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 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     

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.     

Effect of storage media on the fluoride release and surface microhardness of four polyacid-modified composite resins ("compomers").

OBJECTIVES: The aims of this investigation were to measure the surface microhardness (Vickers) as well as the release of fluoride from four polyacid-modified composite resins (PMC) ("compomers") (Compoglass F, F 2000, Dyract AP, experimental compomer) after storage in various artificial saliva (buffers) including one esterase-buffer. METHODS: Samples were stored for 6 days in de-ionized water, acidic buffer I (pH 4.2), neutral buffer II (pH 7.0), or neutral buffer III (pH 7.0) containing porcine esterase. The specimens were transferred into fresh media every 48 h. Fluoride release was measured every 48 h. Vickers hardness of each five samples of every group was determined before storing the samples in media (baseline) as well as after storage for 24, 48, and 144 h in the various solutions. Dry-stored specimens served as control. RESULTS: The surface microhardness of all PMCs significantly decreased after storage in the various media. No significant differences, however, were found between samples of the same material stored in the various media for 6 days. In general, the highest fluoride quantity was released into the acidic buffer I except for Dyract AP, which segregated similar quantities of fluoride into buffer I and into de-ionized water. More fluoride was released into de-ionized water than into neutral buffers. Further, esterase treatment increased fluoride release from three PMCs. SIGNIFICANCE: Our results suggest that the action of salivary esterases may weaken the surface of polyacid-modified composite resin restorations. As a clinical consequence, wear may be enhanced and load resistance may be reduced. In addition, fluoride release from PMCs may be increased by hydrolytic enzymes in saliva and under acidic conditions.     

Fluoride release, weight loss and erosive wear of modern aesthetic restoratives.

OBJECTIVE: In this investigation, the in vitro sustained fluoride release, weight loss and erosive wear of three conventional glass ionomer cements (Fuji IX, ChemFil Superior, Ketac-Silver), three resin-modified glass ionomer cements (Fuji II LC, Vitremer, Photac-Fil), a polyacid-modified resin composite (Dyract), and a resin composite control material (Z100) were compared. METHODS: The amounts of fluoride released and weight changes were measured for 12 weeks using a fluoride electrode with TISAB III buffer. After 12 weeks, the specimens were recharged with fluoride using 2 mL of 1.23% APF gel. The recharged specimens were assessed for the amounts of fluoride released and weight changes over another 12 weeks. At the end of the experiment, the specimens were examined with SEM and surface profilometry. RESULTS: All materials, with the exception of Z100, showed the highest initial fluoride release rates during the first 2 days, dropping quickly over 2 weeks and becoming largely stabilised after 5 weeks, in an exponential mode. The recharging of the specimens with APF gel caused a large increase in the amounts of fluoride released during the first 2 days only. Analyses for all cements showed strong correlations between mean weight loss and cumulative fluoride release over a 5-week period following the application of the APF gel. SEM and surface profilometry found that roughness increased from the polyacid-modified resin composite to the conventional glass ionomer cements. CONCLUSIONS: APF gel caused erosive wear of the glass ionomer cements especially, and the wear correlated well with the weight losses. To minimise surface erosion, APF gel should not be used on these cements, especially as the recharging effects are transitory.     

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.     

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     

Storage of polyacid-modified resin composites (“compomers”) in lactic acid solution

OBJECTIVES: The aim of this study was to determine the interaction of four polyacid-modified resin composites with aqueous lactic acid solutions, and to compare changes with those for a glass-ionomer cement and a conventional resin composite. METHODS: For each material, namely Compoglass F, Dyract AP, Hytac and Ana Compomer, plus AquaCem (glass-ionomer cement) and Pekafil (conventional composite resin), five cylindrical specimens of 4 mm diameter x 6 mm height were prepared and weighed. They were stored individually in 2.0 cm3 of 0.02 mol l-1 lactic acid solution for 1 week then the pH was determined and the specimens reweighed. The lactic acid solution was replenished, and the specimens were stored for a further week, after which the pH and specimen weights were again measured. This was repeated at 1 week intervals until the specimens were 6 weeks old. Differences were analysed by ANOVA followed by Newman-Keuls post hoc analysis. RESULTS: All four polyacid-modified composites increased the pH of the solutions at all time intervals by at least 0.26 pH units (significant to at least p < 0.01). This effect was similar to that of the glass-ionomer (but significantly less, p < 0.05) while significantly greater (p < 0.05) than that for the composite, Pekafil, which, by contrast, had no effect on pH. The observed rise in pH reduced significantly over time (ANOVA, p < 0.05). After 1 week, all pH changes were accompanied by net reductions in specimen mass, indicating susceptibility to acid erosion. Hytac was significantly more resistant to this erosion than the other materials; conversely, it had the least effect on solution pH. SIGNIFICANCE: These results show that polyacid-modified resin composites neutralise lactic acid in vitro but suffer erosion in the process.     

Fluoride release from esthetic restorative materials with and without adhesive.

OBJECTIVE: The purpose of this in vitro study was to compare the effect of surface coating containing fluoride on patterns and amounts of fluoride release from 5 esthetic restorative materials. METHOD AND MATERIALS: Twelve cylinders of each material were prepared in a plexiglass mold. The experimental groups (n = 6) were coated with 1 layer of fluoridated adhesive resin, Prompt L-Pop, while the control groups (n = 6) remained uncoated. Fluoride release into deionized water was measured on days 1, 2, 3, 7, 14, 21, and 28 using an ion analyzer. Results were evaluated statistically using repeated measure analysis of variance and Duncan test. RESULTS: In the uncoated materials, the highest fluoride-releasing material was a resin composite Ariston pHc (140.468 +/- 9.80) followed by Photac-fil (101.200 +/- 5.56), Ketac-fil (91.098 + 4.69), Hytac Aplitip (5.122 +/- 1.00), and Ecusit (0.310 +/- 0.18). Material-coating interaction was found to be significant, but the effect of surface coating was different for each material. Among the coated materials, conventional glass-ionomer cement Ketac-fil released the highest amount of fluoride (93.326 +/- 10.86), followed by Photac-fil (83.666 +/- 4.72), Ariston pHc (53.862 +/- 7.90), Hytac Aplitip (14.634 +/- 2.35), and Ecusit (1.355 +/- 0.29). CONCLUSION: Application of fluoridated adhesive affected fluoride release from each material in varying magnitudes.     

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).     

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.     

Marginal adaption of Class V restorations with and without "softstart-polymerization"

Polymerization shrinkage causing marginal gap formation is still a major problem in light curing restorations. The aim of the present study was to test the influence of "softstart polymerization" (prepolymerization at a low light intensity followed by a final cure at a high light intensity) on the marginal integrity of polyacid-modified resin and composite resin restorations in Class V cavities using a commercially available curing unit with two defined curing intensities. Sixty standardized Class V cavities were prepared. Twenty cavities at a time were filled either with a composite resin [Spectrum + Prime & Bond 2.1 (SP)], or with polyacid-modified resins [Dyract + Prime & Bond 2.1 (DY); Hytac + OSB Primer (HY)]. Ten fillings of each group were either conventionally cured (40 seconds, 800 mW/cm2), or they were cured with a lower starting intensity (10 seconds, 150 mW/cm2) and then with the full intensity (30 seconds, 800 mW/cm2). Margins were evaluated before and after thermomechanical loading (TCML) by quantitative margin analysis. Microleakage was assessed by dye penetration. The softstart polymerization showed no significant influence on gap formation for each material and interface before and after TCML. Quantitative margin analysis after TCML showed significantly fewer marginal gaps at the enamel/restoration interface for SP (0%) compared to DY (15.5%) and HY (44.5%) using softstart polymerization. At the dentin/restoration interface the corresponding results for gap formation were 29.6% for SP, 8.5% for DY, and 21.0% for HY. These results were not significantly different from each other. Dye penetration was significantly higher for SP at the dentin/restoration interface. SP showed significantly more marginal swelling at the dentin/restoration interface compared to DY. In conclusion, softstart polymerization using a very low starting intensity did not improve the marginal adaptation of polyacid-modified resins or composite resins in Class V cavity preparations. The best marginal adaptation in Class V cavities at the enamel/restoration interface was achieved with SP, using the acid-etch technique. In dentin, however, the polyacid-modified resins showed a superior marginal adaptation.     

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.     

Bond strength of a resin composite to a polyacid-modified resin composite under different conditions.

OBJECTIVE: The aim of this in vitro study was to evaluate the tensile bond strength values between polyacid-modified resin composite ("compomer") and resin composite materials under different conditions. METHOD AND MATERIALS: There were five experimental groups in the study. In group A, resin composite was placed directly on polyacid-modified resin composite surfaces. In group B, bonding agent was applied to polyacid-modified resin composite surfaces and then resin composite was placed on the compomer. In group C, compomer specimens were stored for 1 week and then resin composite was placed directly on these aged compomers. In group D, compomer specimens were again stored for 1 week, and then the bonding agent and resin composite were applied to the compomer surfaces. In group E, the surfaces of aged (1 week) compomers were roughened before the bonding agent was applied and the resin composite was placed on the prepared surfaces. A statistical analysis of the results was made with the Kruskal-Wallis test method. RESULTS: The mean tensile strength values of the groups were as follows: group A = 12.84 MPa; group B = 15.03 MPa; group C = 10.60 MPa; group D = 11.56 MPa; group E = 24.87 MPa. There were statistically significant differences between groups E and A; groups E and C; groups E and D; and groups C and B. CONCLUSION: Mechanical roughening of a polyacid-modified resin composite surface was found to be the most effective factor in increasing the tensile bond strength between an aged compomer and a resin composite.     

Evaluation of a new 2-paste glass ionomer cement

A new 2-paste resin-reinforced glass ionomer cement, Fuji Ortho Band Paste Pak (GC Corporation, Tokyo, Japan), for the placement of orthodontic bands, has been developed for easier handling. The aim of this study was to compare the fluoride release and uptake characteristics of this cement with that of 3 others commonly used to cement orthodontic bands: a conventional resin-reinforced glass ionomer cement, a polyacid-modified composite resin, and a conventional glass ionomer cement. Fluoride release was measured during a 28-day period. After the measurement on day 28, experimental samples were exposed to 1000 ppm sodium fluoride solution for 5 minutes, and fluoride release was then measured for 7 days. Initially, the new 2-paste resin-reinforced glass ionomer cement released the greatest amount of fluoride; the polyacid-modified composite resin released the least initially, and it continued to show the lowest values throughout the study. The fluoride uptake and release values of the new 2-paste resin-reinforced glass ionomer cement were statistically significantly higher than those of the conventional resin-reinforced glass ionomer cement or the conventional glass ionomer cement. The new 2-paste resin-reinforced glass ionomer cement might be a good alternative to conventional products for cementing orthodontic bands.     

In vitro fluoride release from aesthetic restorative materials following recharging with APF gel

In this in vitro study, the fluoride ion release from three more-viscous conventional glass ionomer cements (GICs)--ChemFlex, Fuji IX GP, Ionofil Molar--four polyacid-modified resin composites (compomers)--Dyract AP, Compoglass F, Freedom, F2000--and a hybrid resin composite--Ariston pHc--were compared. The amounts of fluoride release from 3 x 2.7 mm specimens were measured over six weeks using a fluoride ion-selective electrode. After six weeks, the specimens were recharged with 2 ml of 1.23 per cent acidulated phosphate fluoride (APF) gel for four minutes. The recharged specimens were then assessed for the amounts of fluoride release over another six weeks. Statistical analyses were performed using one-way and repeated measures ANOVA. The GICs and Compoglass F showed significantly higher initial fluoride release rates during the first two days (p < 0.05). After the first two days, fluoride release rates from all materials dropped quickly and became essentially stabilized within three-five weeks, in an exponential mode. The recharging of the specimens with APF gel caused a brief, but significant, increase in fluoride release for all materials (p < 0.05), before decreasing to previous comparable rates. Compoglass F released relatively more fluoride, and Ariston pHc relatively less, after APF gel application than before. The lowest total amounts over the study were released by Dyract AP and Freedom. The newer compomers, as well as the newer more-viscous GICs, appear to act as fluoride reservoirs to varying extents.     

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 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).     

Shear bond strength of repaired adhesive filling materials using different repair procedures

PURPOSE: Matrices of adhesive restorative materials and repair procedures may both influence bond strength of repaired adhesive materials. This study examined the bond strength of adhesive filling materials to mature adhesive materials after pretreatment with Co-Jet, Monobond S, and Silibond. MATERIALS AND METHODS: A hybrid composite (Tetric Ceram), a polyacid-modified composite resin (Dyract), and an ormocer (Definite) and their corresponding bonding agents were tested in combination with the repair systems. Restorative materials were placed in molds and polymerized. In group A (control), homologous materials were applied on the polymerized surface directly. In group B, homologous filling materials were placed onto the respective material with the corresponding bonding agent. In group C, adhesive repair filling material was applied after solely pretreating with the repair systems. In group D, the restorative material was applied after pretreatment with the repair systems and application of the corresponding bonding agent. Each subgroup consisted of 20 specimens. The shear bond strength of the samples was measured in a universal testing machine according to the test procedure ISO 10477. RESULTS: The significantly best bond strength of repair filling material on Tetric was achieved by pretreating with Co-Jet followed by application of the corresponding bonding agent (25.5 +/- 5.4 MPa, p < 0.05). A single application of the bonding agent or use of Monobond with bonding agent also yielded bond strengths of 20 MPa or more on Tetric. For Dyract or Definite, bond strengths of 15.5 +/- 5.3 MPa or less were achieved with the different repair procedures. CONCLUSION: Successful pretreatment of hybrid composites for repair can be achieved by application of Co-Jet followed by the corresponding bonding material, whereas sufficient repair of ormocers and polyacid-modified resin composites is limited.     

Fluoride release and uptake by four new fluoride releasing restorative materials

The present study compared the initial fluoride release and release following refluoridation of a conventional glass-ionomer Ketac-Molar (ESPE), a resin-modified glass-ionomer, Vitremer (3M), and two compomers F-2000 (3M) and Hytac (ESPE). Fifteen test specimens were prepared for each brand and immersed in deionized water. The fluoride released was measured every 2 days for 22 days. Refluoridation of the test specimens was done with solutions of 0.02, 0.04 and 0.2% NaF for 5 min on days 22, 30, 38 and 46. The fluoride released from recharged specimens was measured every 2 days until day 54. The fluoride release was highest during the first days after preparation, after which it decreased sharply and then more slowly. The four materials became 'recharged' with fluoride following repeated fluoride exposure in solution, the 0.2% solution being the most effective. From a clinical point of view, the results from this study imply that all the restorative materials tested may act as intra-oral devices for the controlled slow release of fluoride at sites at risk of recurrent caries. Fluoride release and uptake by four new fluoride releasing restorative materials.