7/28/2019 1.Attar, 2002

1/9

Fluoride release and uptake characteristics of aesthetic

restorative materials

N . A T T A R & A . O N E N Faculty of Dentistry, Department of Conservative Dentistry, University of Hacettepe, Ankara, Turkey

SUMMARYSUMMARY 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 glassionomer

cement (Ceramfil b). The second aim was to assess

the fluoride uptake and subsequent release from thesame range of materials. Fifteen discs (6 mm diam-

eter and 15 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 meas-

ured for 60 days, samples were refluoridated in

1000-ppm sodium fluoride (NaF) solutions (pH 66)

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 Duncans multiple

range test. The results revealed that all fluoride-

containing materials (Ceramfil b, Compoglass,

Dyract, Tetric) released fluoride initially and the

release was greatest at the first day. At any timeduring the test period Ceramfil b released the most

and Valux Plus did not release any detectable

fluoride (P < 001). Sample exposures to 1000 ppm

NaF solution increased the 24-h fluoride release

from all fluoride-containing materials. This differ-

ence lasted only 2448 h after exposure. Ceramfil b

had a tendency to recharge not seen with the other

materials (P < 005).

KEYWORDS:KEYWORDS: glassionomer cement, polyacid-modi-

fied resin composite, composite resin, fluoride

release, fluoride uptake

Introduction

Replacement of restorations because of secondary caries

is a continuing problem in restorative dentistry. The

ability of a restorative material to resist secondary caries

and microleakage at its margins will, to a great extent,

determine whether a restoration will succeed or fail

(Dionysopoulos et al., 1998).

Development of an ideal restorative material, thatprovides a permanent seal with tooth structure, has

been thwarted by complicating factors present in the

oral environment: changes in intraoral temperature

(thermal expansion), solubility of certain restorative

materials in saliva and change in pH (Olsen et al., 1989;

Donly & Ingram, 1997). Consequently, increased

emphasis has been placed on developing restorative

materials with anticariogenic properties.

Fluoride has demonstrated anticariogenic effects and

this beneficial effect on the human dentition has led to

the examination of available fluoride in a host of dental

materials (Rawls & Zimmermann, 1983; Skartveit, Tveit

& Extrand, 1985; Olsen et al., 1989; Forsten, 1991;

Donly & Ingram, 1997; Dionysopoulos et al., 1998).

Glassionomer cements were first introduced to the

dental profession by Wilson and Kent in 1972. Their

main characteristics are an ability to chemically bond toenamel and dentine with insignificant heat formation

or shrinkage; biocompability with the pulp and perio-

dontal tissues; fluoride release producing a cariostatic

and antimicrobial action (Rawls & Zimmermann, 1983;

Skartveit et al., 1985; Olsen et al., 1989; Forsten, 1991;

Donly & Ingram, 1997; Dionysopoulos et al., 1998; Hse,

Leung & Wei, 1999). Many investigators have demon-

strated the ability of glassionomer to increase the

2002 Blackwell Science Ltd 791

Journal of Oral Rehabilitation 2002 29; 791798

7/28/2019 1.Attar, 2002

2/9

fluoride content in enamel and dentine adjacent to

restorations (Retief et al., 1984; Forss & Seppa, 1990;

Skartveit et al., 1990). The uptake of fluoride would

increase its resistance to acid demineralization and

prevent caries formation around restorations (Retief

et al., 1984; Hicks, Flaitz & Silverstone, 1986; Forss &

Seppa, 1990; Skartveit et al., 1990; Tyas, 1991; Varpio &

Noren, 1994; Donly & Ingram, 1997; Dionysopoulos

et al., 1998). Fluoride release from glassionomers also

has an antimicrobial action against Streptococcus mutans

in plaque (Seppa, Torppa-Saarinen & Luoma, 1992;

Benelli et al., 1993; Seppa, Korhonen & Nuutinen,

1995).

In the late 1980s and early 1990s, a couple of

so-called light cured glassionomers were released in

the market. From a chemistry point of view there are

two different routes towards these hybrid materials

(Guggenberger, May & Stefan, 1998). These includethe resin-modified glassionomer cements and the

polyacid-modified resin composites (compomers).

Resin-modified glassionomer materials were basically

formed by adding methacrylate derivatives to the

glassionomer formula. Both laboratory and clinical

research has clearly demonstrated the ability of the

resin-modified glassionomers to release fluoride

(Momoi & McCabe, 1993; Forsten, 1995; Burgess

et al., 1996; De Araujo et al., 1996; Tam, Chan &

Yim, 1997). The fluoride release from and uptake by

the resin-modified products was higher than or the

same as that of conventional glassionomers (Momoi

& McCabe, 1993; Forsten, 1995; Burgess et al., 1996;

De Araujo et al., 1996; Tam et al., 1997). Compomer

means that the material possesses a combination of the

characteristics of both composites and glassionomers,

but actually it shows minimal glassionomer reactions

(Suljak & Hatibovic-Kofman, 1996; Guggenberger et

al., 1998). Polyacid-modified resin composites were

formed by adding acidic polymers to the original

methacrylate resin matrix. Compomer is being marke-

ted for use as a restorative alternative to glassionomer

cements.Composite resin restorations are in constantly

increasing demand. However, these restorations have

been associated with the occurrence of marginal

secondary caries relating mainly to marginal leakage

and plaque retention (Van Dijken, 1986; Wilson,

Wilson & Smith, 1988). Studies of the fluoride-

releasing properties of composite resins indicate a

long-term release of fluoride, although the amount

released is low in comparison with that of the glass

ionomers (Swift, 1989; Young et al., 1996).

In vitro studies have also shown the ability of

conventional glassionomer materials and resin-

modified glassionomer cements to take up fluoride

and subsequently release it again (Hatibovic-Kofman &

Koch, 1991; Creanor et al., 1994, 1995; Forsten, 1995;

Suljak & Hatibovic-Kofman, 1996; Young et al., 1996).

There have, however, been few studies into the long-

term fluoride release from the polyacid-modified resin

composites and fluoride-releasing composite resins.

Forsten (1998) has measured both release and uptake

from both types of materials. It was mentioned that the

fluoride treatment had no effect on polyacid-modified

composites or fluoride containing composites or the

amalgams.

The aims of this study were firstly to investigate the

fluoride-releasing characteristics of two composite res-ins, two polyacid-modified resin composites (compo-

mers) and conventional glassionomer cement. The

second aim was to assess the fluoride uptake and

subsequent release from the same range of materials.

Materials and methods

The five aesthetic restorative materials were used in this

study and their characteristics are listed in Table 1. Two

of the materials used were composite resins: one of

them was a non-fluoride-releasing composite resin

Valux Plus*, and the other was fluoride-releasing

composite resin Tetric. The other two were the

polyacid-modified resin composites Compoglass and

Dyract. The last one was the conventional glass

ionomer cement, Ceramfil b.

Sample preparation

Fifteen test samples of each material were in the form of

round disc-shaped samples, 6 mm in diameter and

15 mm thick made using Teflon moulds, placed

between two glass plates. All restorative materials wereprepared according to the manufacturers instructions

using the scoops provided. The light cured materials

(Compoglass, Dyract, Tetric and Valux Plus*) were

cured on both sides with a Translux EC Kulzer light

*3M, Malakoff, France.Vivadent Ets, Schaan, Liechtenstein.Dentsply\De Trey, Konstanz, Germany.EC Kulzer & Co, GmbH D-6383 Wehrheim/TS Germany.

N . A T T A R & A . O N E N792

2002 Blackwell Science Ltd, Journal of Oral Rehabilitation 29; 791798

7/28/2019 1.Attar, 2002

3/9

source for 30 s. Ceramfil b was chemically setting.

Samples were weighed in order to verify standardization

within each material test group (001). The samples

were stored at 100% relative humidity for 24 h.

Initial fluoride release

Each sample was placed in a polyethylene test tubes

filled with 4 mL of deionized water. The polyethylene

test tubes were incubated for 24 h at 37 C. Following

incubation of 24 h, the samples were grasped with

clean metal forceps and rinsed with 1 ML deionized

water over the original holding tube, thus collecting the

rinse water in that tube. Each disc was transferred to a

new polyethylene test tube containing 4 mL deionized

water and stored at 37 C.

Fluoride release was determined at 1, 2, 3, 4, 5, 15, 30

and 60 days after buffering the solution with equal

volumes of total ionic strength adjustment buffer

(TISAB). Fluoride release was measured with a fluoride

ion specific electrode (Orion 96-09 electrode) and an

ionanalszer (Orion EA 940). Data concerning fluoride

was recorded in parts per million (ppm). The electrode

was previously calibrated with standards whose molar-

ity spanned the actual concentrations of fluoride to be

measured (001, 01, 05, 10, 50, 100, 200 and

300 ppm). The fluoride concentration was determined

by adding 5 mL TISAB to each 5 mL sample solution.

Fluoride release after exposure to sodium fluoride (NaF)

Following 60 days of initial fluoride release, samples

from each product were exposed to a standard solution

containing 1000 ppm fluoride ion made from

526 mmol L1 NaF. After copious rinses in deionize

water, each sample was returned to a container filled

with 4 mL of fresh deionized water and incubated.

Fluoride release was measured daily for a total of 5 days.

Statistical analysis

Two-way repeated measure analysis of variances

(ANOVAs) were then performed to compare types ofmaterials for each time point. Also two-way repeated

measure ANOVAs were performed to compare time

points. Statistical analysis of two-way repeated measure

ANOVAANOVA on restorative material versus time revealed

statistically significant difference, so we examined con-

sequent differences between mean values. A one-way

ANOVAANOVA was performed to mean difference values of

each five groups. Duncans multiple range test were

performed to identify group differences for each ANOVA.

ResultsFluoride release (ppm) at days 1, 2, 3, 4, 5, 15, 30, 60

and fluoride release after recharging at days 1, 2, 3, 4

and 5 are presented in the Table 2.

An analysis of two-way repeated measure ANOVA

indicated significant differences in fluoride release

among all five materials (F 647208, P < 001).

There were statistically significant differences between

all the groups. The conventional glassionomer cement

(Ceramfil b) was significantly higher than all other

groups, at any time during the test period. Ceramfil b

released the most, and Valux Plus did not release anydetectable fluoride.

Statistical analysis of two-way repeated measure

ANOVAANOVA on restorative material versus time revealed

statistically significant difference (F 103076,

P < 001). All fluoride containing materials released

most fluoride after the first 24 h and this fluoride

release continued over the entire 60 days testing

period. Initial fluoride release decreased with time.

Table 1. Materials tested for fluoride release

Restorative

material Material class Manufacturer Batch No.

Ceramfil b Conventional glassionomer cement PSP Belvedere, Kent, UK 0694236

Compoglass Polyacid-modified resin composite Vivadent Ets, Schaan, Liechtenstein 800647

Dyract Polyacid-modified resin composite Dentsply\De Trey, Konstanz, Germany 9511060Tetric Fluoride-releasing composite resin Vivadent Ets, Schaan, Liechtenstein 618661

Valux Plus Non-fluoride-releasing composite resin 3M, Malakoff, France 70-2010-1302-9

Orion Research Inc., Beverly, MA, 01915-6199, USA.

F L U O R I D E R E L E A S E A N D U P T A K E 793

2002 Blackwell Science Ltd, Journal of Oral Rehabilitation 29; 791798

7/28/2019 1.Attar, 2002

4/9

Statistical analysis of two-way repeated measure

ANOVAANOVA on restorative material versus time revealed

significant difference so we examined consequent

differences between mean values. Differences between

groups are shown in Table 3. There was statistically

significant difference between Ceramfil b compared

with all other groups (P < 005).

Tables 2 and 3 shows the effects of exposures to

1000 ppm NaF solution. The first day after exposure

there was an increase in fluoride releasing from all

fluoride containing materials. This lasted for only

2448 h after exposure. Ceramfil b had a tendency to

recharge not seen with the other materials. There were

significantly differences after exposure to NaF between

Compoglass and Tetric at day 1day 60 and day 2day

1 and also between Compoglass and Valux Plus at day

1day 60 and day 2day 1. There was no statistically

significant difference between the polyacid-modifiedresin composite and between the composite resin with

regard to exposure to NaF or not (Table 3).

Figure 1a shows the fluoride release of Ceramfil b

from day 1 to day 60 on the basis of the average of the

15 samples. Figure 1b shows the initial fluoride release

of test materials except Ceramfil b from day 1 to day 60,

on the basis of the average of the 15 samples. Figure 2a

shows the fluoride release from Ceramfil b after

exposure to 1000 ppm NaF solution. Figure 2b shows

fluoride release from the other test materials after

exposure to 1000 ppm NaF solution.

Discussion

There were some differences in fluoride release among

the products, and they could represent a valid param-

eter to guide the selection of a material for specific

clinical situations. Kan, Messer & Messer (1997)

suggested that each individual product should be

independently tested to evaluate the amount of fluor-

ide that can released.

Fluoride release from glassionomer appears to

be much greater than from either fluoride contain-ing amalgam or composite (Forsten, 1990). However,

glassionomer cements are not widely used as a

restorative material. Their lack of acceptance may be a

result of their technique sensitivity to moisture, low

mechanical strength and wear resistance (Burgess et al.,

1996; Guggenberger et al., 1998). The fluoride release

of conventional glassionomer cements has been

attributed to acidbase setting reactions involvingTable

2.

Fluori

dere

lease

from

materia

lsteste

d(ppm)(meanan

ds.

d.)

Groups

Day1

Day2

Day3

Day4

Day

5

Day15

Day30

Day60

Day1

Day2

Day3

D

ay4

Day5

Ceram

filb

27

532

1314

3

92

1010

900

956

860

665

97

0

624

880

512

530

541

810

40

10

841

114

230

523

330

40

2520

28

2

050

19

Compog

lass

2

370

21

16

30

22

0

950

10

0

590

050

48

0

050

300

030

240

050

230

03

1

040

160

350

070

290

04

0210

03

0

180

04

Dyract

0

970

06

07

30

05

0

590

06

0

380

040

28

0

040

240

040

190

030

170

02

0

400

040

210

030

190

04

0140

05

0

110

02

Tetric

0

550

08

03

20

04

0

150

03

0

170

220

05

0

01

0

040

0

0

030

0

0

030

0

0

160

050

060

010

040

01

0030

01

0

030

01

Va

luxPlus

0

040

01

00

30

01

0

030

01

0

030

000

03

0

010

030

000

030

010

020

00

0

030

010

030

010

030

01

0020

01

0

030

01

N . A T T A R & A . O N E N794

2002 Blackwell Science Ltd, Journal of Oral Rehabilitation 29; 791798

7/28/2019 1.Attar, 2002

5/9

fluoride-containing glasses and a polyacid liquid

(Smith, 1990). This results in the large surge of ion

release in the first few days as the material sets and the

majority of glass species react. In agreement with

previous studies this experiment showed that the

greatest fluoride release occurred during the first

24 h, diminishing to a significantly lower level the

next day. This result is in accordance with the other

studies reported by El Mallakh and Sarkar (1990), and

also De Schepper et al. (1991). The high concentration

observed in the first days are called the burst effect of

the fluoride. The reason for the rapid fall in fluoride

release is likely to be the result of the initial burst of

fluoride released from the glass particles as they dissolve

in the polyalkenoate acid during the setting reaction.

The later slow release occurs as the glass dissolves in the

acidified water of the hydrogel matrix (De Moor,

Verbeeck & De Maeyer, 1996). The mean fluoriderelease of five aesthetic restorative materials shown as

an example in Fig. 1a, b, reveals the initial burst effect

of Ceramfil b and the release remaining at a certain

constant level for 60 days. However, polyacid-modified

resin composites (compomers) and fluoride-releasing

composite resin did not show an initial fluoride burst

effect.

In the present study, Compoglass and Dyract

released significantly less fluoride initially than did

the conventional glassionomer cement (Ceramfil b),

because the first phase of setting is essentially the

same as that occurring when resin composites are

cured. The initially light cured material takes up water

with time, and the carboxylic groups (COOH) of the

acidic monomer can undergo an acid/base reaction

with metal ions of the glass filler. This, in turn, leads

to the formation of carboxylate salts and the release of

fluoride (Dentsply De Trey, 1996). It seems that this

reaction is weak and results in low fluoride release.

This material behaves more likely as a resin composite

than like glassionomer cement in terms of fluoride

release (Suljak & Hatibovic-Kofman, 1996; Yip &

Smales, 1999). In this study, Compoglass and Dyractin fact seem to follow a similar pattern to Ceramfil b

in having the highest release in the first day and

having progressively less fluoride release as time

progresses.

The second part of the experiment also showed that

all fluoride containing materials released, increased the

amounts of fluoride on exposure to fluoride followed by

a rapid return to near pre-exposure levels alreadyTable

3.

Themeanva

luesof

consequentdifferencesamonggroupsan

dtheresu

ltso

fsignificancetest

Differences

GroupsDay2

Day1Day3D

ay2Day4

Day3Day5

Day4Day15Day5Day30

Day15Day60

Day30Day

1

Day60Day2

Day1Day3

Day2Day4

Day3Day5

Day4

A

13

142

33

3

49

2

54

4

041

18

0

890

96

1

090

90

2

350

76

0

720

82

9031

34

6

611

21

0

890

76

081

0

34

0

470

30

B

0

740

32

0

69

0

25

0

350

10

0

110

08

0

180

06

0

060

06

0

000

04

0800

16

0

680

17

0

070

06

008

0

03

0

030

06

C

0

240

09

0

14

0

07

0

210

07

0

100

06

0

050

05

0

050

05

0

030

04

0240

04

0

190

05

0

020

04

005

0

07

0

030

05

D

0

240

09

0

16

0

05

0

020

22

0

120

22

0

010

01

0

010

01

0

000

01

0130

22

0

100

23

0

030

01

001

0

01

0

000

01

E

0

010

01

0

00

0

01

0

000

01

0

000

01

0

000

01

0

000

01

0

010

01

0010

01

0

000

02

0

000

01

001

0

01

0

010

01

A

B

*

*

*

*

*

*

*

*

*

*

*

*

A

C

*

*

*

*

*

*

*

*

*

*

*

*

A

D

*

*

*

*

*

*

*

*

*

*

*

*

A

E

*

*

*

*

*

*

*

*

*

*

*

*

B

C

B

D

*

*

B

E

*

*

C

D

C

E

D

E

*P