Fluoride release from varnish-coated silicates and from cavity liners and fissure sealants

abstract — The fluoride release of varnish-coated silicates and liners and sealants was studied by measuring the uptake of the released fluoride by synthetic hydroxyapatite. Silicate specimens were made and coated with cavity varnish. The specimens were shaken in solution with the apatite for 7 weeks. The apatite was analyzed for fluoride each week and the specimens were then transferred to a fresh solution with new apatite. The varnish reduced the fluoride release during the first three weeks, but after that time the release from the varnish-coated specimens was the same as that from the uncoated specimens. The release from the liners and sealants was studied by coating composite resin specimens with the material. The resin contained no fluoride. The specimens were shaken in solution with apatite and the fluoride uptake was measured each week in the same manner as for the silicate specimens. The liners showed an initial release of fluoride. When the two different sealants were applied as two layers, only one of the brands showed initial release of fluoride. Five layers of sealant resulted in an initial release from both brands.     

Fluoride release from a fluoride-containing amalgam and two luting cements.

The release of fluoride from an amalgam and two luting cements, silicophosphate and polycarboxylate, was studied by shaking test specimens in a solution with hydroxyapatite, and measuring the fluoride taken up by the apatite. The initial release was significant for all three materials. After 1 week the amalgam released only minor amounts of fluoride, whereas the cements continued to liberate fluoride during the 5-week observation time to the same extent as silicates in earlier studies.     

Fluoride release from a fluoride-containing amalgam and two luting cements

abstract – The release of fluoride from an amalgam and two luting cements, silicophosphate and polycarboxylate, was studied by shaking test specimens in a solution with hydroxyapatite, and measuring the fluoride taken up by the apatite. The initial release was significant for all three materials. After 1 week the amalgam released only minor amounts of fluoride, whereas the cements continued to liberate fluoride during the 5-week observation time to the same extent as silicates in earlier studies.     

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

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.     

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     

Fluoride release from a glass ionomer cement

abstract – The release of fluoride from a glass ionomer cement (ASPA®) was. compared with that from a silicate cement. Test specimens were shaken in a solution with hydroxyapadte for 7 weeks. The solution was changed every week and the fluoride taken up by the hydroxyapatite measured. The specimens released considerably more fluoride during each of the first 2 weeks than during each of the subsequent 5 weeks. The continued release did not decrease very much with time. Slightly more fluoride was released from the glass ionomer cement than from the silicate.     

19F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel

Solution chemical and 19F magic angle spinning-nuclear magnetic resonance (MAS-NMR) methods have been utilized to study the effects of fluoride dose, fluoridating pH, and mineral surface area on the dynamics of fluoride reactivity with hydroxyapatite and powdered human dental enamel in vitro. Both solution chemical fluoride uptake and NMR measurements demonstrated that the reaction products of ionic fluoride with apatite include mixtures of FAP, FHAP, and CaF2, with increased amounts of CaF2 promoted by increased F concentration or decreased pH. NMR analysis showed FAP or FHAP as a reaction product of fluoride uptake under all conditions, regardless of whether CaF2 was formed, unambiguously demonstrating fluorite as an additive rather than substitute form of F reactivity. pH stat measurements demonstrated the release of OH- during F reactivity with apatites corresponding to ion exchange formation of FAP/FHAP or dissolution/reprecipitation formation of CaF2. Phosphate release into solution accompanied fluoride uptake under all conditions, including regions where ion exchange predominated. Whereas powdered dental enamel demonstrated fluoride uptake behavior similar to that of synthetic apatite, the resulting reaction products differed as analyzed by 19F MAS-NMR.     

Fluoride release from a glass ionomer cement.

The release of fluoride from a glass ionomer cement (ASPA) was compared with that from a silicate cement. Test specimens were shaken in a solution with hydroxyapatite for 7 weeks. The solution was changed every week and the fluoride taken up by the hydroxyapatite measured. The specimens released considerably more fluoride during each of the first 2 weeks than during each of the subsequent 5 weeks. The continued release did not decrease very much with time. Slightly more fluoride was released from the glass ionomer cement than from the silicate.     

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).     

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.     

Effect of CaF2 content on rate of fluoride release from filled resins

Information on the time-dependent release of fluoride from filled resins containing fluoride particles as a function of particle content and solution pH is limited. This study characterized the fluoride ion release from filled resins containing CaF2 particles as a function of filler content and pH. Urethane dimethacrylate and triethylene glycol dimethacrylate resins were used to make filled-resin disks containing 9.09, 23.08, or 33.33 mass% CaF2 filler. Fluoride ion release for the 9.09 mass% concentration was independent of pH. Increasing the filler content from 9.09 to 33.33 mass% increased the fluoride release rate in pH 4.0 buffer solution, because of greater surface degradation. Fluoride ion release from disks stored in pH 6.0 buffer solutions occurred mainly by diffusion from disk surfaces, while fluoride release from disks in pH 4.0 buffers was controlled by diffusion from disk surfaces and degeneration of the resin matrix, which exposed more CaF2 particle surface area.     

Fluoride release/uptake of glass-ionomer cements and polyacid-modified composite resins

The aim of this study was to investigate the fluoride release and fluoride recharge behaviors of two conventional glass-ionomer cements (GICs) and two polyacid-modified composite resins (PMCRs) after exposure to mouthwash and toothpaste. Fluoride released from the materials was measured at 1st, 2nd, 3rd, 4th, 7th, 14th, 21st, and 28th days. At 28th day, the specimens were divided into three groups. Specimens in the control group were stored in deionized water. For the other two groups, the specimens were exposed to 0.05% NaF solution and fluoridated toothpaste for one month. After refluoridation, fluoride amount was measured at 30th, 31st, 32nd, 36th, 44th, 52nd, and 60th days. All materials released fluoride. The highest amount of fluoride was obtained during the first 24 hours, and there was a statistically significant difference between the amounts of fluoride released from GICs and PMCRs (p < 0.0001). After exposure to mouthwash and fluoridated toothpaste, all materials were recharged and continued releasing fluoride. While the amount of fluoride release from the materials increased after reflouridation, the increase was higher in GICs.     

Fluoride release and uptake characteristics of aesthetic restorative materials

The aims of this study were firstly to investigate the fluoride-releasing characteristics of two composite resins (Tetric and Valux Plus), two polyacid-modified resin composites (Compoglass and Dyract), and conventional glass-ionomer cement (Ceramfil beta). The second aim was to assess the fluoride uptake and subsequent release from the same range of materials. Fifteen discs (6 mm diameter and 1.5 mm height) were prepared for each material. Each disc was immersed in 4 ML of deionized water within a plastic vial. The release of fluoride was measured daily at 1, 2, 3, 4, 5, 15, 30 and 60 days. After daily fluoride release was measured for 60 days, samples were refluoridated in 1000-ppm sodium fluoride (NaF) solutions (pH 6.6) for 10 min and fluoride release was measured daily for a total of 5 days. The release of fluoride from aesthetic restorative materials was measured by using specific fluoride electrode and an ionanalyser. Results were statistically analysed by two-way repeated measure ANOVA and Duncan's multiple range test. The results revealed that all fluoride-containing materials (Ceramfil beta, Compoglass, Dyract, Tetric) released fluoride initially and the release was greatest at the first day. At any time during the test period Ceramfil beta released the most and Valux Plus did not release any detectable fluoride (P < 0.01). Sample exposures to 1000 ppm NaF solution increased the 24-h fluoride release from all fluoride-containing materials. This difference lasted only 24-48 h after exposure. Ceramfil beta had a tendency to recharge not seen with the other materials (P < 0.05).     

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/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.     

The role of implants in orthodontics

Abstract

This study was concerned with an evaluation of fluoride release from commercially available orthodontic bonding composite resins, known as Reliance® and Mirage Dual Cure®, which are claimed to release ionic floride. Forty-eight premolar teeth had brackets bonded with four different composite resins—Mirage Dual Cure®, Reliance®, Right-on® and Heliosit®. They were then immersed in a demineralizing solution. The amount of fluoride released from the composites into the solution was measured. The results indicated that Mirage Dual Curereg; released statistically significant amounts of fluoride over the first 2 days. A similar pattern was noted with Reliance® albeit releasing a lesser amount. From the third day onwards, fluoride release levelled out to concentrations similar to those of the two control materials, Right-on® and Heliosit®(i.e. 0·09 ppm). Fluoride-releasing composite resins, therefore, failed to demonstrate any potential long-term fluoride release within the ex vivo model. Even in the short term, the amount of fluoride released was very small.     

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 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.     

Properties of fluoride-releasing light-activated resin cement.

OBJECTIVES: Fluoroaluminosilicate glass and poly(acrylic acid) in small water phase was incorporated into resin composite cements to reduce or prevent secondary caries around luted restorations. The purpose of this study was to investigate the physical properties and the amounts of fluoride released from four types of visible light-activated resin cements. METHODS: A powder was composed of silanized SiO2 filler and 4.5 wt.% (G-4.5), 9.5 wt.% (G-9.5) or 19.5 wt.% (G-19.5) fluoroaluminosilicate glass and 0.5 wt.% reducing agent. The 45.25 wt.% triethylene glycol dimethacrylate (TEGDMA), 45.25 wt.% 2-hydroxyethyl methacrylate (HEMA), 9 wt.% poly(acrylic acid) solution in water and 0.5 wt.% camphorquinone were contained in a liquid. The powder and liquid were mixed at a 3:1 ratio by weight and the three types of specimen disks were cured using a photo-curing lamp. The TEGDMA-based composite cement was used as control (G-0). The specimens were immersed in water at 37 degrees C for 24 h or 6 months and compressive strength (CS) and diametral tensile strength (DTS) were evaluated for the four experimental materials. Disks prepared from the four resin cements were also immersed in deionized distilled water at 37 degrees C, and the fluoride released was measured over a period of 24 weeks. RESULTS: G-9.5 specimens showed almost the same CS and DTS as G-4.5 and G-0 specimens and significantly higher values for both parameters than G-19.5 specimens after 6 months of water storage. The amount of fluoride released from the three fluoride-containing resin cements continued to increase over the entire experimental period. The fluoride release rates of G-9.5 and G-19.5 resin cements were almost the same and were significantly greater than that of the G-4.5 resin cement. SIGNIFICANCE: G-9.5 containing 9.5 wt.% fluoroaluminosilicate glass may be a clinically useful resin cement due to its favorable physical properties and fluoride release.