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.     

The release of ions by compomers under neutral and acidic conditions

Three commercial compomers have been studied for their interaction with aqueous solutions (i.e. water at pH 5.9 and lactic acid at pH 2.7). Light-cured discs of these materials (12.8 diameter x 1 mm depth; Dyract AP, Compoglass F and F2000) were prepared and stored in 5 cm(3) of either water or lactic acid at pH 2.7. After 1 week, mass changes, pH changes and ion-release were determined. For the specimens stored in water, the effect of maturation under neutral conditions was studied by continuing storage for 3 months, followed by storage in lactic acid for a further week after which ion release and pH change were determined. Student's t-test was used to determine statistical significance of any changes observed. All three cured compomers absorbed water and altered the pH of the solutions, though this was statistically significant only in lactic acid. They were found to release Na, Ca, Sr, Al, Si, P and F ions, with greater amounts being released in acidic conditions than neutral ones. More fluoride was released in acid than in water, but the proportion of free (uncomplexed) fluoride to bound (complexed) fluoride was much lower than in neutral conditions. This was attributed to the formation of strong complexes with aluminium. Maturing specimens for 3 months made very little difference to their interaction with the acid solution, except for the total release of fluoride, which was some two to three greater than from the immature specimens.     

An in vitro study of fluoride release from a resin-modified glass ionomer cement after exposure to toothpaste slurries of different pH

. The aim of the study was to evaluate the fluoride release from an aged resin-modified glass ionomer (Vitremer) after exposure to five toothpaste slurries with different pH values. Cylindrical specimens of the material were leached in de-ionized water for 3 months and then exposed for 30 min daily for 10 days to three dentifrice slurries (20 specimens/group) containing 0.05% fluoride with pH values of 2.6, 5.7 and 8.3 and two non-fluoridated slurries with pH values of 2.5 and 5.7. A neutral NaF solution (0.05% F) was used as a control. During the 30 min exposure time, the fluoride concentration was gradually decreased in order to imitate the clinical situation. Thereafter, specimens were immersed individually in de-ionized water and the fluoride release determined. After the first day of exposure, all groups except one without fluoride (pH 5.7) showed significantly (P<0.05) increased fluoride release. After exposure to the fluoridated toothpaste slurry with pH 5.7, significantly (P<0.05) more fluoride was released compared to the toothpaste slurry with pH 8.3. Low pH (2.5 or 2.6) of the slurry resulted in a significantly (P<0.05) higher fluoride release, regardless of whether it was fluoridated or not. The total amount of fluoride released after exposure to the more acidic fluoride toothpaste slurry was greater than that released from the more acidic non-fluoride toothpaste and the less acidic fluoride toothpaste. Our data indicate that the fluoride release from the resin-modified glass ionomer studied may be in-creased after treament with an acidified NaF-toothpaste. Received: 24 January 2000 / Accepted: 20 July 2000     

Effect of alcoholic and low-pH soft drinks on fluoride release from compomer

PURPOSE: The purpose of this study was to evaluate the amount of fluoride released from compomer restorative materials after immersion in various media. MATERIALS AND METHODS: In this test, four materials were used: three compomers (Dyract, Dentsply, Konstanz, Germany; Compoglass, Vivadent, Schaan, Principality of Liechtenstein; and Xeno, Sankins, Tochigi, Japan) and one resin-modified glass ionomer cement (Fuji II LC, GC, Tokyo, Japan). There were four test solutions: one alcoholic (whiskey), two low-pH drinks (Coca-Cola, orange juice), and one deionized water. Over a period of 60 days, the tested specimens were immersed in the test solution for 3 hours every day, then kept in deionized water. The fluoride released was detected by using a fluoride ion selective electrode connected to a microprocessor ion analyzer. The fluoride ion concentration (ppm) of the test solutions and deionized water was recorded after 1, 2, 3, 4, 7, 30, and 60 days. Electron probe microanalysis was used for surface analysis of the fluoride released. RESULTS: When immersed in low-pH soft drinks, compomer showed a significantly higher fluoride release than when immersed in deionized water (p < .0001). For specimens immersed in Coca-Cola, the fluoride release levels (microgram/cm2, mean +/- SD) at 1, 7, and 60 days for Dyract (91.6 +/- 1.8, 39.3 +/- 3.1, 10.5 +/- 0.9), Compoglass (129.5 +/- 0.9, 66.5 +/- 2.7, 19.0 +/- 0.3), Fuji II LC (147.0 +/- 4.2, 50.8 +/- 3.1, 27.6 +/- 3.0), and Xeno (73.6 +/- 3.2, 27.3 +/- 2.1, 6.6 +/- 0.6) demonstrated the trend of significantly lower releases with time in water solution. Over a 60-day period, materials immersed in 100% orange juice released the highest amount of fluoride, which could be attributable to the erosive effect of the medium. Materials immersed in deionized water released the least amount of fluoride. Among the tested compomers, Compoglass released the most fluoride.     

Effect of Alcoholic and Low-pH Soft Drinks on Fluoride Release from Compomer

Purpose: The purpose of this study was to evaluate the amount of fluoride released from compomer restorative materials after immersion in various media. Materials and Methods: In this test, four materials were used: three compomers (Dyract, Dentsply, Konstanz, Germany; Compoglass, Vivadent, Schaan, Principality of Liechtenstein; and Xeno, Sankins, Tochigi, Japan) and one resin‐modified glass ionomer cement (Fuji II LC, GC, Tokyo, Japan). There were four test solutions: one alcoholic (whiskey), two low‐pH drinks (Coca‐Cola, orange juice), and one deionized water. Over a period of 60 days, the tested specimens were immersed in the test solution for 3 hours every day, then kept in deionized water. The fluoride released was detected by using a fluoride ion selective electrode connected to a microprocessor ion analyzer. The fluoride ion concentration (ppm) of the test solutions and deionized water was recorded after 1, 2, 3, 4, 7, 30, and 60 days. Electron probe microanalysis was used for surface analysis of the fluoride released. Results: When immersed in low‐pH soft drinks, compomer showed a significantly higher fluoride release than when immersed in deionized water (p <.0001). For specimens immersed in Coca‐Cola, the fluoride release levels (pg/cm², mean ± SD) at 1, 7, and 60 days for Dyract (91.6 ± 1.8, 39.3 ± 3.1, 10.5 ± 0.9), Compoglass (129.5 ± 0.9, 66.5 ± 2.7, 19.0 ± 0.3), Fuji II LC (147.0 ± 4.2, 50.8 ± 3.1, 27.6 ± 3.0), and Xeno (73.6 ± 3.2, 27.3 ± 2.1, 6.6 ± 0.6) demonstrated the trend of significantly lower releases with time in water solution. Over a 60‐day period, materials immersed in 100% orange juice released the highest amount of fluoride, which could be attributable to the erosive effect of the medium. Materials immersed in deionized water released the least amount of fluoride. Among the tested compomers, Compoglass released the most fluoride. CLINICAL SIGNIFICANCE The results of this study indicate that, at low pH, compomer restorative materials tend to release more fluoride.     

Effects of APF gel on the physical structure of compomers and glass ionomer cements

This study assessed the effect of an acidulated phosphate fluoride (APF) gel on the surfaces of eight modern esthetic restorative materials. Five specimens each of three high powder: liquid ratio conventional glass ionomer cements (ChemFlex, Fuji IX GP, Ionofil Molar), four polyacid-modified resin composites (compomers) (Compoglass F, Dyract AP, Freedom, F2000) and an alkaline glass filled resin composite (Ariston pHc) were prepared and immersed at 37 degrees C in 2 mL of artificial saliva for six weeks. The aged specimens were then coated with 1.23% APF gel for four minutes, rinsed and again immersed in artificial saliva for another six weeks. The immersed, fresh specimens for each material were then examined with SEM and surface profilometry. After APF gel application, mean surface roughness (Ra) measurements and SEMs showed that roughness increased significantly, generally from the resin composite and compomers to the conventional glass ionomer cements (p < 0.05).     

THE INTERACTION OF POLYACID-MODIFIED COMPOSITE RESINS ("COMPOMERS") WITH AQUEOUS FLUORIDE SOLUTIONS

Objective:

The aim of this study was to investigate how the release of fluoride from two compomers and a fluoridated composite resin was affected by exposure to KF solution.

Material and Methods:

Two compomers (Dyract AP and Compoglass F) and one fluoridated composite (Wave) were prepared as discs (6 mm diameter and 2 mm thick), curing with a standard dental lamp. They were then stored in either water or 0.5% KF for 1 week, followed by placement in water for periods of 1 week up to 5 weeks total. Fluoride was determined with and without TISAB (to allow complexed and decomplexed fluoride to be determined), and other ion release (Na, Ca, Al, Si, P) was determined by ICP-OES.

Results:

Specimens were found not to take up fluoride from 100 ppm KF solution in 24 h, but to release additional fluoride when stored for up to five weeks. Compomers released more fluoride cumulatively following exposure to KF solution (p<0.001), all of which was decomplexed, though initial (1 week) values were not statistically significant for Dyract AP. Other ions showed no variations in release over 1 week, regardless of whether the specimens were exposed to KF. Unlike the compomers, Wave showed no change in fluoride release as a result of exposure to KF.

Conclusions:

Compomers are affected by KF solution, and release more fluoride (but not other ions) after exposure than if stored in water.     

Effects of extraction media upon fluoride release from a resin-modified glass-ionomer cement

Previous studies have shown that various factors such as ionic composition or pH of the extraction medium may significantly influence leaching of components from restorative materials. Therefore, it was the aim of this investigation to determine the release of fluoride from a resin-modified glass-ionomer cement (GIC) following storage in various extraction media, including an esterase buffer. Specimens of the resin-modified GIC, Fuji II LC, were stored for 144 h in deionized water, acidic buffer (pH 4.2), neutral buffer (pH 7.0), and neutral buffer supplemented with porcine liver esterase. Fluoride release into the various media was measured every 48 h over a 6-day period. In addition, activity of porcine esterase in neutral buffer (artificial saliva) was measured for up to 144 h. The data were statistically evaluated by three-way ANOVA using the Student-Newman-Keuls test (P<0.05). It was found that esterase activity in neutral artificial saliva decreased during the first 24 h to approximately 40% of the baseline value and then remained constant for up to 6 days. Fluoride release into the various storage media varied significantly (P<0.05). The highest amounts of fluoride were released into deionized water (30.9 ppm±1.1) and acidic buffer (26.9 ppm±0.7) after 48 h. In addition, significantly more fluoride leached into esterase-containing neutral artificial saliva (6.9 ppm±0.2) than into neutral buffer without enzyme (6.3 ppm±0.2) after 96 h. Our data indicate that fluoride release from the resin-modified GIC investigated may be increased under acidic conditions and by hydrolysis in saliva. Received: 23 July 1998 / Accepted: 7 September 1998     

Effect of APF gel on micromorphology of resin modified glass-ionomer cements and flowable compomers

The purpose of this study was to evaluate the surface micromorphology of resin modified glass-ionomer cements and flowable compomers. In the study two resin modified glass-ionomers and two flowable compomers were used to prepare standardized 20 cylinderic samples. Samples were divided into four groups. Surface treatments with APF gel for experimental groups (group B,C,D) or distilled water as a control (group A) were performed four times. In group B, only APF gel was applied. In group C, after the APF gel application, the samples were immersed into the demineralizing and remineralizing solutions. In group D, before the APF gel application, the buffer solution was applied. The examinations of the surface micromorphology of the materials were made by using scanning electron microscope (SEM). Results showed that in group B all of the materials except Compoglass Flow, and in group C all of the materials showed erratic behaviours. In group D, severe erratic effect (score 2) was obtained on the surfaces of Vivaglassliner and Dyract Flow, and for the others score 1 signals were found. The moderate degradation was obtained by applying of only APF gel on the surfaces of both material groups. The addition of pH circulation caused increasing of micromorphologic changes on the surfaces of all materials. The effect of application of buffer solution on the surfaces before APF gel changed according to the materials. If acidulated fluoride gel is preferred for prophylactic therapy in patients' mouth, for the success, either buffer or neutral fluoride have to be applied on the restored teeth by resin based materials before acidulated fluoride application.     

The recharge of esthetic dental restorative materials with fluoride in vitro-two years' results.

OBJECTIVES: A range of esthetic restorative dental materials are now available to dental clinicians. The aim of this study was to evaluate the relative fluoride recharge potential of a number of these materials in vitro over two years. METHODS: Disc samples (12 mm x 2 mm) of each of the materials were placed into artificial saliva at neutral pH. The materials tested were: two glass ionomers (Chemfil; Ketac-Fil), two resin-modified glass ionomers (Photac-Fil Aplicap; Vitremer), two compomers (Dyract; Compoglass) and two composites (Heliomolar; Concise). At 13 intervals over a two years period the discs were subjected to a 2 min fluoride recharge by exposure to sodium fluoride (500 ppm F). The pre- and post-recharge fluoride release values were determined using an ion sensitive electrode. RESULTS: At all time intervals the post-recharge fluoride release of the materials was significantly different (MANOVA p<0.0001). The mean values for post-recharge fluoride release after two years were: Chemfil 10.3, Ketac 3.0, Vitremer 9.0, Photac-Fil Aplicap 12.1, Compoglass 5.0, Dyract 3.6, Concise 0.3, Heliomolar 0.2 (units = microgF/cm(2)/h). SIGNIFICANCE: Esthetic fillings vary significantly in their capacity to absorb and re-release fluoride. The glass ionomer-based materials displayed a far greater potential for fluoride recharge than the composites, in which the recharge was virtually negligible. Whilst it cannot be assumed that fluoride release is directly proportional to cariostatic potential, these results suggest that, where possible, glass ionomer-based materials should be used in patients who have a high caries rate.     

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.     

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.     

Effects of various storage media on surface hardness and structure of four polyacid-modified composite resins ("compomers")

It was the purpose of this study to determine surface microhardness and structure of four poly-acid modified composite resins ("compomers") after 1-year storage in water and various solutions. Specimens of the compomers Dyract (DY), Compoglass F (CG), an experimental compomer (EC), and of F2000 (F) were stored at 37 degrees C for 1 year in distilled water, acidic buffer (pH 4.2), neutral buffer (pH 7.0), and neutral buffer supplemented with 1.6 u/ml porcine liver esterase. Then the specimens were kept dry for 3 days further. Continuously dry-stored samples (37 degrees C) served as controls. Surface microhardness (Vickers) was read at baseline (prior to wet storage), after 24 h and 144 h, then every 30 days up to 1 year and after the further 3 days of dry storage. Surface roughness (Ra) was determined at baseline, after 3, 6, 9, and 12 months and, finally, after the further 3 days. In addition, randomly selected control and experimental specimens were investigated by SEM. Data were statistically analyzed by a three-factor ANOVA using Scheffé tests (P<0.05). Vickers hardness of all experimental samples dropped significantly due to wet storage (P<0.000) during the first month. However, the type of storage medium did not influence microhardness significantly. Surface roughness was not altered by wet storage except for compomer F, which revealed pronounced surface cracks in the SEM. Altogether, our findings point out that surface microhardness and structure of the investigated compomers were not significantly deteriorated by the tested intraoral conditions, such as humidity, pH-fluctuation, or the action of hydrolytic salivary enzymes.     

Evaluation of weight loss and surface roughness of compomers after simulated toothbrushing abrasion test

This study aimed at analyzing the compomers wear by an "in vitro" toothbrushing abrasion test. The null hypotheses tested were that there would be no differences in weight loss and no significant changes in surface roughness of the compomers after this test. The utilized commercial brands were Dyract (Dentsply), Dyract AP (Dentsply), Compoglass F (Vivadent), Freedom (SDI), F2000 (3M ESPE), which were compared to the two resin composites Z100 (3M ESPE) and Silux Plus (3M ESPE). Ten cylindrical specimens for each commercial brand were prepared with 5mm diameter and 3mm thickness. An appropriate machine with soft bristle tips containing dentifrice solution and deionized water was used. A total of 100,000 brushing cycles were performed. The amount of weight loss was measured by the percentage alteration between the initial (before toothbrushing) and final weight (after toothbrushing), measured by a Sartorius analytical balance. The surface roughness change was determined by the percentage difference between initial and final means after 5 tracings by a T 1000 Hommel Tester roughness meter on the specimen's surfaces before and after toothbrushing abrasion test. The statistical analysis (Students paired t-test, ANOVA and Tukey, á=0.05) showed that all materials presented statistically significant weight loss and roughness increase after abrasion test. All compomers presented higher weight loss than resin composites. Freedom and Dyract AP presented the lowest weight loss among compomers. F2000 presented the worst abrasion resistance, without statistical differences with Dyract. For roughness changes, Dyract, Dyract AP, Z100, Compoglass F and Silux Plus showed the lowest surface roughness alteration, in increasing order, without statistical differences between them. Freedom was the statistically roughest material of the study.     

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).     

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     

Effects of daily fluoride exposures on fluoride release by glass ionomer-based restoratives

It is well documented that glass ionomer cements absorb and release fluoride following single fluoride exposures. This study examined fluoride release among three glass ionomer-based restorative materials following multiple daily exposures to three topical fluoride regimens. Using a Delrin mold, 32 cylindrical specimens, each of a glass ionomer (Ketac-Fil), resin-modified glass ionomer (Photac-Fil) and polyacid-modified resin (Dyract AP) were created. Each specimen was subjected to one of four daily treatments (n = 8): (1) no fluoride treatment (control); (2) application of a fluoride dentifrice (1000 ppm) for one minute once daily; (3) application of the same dentifrice for one minute twice daily; (4) the same regimen as (3), plus immersion in a 0.05% sodium fluoride (NaF) mouth rinse (225 ppm) for one minute immediately following the second dentifrice application. Each specimen was suspended in a polyethylene test tube containing 1.0 ml demineralizing solution (pH 4.3) at 37 degrees C for six hours, then transferred to a new test tube containing 1.0 ml remineralizing solution (pH 7.0) at 37 degrees C for 18 hours. Fluoride treatments were completed at the time of transfer daily for seven days. Media solutions were buffered with equal volumes of TISAB II; fluoride levels were measured using a digital ion analyzer and fluoride electrode. Fluoride release decreased significantly from Day 1 to Day 3 for all materials regardless of fluoride treatment (Repeated Measures ANOVA, Tukey HSD, p < 0.05). All specimens released significantly more fluoride in demineralizing solution than in remineralizing solution. For Days 2-7, Treatment 4 produced greater fluoride release than both the control and Treatment 2 for all three materials (p < 0.05); For each material, the fluoride release produced by Treatments 3 and 4 was statistically similar on most days throughout the study. By Day 7, Photac-Fil demonstrated both the greatest total fluoride release and the greatest rechargability, followed by Ketac-Fil and Dyract AP. Although subsequent daily fluoride release never approached that of Day 1, increasing daily fluoride exposures enhanced fluoride release for all three restorative materials.     

Prevention of erosion and abrasion by a high fluoride concentration gel applied at high frequencies

The aim of this study was to determine maximum attainable protection of enamel from erosion and erosion abrasion using a highly fluoridated gel with and without additional fluoride from toothpaste. Thirty-six bovine enamel specimens were subjected to six erosive attacks per day (1% citric acid with pH 2.3 for 30 s), while the rest of the day the specimens were in artificial saliva. There were four treatment groups (9 specimens in each group): fluoride-free toothpaste/saliva slurry twice daily (group T0), fluoride-containing toothpaste/saliva slurry twice daily using 1,250 ppm F toothpaste (group TF), fluoride-containing toothpaste/saliva slurry twice per day plus application of a highly fluoridated gel (12,500 ppm F) twice a day for 120 s (group 2F) and a group with gel application 8 times a day (group 8F). Additionally, half of each specimen in all groups was subjected to brushing abrasion during application of the toothpaste/saliva slurry. Brushing abrasion alone led to no observable enamel loss measured with profilometry. After 14 days of cycling of erosion without toothbrushing abrasion, high-fluoride gel application 2 or 8 times daily showed significantly less enamel loss (median 24/19 microm) than with toothpaste with or without fluoride (41/45 microm). After 14 days of cycling of erosion and toothbrushing abrasion, gel application 2 or 8 times daily (33/29 microm) showed significantly less enamel loss than toothpaste with or without fluoride (57/62 microm). We conclude that a highly fluoridated acidic gel is able to protect enamel from erosion and toothbrushing abrasion while fluoridated tooth paste provides little protection.     

Fluoride uptake in dentin with and without simulating dentinal fluid flow

The aim of the present study was to compare fluoride uptake of dentin with and without simulating dentinal fluid flow. Eighty-five dentinal discs were prepared from retained human molars. Seventeen discs were used to assess baseline fluoride content (controls). Sixty-eight discs were evenly distributed among two experimental groups and were fixed for 24 h in a two-chamber device allowing for simulating dentinal fluid flow. Thirty-four samples were treated with dentifrice slurry containing a low fluoride concentration (Elmex, dilution 1:5); the remaining discs were treated with a solution of a high fluoride concentration (Elmex Fluid). For the perfused group, each of the 17 discs of the high and low concentration fluoride groups were constantly perfused during the experiment. The remaining fluoridated specimens were not perfused. All specimens were assayed for KOH-soluble fluoride and structurally bound fluoride. Structurally bound fluoride was determined in three successive layers of 20 μm each. Uptake of KOH-soluble fluoride was significantly higher in the specimens fluoridated with Elmex Fluid compared to the samples treated with the dentifrice slurry. The uptake of KOH-soluble fluoride was not influenced by perfusion of the dentinal discs. However, perfusion resulted in lower acquisition of structurally bound fluoride in the samples treated with the dentifrice slurry. After application of Elmex Fluid, no significant difference was found in the amount of structurally bound fluoride between the perfused specimens and non-perfused samples. It is suggested that further studies on fluoride uptake in dentin should use a model simulating outward dentinal fluid flow. Received: 4 November 1996 / Accepted: 26 June 1997     

Fluoride release and antibacterial properties of new-generation tooth-colored restoratives

The aim of this study was to compare the amounts and pattern of fluoride release and antibacterial properties of new-generation restoratives over a 35-day period. Materials evaluated included fluoride-releasing composites (Tetric, Experimental X), compomers (Dyract, Compoglass), and a resin-modified glass-ionomer cement (Fuji II LC). A conventional glass ionomer (Fuji II Cap) was used as a control for fluoride-release testing. Five samples of each restorative material were evaluated for daily fluoride release over a 35-day period by means of ion chromatography. Ranking of materials from least to greatest total fluoride release over 35 days was as follows: Tetric < Experimental X < Dyract < Fuji II LC < Compoglass < Fuji II Cap. Fuji II Cap had significantly greater fluoride release than all other materials evaluated. Fuji II Cap, Fuji II LC, and Compoglass had similar patterns of fluoride release characterized by a high initial release that was many times that released later. The fluoride-releasing composites evaluated stopped releasing fluoride by day 14. Antibacterial testing was conducted using the agar diffusion inhibitory test. Five samples of each restorative were assessed at baseline and weekly intervals up to 35 days. The microorganisms used were Lactobacillus casei, Streptococcus mutans, and Streptococcus sobrinus. IRM, a zinc oxide/eugenol cement, was used as the baseline control. None of the restorative materials evaluated affected the growth of L casei, S sobrinus, or S mutans at all time periods including baseline, where fluoride was detected in the agar beneath the specimen disks. There was no correlation noted between fluoride-release potential and antibacterial properties.