Authors: Roeland De Moor, Ronald Verbeeck, Erna A. P. De MaeyerAbstract:Abstract Objectives . The amounts of Fluoride Released by different glass ionomer formulations were compared on the basis of individual Fluoride Release profiles in order to derive the effect of the physical and chemical formulation on the Fluoride Release process. Methods . The Fluoride Release profiles of each of five specimens of ten glass ionomer cements setting by an acid-base reaction were investigated. The profiles were obtained by determining the amount of Fluoride Released [F] after equilibrating the samples at 37°C in distilled water for 140 d. The {[F],t}-profiles were compared with a Multivariate Data Analysis on the basis of a Principal Component Analysis. Results . The Multivariate Data Analysis reveals that eight of the ten glass ionomers can be classified into four distinct groups. When the cumulative amount of Fluoride Released by each sample, [F] c , is calculated and fitted as a function of dime, a regression analysis (r>0.99) reveals that [F] c for all samples is most adequately represented by [F] c = ([F] | .t)/(t+t 1/2 ) + β·√t, indicating that two kinetic processes are responsible for the Fluoride Release profiles. Significance . A comparison of the parameters of this equation shows that the physicochemical rationale for the classification of the glass ionomers conforms to differences in the kinetics of these processes which are determined by the qualitative and quantitative chemical composition as well as by the presentation (hand-mixed vs. capsules) of the glass ionomer. From the classification, it becomes apparent that different formulations can result in the same Fluoride Release profiles.
Edward J. Swift - One of the best experts on this subject based on the ideXlab platform.
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short term Fluoride Release uptake of glass ionomer restoratives
Dental Materials, 1995Co-Authors: Ana M Diazarnold, David C. Holmes, David W. Wistrom, Edward J. SwiftAbstract:Abstract Objectives. The short-term Fluoride Release/uptake of four glass ionomer restoratives was measured and compared to the Fluoride Release after exposure to three commercial Fluoride gels. Methods. Materials tested were: 1) Ketac-Fil (ESPE GmbH); 2) Ketac-Silver (ESPE GmbH); 3) Photac-Fil (ESPE GmbH); and 4) Fuji II LC (GC Corp.). Twenty discs of each material were fabricated and stored in deionized water at 37°C. Initial Fluoride Release was measured at 24 h intervals for 7 d, and 24 h intervals at the end of each week for 5 wk. After 6 wk, samples were divided into groups and each group was treated for 6 min with one of the following commercial Fluoride gels: acidulated phosphate Fluoride (APF), neutral sodium Fluoride (NaF), and stannous Fluoride (SnF2). Control specimens were placed in deionized water. After exposure, Fluoride measurements were carried out at 24 h intervals for 7 d, and 24 h intervals at the end of 2 wk. Fluoride exposure was repeated, and measurements were again recorded over 3 wk. Results. Initial Fluoride Release by all materials was highest during the first 24 h and decreased sharply over the first week. After exposure to APF, Fluoride Release increased significantly for all materials. Exposure to NaF also resulted in increased Fluoride Release for all materials although it was not as high as the increase recorded after exposure to APF. Exposure to SnF2 did not result in significant Fluoride Release by any material. Significance. The results of this study suggest that certain Fluoride gels may replenish Fluoride within some glass ionomers and thus prolong their cariostatic potential.
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Short-term Fluoride Release/uptake of glass ionomer restoratives
Dental materials : official publication of the Academy of Dental Materials, 1995Co-Authors: Ana M. Diaz-arnold, David C. Holmes, David W. Wistrom, Edward J. SwiftAbstract:Abstract Objectives. The short-term Fluoride Release/uptake of four glass ionomer restoratives was measured and compared to the Fluoride Release after exposure to three commercial Fluoride gels. Methods. Materials tested were: 1) Ketac-Fil (ESPE GmbH); 2) Ketac-Silver (ESPE GmbH); 3) Photac-Fil (ESPE GmbH); and 4) Fuji II LC (GC Corp.). Twenty discs of each material were fabricated and stored in deionized water at 37°C. Initial Fluoride Release was measured at 24 h intervals for 7 d, and 24 h intervals at the end of each week for 5 wk. After 6 wk, samples were divided into groups and each group was treated for 6 min with one of the following commercial Fluoride gels: acidulated phosphate Fluoride (APF), neutral sodium Fluoride (NaF), and stannous Fluoride (SnF2). Control specimens were placed in deionized water. After exposure, Fluoride measurements were carried out at 24 h intervals for 7 d, and 24 h intervals at the end of 2 wk. Fluoride exposure was repeated, and measurements were again recorded over 3 wk. Results. Initial Fluoride Release by all materials was highest during the first 24 h and decreased sharply over the first week. After exposure to APF, Fluoride Release increased significantly for all materials. Exposure to NaF also resulted in increased Fluoride Release for all materials although it was not as high as the increase recorded after exposure to APF. Exposure to SnF2 did not result in significant Fluoride Release by any material. Significance. The results of this study suggest that certain Fluoride gels may replenish Fluoride within some glass ionomers and thus prolong their cariostatic potential.
Lennart Forsten - One of the best experts on this subject based on the ideXlab platform.
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Fluoride Release and uptake by glass ionomers and related materials and its clinical effect
Biomaterials, 1998Co-Authors: Lennart ForstenAbstract:The anticariogenic effect of silicate cement is well known and considered a result of Fluoride Release. In several studies a similar Fluoride Release from conventional glass-ionomer cement (GIC) has been established. Therefore, an anticariogenic effect may be predicted from the GICs too. In my studies the Fluoride Release was studied by exposing the test specimens to a continuous flow of running tap water. At certain time periods the specimens were transferred for 1 week in a small amount of deionized water (5 ml). The determination of the Fluoride content of the solution showed the Fluoride Release of the material at that time. There was an initial 'burst' effect of Fluoride Release and then the Release gradually decreased, settling at a constant level. The long-term Release from conventional GICs was shown to remain on the same level for at least 8 years. The amount of the constant Release did not differ much between different brands. Resin-modified GICs Released Fluoride to the same extent and in the similar way as conventional GICs whereas polyacid-modified composites ('compomers') did not show an initial Fluoride 'burst' effect. To study the Fluoride binding ability of GICs, specimens which had been exposed to running water for different periods of time were treated with a 50 ppm Fluoride solution. After this 'recharging' GIC and resin-modified GIC specimens Released more than twice the amount of Fluoride Released before the treatment. The Fluoride treatment had no effect on polyacid-modified composites or on Fluoride-containing composites or on the amalgams. To get an impression of the clinical effect of GICs a questionnaire was handed out to practitioners attending courses in the Nordic countries and in Australia during the period 1991-1992 which resulted in 954 answers. Among other questions, the dentists were asked if they had observed caries and gingival inflammation in association with GIC and composite fillings. According to the opinion of most dentists caries and gingival inflammation had never or only seldom been observed in association with GIC fillings whereas most dentists had observed these complications often in connection with composite restorations.
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resin modified glass ionomer cements Fluoride Release and uptake
Acta Odontologica Scandinavica, 1995Co-Authors: Lennart ForstenAbstract:The aim was to study the short- and long-term Fluoride Release from resin-modified glass ionomer cements (GIC). The aim was also to determine the effect of Fluoride treatment of 9-month-old specime...
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Fluoride Release and uptake by glass ionomers.
European Journal of Oral Sciences, 1991Co-Authors: Lennart ForstenAbstract:Forsten L: Fluoride Release and uptake by glass ionomers. ScandJ Dent Res 1991; 99: 241-5. Abstract - The aim was to study the fiuoride Release 1) from 7 and 15-month-old glass ionomer specimens after treating them wilh 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 fiuoride Release was measured after each of the two periods of time. The fiuoride treated specimens Released more fiuoride 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.