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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 2  |  Issue : 2  |  Page : 69-73

Fluoride release and recharge abilities of zinc-reinforced glass ionomer cement in comparison to traditional high strength glass ionomers


1 Departmen of Pediatric Dentistry, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia
2 Departmen of Pediatric Dentistry, Dean of Postgraduate Studies and Research, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia
3 Preventive Dental Sciences, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia

Date of Web Publication14-Jul-2015

Correspondence Address:
Adel Ahmed Bamoussa
Department of Pediatric Dentistry, Riyadh Colleges of Dentistry and Pharmacy, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1658-6816.160763

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  Abstract 

Aim: The aim of this study was to compare the fluoride release and recharge characteristics of a zinc reinforced glass ionomer cement (GIC) (ChemFil Rock ™, Dentsply, York PA, USA) to that of two traditional high strength GICs (Fuji IX ™, GC Corp, Japan and Ketac-Fil™, 3M-ESPE, Germany).
Materials and Methods: A total of 60 specimens (20 in each group) were used in this study. The materials were prepared according to the manufacturers' instructions and placed in plastic molds 9 mm in diameter and 2 mm high. The 20 specimens in each group were further subdivided into two subgroups of 10 each. Subgroup A (control) involved no fluoride treatment. Subgroup B involved application of a 1450 ppm dentifrice for 2 min twice daily for 30 days with a soft toothbrush. The specimens were then suspended in airtight plastic bottles containing 20 ml deionized water. A fluoride electrode was used to measure fluoride release and recharge from the discs on the 1 st , 2 nd , 7 th , 15 th , and 30 th day.
Results: The results of the study showed that the zinc reinforced glass ionomer had a significantly higher fluoride release and recharge when compared to conventional high strength glass ionomers.
Conclusions: The results of this study suggest that zinc reinforced glass ionomers have better fluoride recharge and release characteristics than conventional high strength glass ionomer.

Keywords: Fluoride, fluoride recharge, glass ionomer cement


How to cite this article:
Bamoussa AA, Assery MK, Pani SC. Fluoride release and recharge abilities of zinc-reinforced glass ionomer cement in comparison to traditional high strength glass ionomers. Saudi J Oral Sci 2015;2:69-73

How to cite this URL:
Bamoussa AA, Assery MK, Pani SC. Fluoride release and recharge abilities of zinc-reinforced glass ionomer cement in comparison to traditional high strength glass ionomers. Saudi J Oral Sci [serial online] 2015 [cited 2019 Jun 20];2:69-73. Available from: http://www.saudijos.org/text.asp?2015/2/2/69/160763


  Introduction Top


One of the most desirable properties of restorative material is that it should have caries-inhibiting properties. [1] Fluoride plays an important role in caries prevention, and efforts have been made to incorporate fluoride into different preventive materials. [2],[3] Glass ionomer cements (GICs) were originally developed as a more biocompatible alternative to silicate cements. [4] Fluoride is used as a flux to reduce the fusion temperature of the glass during manufacture, this gives the cements a natural property of fluoride release. [1],[4] Research studying the pattern of release of fluoride from restorative materials in the 1990's showed that when GICs are exposed to a source of fluoride, they imbibe fluoride ions, thus acting as a "fluoride reservoir." [1],[5],[6] Fluoridated dentifrices are the most common source of fluoride used on a daily basis, and it is for this reason that fluoridated toothpastes have been used to measure fluoride release and recharge. [7],[8] The concentration of fluoridated pastes may vary from 500 ppm for children's pastes to as high as 5,000 ppm in high fluoride toothpastes. [9]

Despite having acceptable esthetics, one of the drawbacks of GIC, when used as a restorative material is its relatively poor strength. [8],[10],[11] To address this concern several "high strength" GICs have been developed by either reinforcing them with materials such as resins, metals, or modifications to the glass. [11] However, it has been repeatedly shown that the fluoride release of a GIC is inversely proportional to its mechanical properties. [11] Recently, a GIC has been developed using zinc to enhance mechanical properties instead of traditional resin or metal additives (ChemFil Rock ™, Dentsply, York PA, USA). This material has been shown to have the better flexural tensile strength and lower though comparable compressive strength when compared to traditional high strength GICs. [12] However, little is known about the fluoride release and recharge characteristics of this cement when exposed to a fluoridated dentifrice.

Given this paucity in data the aim of this study was to compare the fluoride release and recharge characteristics of a zinc reinforced GIC (ChemFil Rock ™, Dentsply) to that of two conventional high strength GICs (Fuji IX ™, GC Corp, Japan and Ketac-Fil™, 3M-ESPE, Germany).


  Materials and Methods Top


Ethical clearance for the study was obtained from the research center of Riyadh Colleges of Dentistry and Pharmacy, and the proposal was assigned the registration number PGRP/43235003/7.

Study design

The study followed an experimental design using a fluoride electrode to measure the fluoride release and recharge characteristics of the three cements.

Sample power calculation

Sample power was calculated using G-power 3.1 sample power calculator (Universtat Kiel, Germany). A sample size of 20 in each group was required to obtain a (1-β) of 0.95 and α of 0.05 in order for the sample to have adequate power (Buchner et al., 1997).

Preparation of the sample

A total of 60 discs (20 in each group) were used in this study. Group 1 comprised of discs made up of zinc reinforced glass ionomer (Chemfil Rock, Dentsply, USA) while groups 2 (Fuji IX, Fuji Corp. Japan) and 3 (Ketac Fil, 3M-ESPE, Germany) comprised of discs made up of conventional high strength glass ionomer. The materials were prepared according to the manufacturers' instructions and were placed in plastic molds 9 mm in diameter and 2 mm high.

Excess materials were removed and a dental floss (for suspension in solution) was imbedded into each specimen.

The 20 specimens in each group were further subdivided into two subgroups of ten each. Subgroup A comprised of 10 specimens that were not subjected to fluoride recharge. Subgroup B comprised of 10 specimens that were subjected to a twice daily application of a 1450 ppm dentifrice (Crest, Germany) for 2 min every 12 h for 30 days with an electronic vibrator soft toothbrush (Trisa, Switzerland). The amount of toothpaste was determined by using a graduated syringe. 0.5 CC of toothpaste was used for each sample.

After fluoride treatment, each specimen was wiped clean with a tissue and then was rinsed by exposing each side to a stream of double distilled water for 20 s. Each specimen was dried for 2 min on an absorbent paper. The specimens were then suspended in airtight plastic bottles containing 20 ml deionized water.

Measurement of fluoride release and recharge

Fluoride concentration measurement of each specimen was performed after rinsing each specimen with 1 mL of deionized water in the plastic container and transferring them to a new plastic container with 4 mL of deionized water. 0.5 mL of total ionic strength adjustment buffer (TISAB III, Thermo Fisher Scientific, Beverly, MA, USA) was added at 10 volume percentage to provide constant ionic strength for fluoride measurement. The samples were the fluoride concentration of the water in which the specimens were immersed, was measured by means of a fluoride ion selective electrode, (781 pH/ion meter, Metrohm, Switzerland) that was connected to an ion selective electrode meter/digital ion analyzer. Based on protocols used in earlier studies, it was decided to record fluoride measurements at intervals of 1, 2, 7, 15, and 30 days. [8],[10]

Statistical analyses

The one-way ANOVA and Scheffe's post-hoc test were used to determine the significance of the difference in fluoride release between the different cement used. The student's t-test was used to measure the significance difference between the groups.


  Results Top


Fluoride release

The fluoride release of the cements (without recharge) was tabulated using the results from the control group. It was seen that all groups had a sharp drop in fluoride release over the 1 st 2 weeks. The significance of the difference between these groups was however only seen in the 1 st 2 weeks. After 1-week, there were no significant differences between the groups [Chart 1 [Additional file 1]] and [Table 1].
Table 1: Mean fluoride release from each of the cements in the control group (without recharge)

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When tested using the one-way ANOVA and the Scheffe's post-hoc test, it was found that the zinc reinforced cement had significantly higher fluoride release than both the conventional high strength cements on all days. Among the conventional high strength cements Ketac-fil (3M ESPE) had significantly higher release than Fuji IX (Fuji Corp.) on day 2 and day 30 [Table 2].
Table 2: Scheff e's post-hoc test showing the level of significance between groups without fluoride recharge

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Fluoride release

The fluoride release and recharge were measured in samples recharged with fluoridated toothpaste (test group). It was seen that all groups had a drop in fluoride release over the first 2 days, the level of the drop, however, tapered after 1-week. The zinc reinforced GIC showed a significantly higher release of fluoride at each time interval indicating that the zinc reinforced glass ionomer had a greater ability for release and recharge of fluoride [Chart 2 [Additional file 2]] and [Table 3].

When tested using the one-way ANOVA and the Scheffe's post-hoc test, it was found that the zinc reinforced cement had significantly higher release and release than both the conventional high strength cements on all days [Table 4]. Furthermore, it was observed that while the Ketac-fil had significantly higher release and release of fluoride than Fuji IX on day 1 and day 2, both high strength cements had similar release and release characteristics after the 1 st week [Table 2].
Table 3: Mean fluoride release from each of the cements after recharge with a 1450 ppm toothpaste

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Table 4: Scheff e's post-hoc test showing the level of significance between groups after fluoride recharge using a 1450 ppm fluoridated toothpaste

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  Discussion Top


The role of GIC, a reservoir of fluoride, has been long recognized, with several early studies showing that glass ionomers had both release and recharge characteristics. [13],[14],[15] Later research showed that the release characteristics of glass ionomers were inversely proportional to the amount of fillers added. [11] The change in fluoride release and release characteristics of glass ionomers have been extensively evaluated with respect to the addition of resin, such as with compomers, resin modified glass ionomers and resin reinforced and other high strength glass ionomers. [5],[16],[17],[18],[19] The goal of this study was to assess if the addition of zinc changed the fluoride release and recharge behavior of glass ionomer when compared to the more traditional high strength cements.

Early studies established that the release of fluoride from GICs follows an exponential rather than linear pattern with the release being maximum in the first two 2 days after the restoration is placed in the oral cavity reducing to clinically insignificant amounts (<1 ppm) by the 30 th day. [17],[19],[20],[21] It is for this reason that the in vitro model used in this study measured fluoride at the 1 st , 2 nd , 7 th , 15 th , and 30 th day rather than measurements taken on each day. This is in keeping with the models used by more recent studies on fluoride release and release from restorative materials. [8],[10]

This study is one of the first to evaluate the fluoride release and release characteristics of GIC reinforced with zinc. It was observed that in the absence of a recharge with a fluoridated toothpaste, the zinc reinforced GIC had significantly greater release of fluoride than the high strength GICs studied (Fuji IX, Fuji Corp.; Ketac fil, 3M-ESPE) a fact that was replicated when the samples were recharged with a 1,450 ppm fluoridated dentifrice.

The relationship between mechanical properties and fluoride release of glass ionomers has been previously studied not only in GICs reinforced with resins, but also in GICs reinforced with titanium fluoride, [22] nanocomposites [23] and calcium hydroxyapatite. [24] In all cases, it has been shown that the addition of fillers results in a fluoride release that is either comparable to or less than that of high strength glass ionomers. It is interesting that the addition of zinc offers increased fluoride release and release. The exact mechanism of this release is not clearly understood and further research is needed to evaluate if this property is related to the physical nature of zinc, or the chemical interaction between zinc and the glass ionomer matrix.


  Conclusion Top


Based on the findings of this study, it can be concluded that the zinc reinforced GIC has significantly higher fluoride release as well as recharge properties when compared to traditional high strength GICs. However, given the paucity of literature and the novelty of the cement, further research is needed to explore the clinical implications of this finding.

Financial support and sponsorship

Nil.

Conflict of interest

There are no conflicts of interest.

 
  References Top

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Rothwell M, Anstice HM, Pearson GJ. The uptake and release of fluoride by ion-leaching cements after exposure to toothpaste. J Dent 1998;26:591-7.  Back to cited text no. 1
    
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Gatti A, Camargo LB, Imparato JC, Mendes FM, Raggio DP. Combination effect of fluoride dentifrices and varnish on deciduous enamel demineralization. Braz Oral Res 2011;25:433-8.  Back to cited text no. 9
    
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23.
Rajabzadeh G, Salehi S, Nemati A, Tavakoli R, Solati Hashjin M. Enhancing glass ionomer cement features by using the HA/YSZ nanocomposite: A feed forward neural network modelling. J Mech Behav Biomed Mater 2014;29:317-27.  Back to cited text no. 23
    
24.
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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