Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 9  |  Issue : 2  |  Page : 91-94

Can exposure to acidic beverages following the application of fluoride varnish cause changes in the amount of fluoride release? an in vitro study


1 Department of Paedodontics & Preventive Dentistry, Kasturba Medical College, Mangalore Manipal University, Mangalore, Karnataka, India
2 Department of Biochemistry, Kasturba Medical College, Mangalore Manipal University, Mangalore, Karnataka, India
3 Department of Public Health Dentistry, Manipal College of Dental Sciences, Mangalore, Kasturba Medical College, Manipal University, Mangalore, Karnataka, India

Date of Web Publication8-Jan-2018

Correspondence Address:
Dr. Arathi Rao
Department of Paedodontics & Preventive Dentistry, Manipal College of Dental Sciences, Mangalore, Kasturba Medical College, Manipal University, Mangaluru, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jofs.jofs_33_17

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  Abstract 


Introduction: Fluoride varnishes are found to be effective in the prevention of early childhood caries. Postvarnish application, the instructions provided by the manufacturer seem to be inadequate because they do not mention the type of beverages which can be consumed after the specified time, considering the widespread consumption of soft acidic drinks in children. Aim: The study was conducted to evaluate the amount of fluoride released from fluoride varnishes − Fluorprotector and Bifluorid in artificial saliva and acidic conditions. Materials and Methods: Polymethyl methacrylate blocks were painted with fluoride varnish and placed into artificial saliva for 30 min. Blocks were then placed in either 1% citric acid or 0.3% citric acid solutions for 30 min with the solutions being replaced every 5 min. The solution was analyzed for fluoride content. Results and Conclusion: The statistical tests applied were repeated measures of analysis of variance and student’s t-test. The level of significance was kept at P < 0.05. Significant difference in fluoride release was noted in different acidic mediums. Fluoride release from fluoride varnishes varied considerably and also depended on the dissolution medium.

Keywords: Acidic condition, fluoride release, fluoride varnish


How to cite this article:
Chakraborty B, Rao A, Chandra RK, Shenoy R, Suprabha BS. Can exposure to acidic beverages following the application of fluoride varnish cause changes in the amount of fluoride release? an in vitro study. J Orofac Sci 2017;9:91-4

How to cite this URL:
Chakraborty B, Rao A, Chandra RK, Shenoy R, Suprabha BS. Can exposure to acidic beverages following the application of fluoride varnish cause changes in the amount of fluoride release? an in vitro study. J Orofac Sci [serial online] 2017 [cited 2019 Aug 19];9:91-4. Available from: http://www.jofs.in/text.asp?2017/9/2/91/222388




  Introduction Top


Fluoride varnishes are recommended by American Dental Association (ADA), Centres for Disease Control and Prevention (CDC), and American Association of Pediatric Dentistry (AAPD)[1],[2],[3] for patients at high risk for dental caries and is said to reduce caries by 25–45%.[4],[5] Postoperative instructions recommend that children do not eat or drink for 30 min after fluoride varnish application so as to maximize the amount of fluoride release.[6] But is there any possibility that the beverage with varying pH consumed immediately after the specified time, influence the fluoride release? None of the manufacturer provides instructions about the type of beverages that can be consumed immediately after the specified time, considering that most of them have acidic pH and also are widely consumed by children. Hence, the aim of the present study was to determine the fluoride release from fluoride varnish in the solution of varying pH.


  Materials and Methods Top


The present study is an in-vitro study. The ethical clearance was obtained from the Institutional Ethics Committee (Letter ref: MCODS/16054 dated 11th June 2016 issued by Institutional Ethics Committee, Manipal College of Dental Sciences, Mangalore) and was conducted at the Department of Biochemistry, Kasturba Medical College, Mangalore and Department of Civil Engineering, National Institute of Technology, Karnataka, Surathkal.

Fluorprotector (Ivoclar Vivadent, India) and Bifluorid 12 (Voco, Germany) were used for the study. Polymethyl methacrylate blocks (1 × 1 sq. in., n = 12) were used as the substrates. Six polymethyl methacrylate blocks were painted with fluoride varnish for each group. Approximately 20 mg varnish was applied on the substrate using the applicator tip provided by the manufacturer. Right after the varnish had dried, the blocks were placed into 60 ml plastic containers. Thirty milliliters of artificial saliva was poured into it, immersing the blocks completely. The containers were then placed onto an orbital shaker set at 100 rpm for 30 min. After 30 min, the decantation of the artificial saliva was performed into a separate container. Then, three of the six blocks per fluoride varnish were subjected to a mild acidic solution (0.3% w/v anhydrous citric acid in deionized water, pH 3.75, adjusted using NaOH), whereas the remaining three blocks were subjected to a strong acidic solution (1% w/v anhydrous citric acid in deionized water, pH 2.27, unadjusted). Thirty milliliters of acidic solutions was poured into each container, immersing the blocks completely. Again the containers were placed onto an orbital shaker set at 100 rpm for 30 min. The decantation of the solutions was performed every 5 min in a separate container. The renewal of the solutions was performed every 5 min for 30 min. Therefore, for each varnish, six samples comprising aliquots of decanted artificial saliva, 18 samples comprising decanted mild acidic solutions, and 18 samples comprising decanted strong acidic solutions were obtained. Fluoride ion sensitive electrode was used for fluoride estimation. The instrument was calibrated using a series of fluoride standards equivalent to 0.5, 1.0, 2.0 mg F−1/L, and standard curves were prepared according to the protocol given by the American Waterworks Association.[7] The preparation procedures have been mentioned below. The aliquots of the decanted artificial saliva and mild and strong acidic solutions were mixed in 1:1 ratio with Total Ionic Strength Adjustment Buffer (II) (TISAB II) fluoride buffer and analyzed for fluoride in comparison to the prepared standard curves by means of fluoride ion-sensitive electrode.

Preparation of the standard fluoride solution:[7] 221.0 mg anhydrous NaF was dissolved in distilled water and diluted to 1000 ml. One hundred milliliters of the solution hence prepared was diluted to 1000 ml with distilled water.

Preparation of the fluoride standard:[7] A series of standards were prepared by diluting with distilled water. 5.0, 10.0, and 20.0 ml of standard fluoride solution were diluted to 100 ml with distilled water. These standards are equivalent to 0.5, 1.0, and 2.0 mg F−1/L. In 100 ml beakers, 10 ml of the standard was added. An equal volume of buffer (TISAB II) was added.

Statistical analysis

Descriptive statistics for mean fluoride release at every 5 min interval till 30 min, in mild and strong acidic solutions for each varnish were tabulated. Student’s t-test was performed to evaluate the fluoride release in mild and strong acidic solution. Repeated measures of analysis of variance (ANOVA) were performed to test for the equality of mean fluoride release from the two fluoride varnishes in different acidic mediums.


  Results Top


Sample size estimation

The sample size and the design were similar to the study by Lippert.[8] Twelve polymethyl methacrylate blocks were used, six for each varnish, exposing each of them to artificial saliva after which three blocks were exposed to mild acidic solutions and the other three blocks were exposed to strong acidic solutions. Renewal of the solutions was performed every 5 min till 30 min. Therefore, for each varnish, six samples comprising aliquots of decanted artificial saliva, 18 samples comprising decanted mild acidic solutions, and 18 samples comprising decanted strong acidic solutions were obtained. Thus, a total of 42 samples were tested for fluoride release for each fluoride varnish.

Both Fluorprotector and Bifluorid 12 showed a similar, gradual decrease in fluoride release with continuing acid exposure as shown in [Figure 1].
Figure 1: Fluoride release from Fluorprotector and Bifluorid varnish – into artificial saliva (0–30 min), followed by erosive solutions (30–60 min) in 5 min intervals. FPV = Fluorprotector varnish, BFV = Bifluorid varnish, and CA = citric acid

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The mean fluoride release in different acidic mediums is shown in [Table 1]. Fluoride release was more in the 1% citric acid group when compared to 0.3% citric acid group, and the difference was statistically significant (P < 0.05) as seen in [Table 2] and [Table 3]. Fluoride release from both the varnish groups was more in 1% citric acid group. Intragroup comparison shows that the fluoride release in Fluorprotector was less compared to Bifluorid 12, but for both, statistically significant values (P < 0.05) were obtained as seen in [Table 2] and [Table 3]. Repeated measures of ANOVA revealed statistically significant difference at 5 min (P = 0.018), 15 min (P = 0.028), and 25 min (P = 0.014). The lowest value for fluoride release was for Fluorprotector varnish at 0.3% citric acid at 25 min (P < 0.05). The highest value was for Bifluorid varnish at 1% citric acid at 5 min (P < 0.05).
Table 1: Mean fluoride release (μg fluoride/g fluoride varnish) ± standard deviation

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Table 2: Results of the independent t-test performed for intragroup comparison of fluoride release from Fluorprotector varnish in two different acidic mediums

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Table 3: Results of the independent t-test performed for intragroup comparison of fluoride release from Bifluorid varnish in two different acidic mediums

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  Discussion Top


The present experiment was intended to mimic the clinical situation following a fluoride varnish application − with the child being refrained to drink anything for 30 min following fluoride application. This is followed by exposure to a drink with low pH over an equal period of time. The design of the study was similar to a study by Lippert.[8]

Most of the soft drinks available in the market are in the pH range of 2–3. Reddy et al.[9] found that 39% of the beverages were found to be extremely erosive (pH < 3.0) and 54% to be erosive (pH 3.0–3.99). This is the reason we chose 0.3 and 1% citric acid (pH of 3.3 and 2.2, respectively) in the present study.[10] Fluorprotector and Bifluorid 12 were chosen for the study because they were routinely preferred and used in our department.

Justification for the use of polymethyl methacrylate blocks

The study aimed at testing whether fluoride release would be different between the two commonly used fluoride varnishes using a simple model, without interference of their reaction with tooth and if a difference existed, could it be explained by differences in the fluoride release pattern.

Few studies present in the literature have used polymethacrylate blocks/acrylic blocks/plastic substrates as their study substrates to check for fluoride release from varnishes.[8],[11],[12]

Studies show that the duration of contact of the fluoride agent with the enamel strongly influences the uptake of fluoride, its reaction, and release in the enamel.[11] The expected outcome of the fluoride varnish is the slow and steady release of fluoride over an extended period of time. On the basis of the present study, acidic solutions have the potential to “leach out” fluoride from the fluoride varnish. Fluoride applied at high concentrations, such as from fluoride varnish, gels, and foams, primarily forms non-stoichiometric calcium fluoride, which is very labile and soluble at low pH.[13] Therefore, it is very important that children avoid consumption of drinks with very low pH even after the mentioned 30 min. But none of the manufacturer’s instructions mentions this point.

Fluorprotector showed much less fluoride elevation in artificial saliva and also in different acidic mediums when compared to Bifluorid 12. Following application of fluoride varnish, calcium fluoride globules form on the tooth surface, which act as an insoluble reservoir and as the solvents evaporate, the fluoride concentration at the tooth surface increases to considerably higher value (nearly four times higher).[14] For this to happen, fluoride has to be released from the varnish in a slow and steady way to have impact on the prevention of caries rather than sudden increased release as observed in the present study under acidic environment.[11]

Clinical implication

Children are quite fond of acidic soft drinks. The consumption of acidic soft drinks is a major contributing etiological factor in dental erosion.[15] The study findings depict that the consumption of such drinks causes immediate and fast leach out of the fluoride from the fluoride varnish instead of slow and steady release. This will reduce the concentration of fluoride finally available and thus decrease the benefit of the topically applied fluoride varnish. Thus, post-treatment instructions following application of fluoride varnish should be modified and the consumption of acidic soft drinks should be avoided.

Acknowledgements

We would like to thank Mr. Manohar SK, Senior Technical Assistant, Department of Civil Engineering, NITK Surathkal.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Centers for Disease Control and Prevention. Recommendations and reports: Recommendations for using fluoride to prevent and control dental caries in the United States. MMWR 2001;50:1-42. Available from: https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm. [Last assessed on 2016 Dec 14].  Back to cited text no. 1
    
2.
American Dental Association Council on Scientific Affairs. Professionally applied topical fluoride: Evidence-based clinical recommendations. J Am Dent Assoc 2006;137:1151-9.  Back to cited text no. 2
[PUBMED]    
3.
Guideline on fluoride therapy. Pediatr Dent 2014;37:176-9.  Back to cited text no. 3
    
4.
Autio-Gold JT, Courts F. Assessing the effect of fluoride varnish on early enamel carious lesions in the primary dentition. J Am Dent Assoc 2001;132:1247-53.  Back to cited text no. 4
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5.
Weintraub JA, Ramoz-Gamoz F, Jue B, Shain S, Hoover CI, Featherstone JD et al. Fluoride varnish efficacy in preventing early childhood caries. J Dent Res 2006;85:172-6.  Back to cited text no. 5
    
6.
Fluoride Varnish Application − NHS Scotland. Available from: http://www.child-smile.org.uk/professionals/fluoridevarnish1app.aspx. [Last assessed on 2016 Dec 14].  Back to cited text no. 6
    
7.
Rice EW, Baird RB, Eaton AD, Clesceri LS. Standard Methods for the Examination of Water and Wastewater. 22nd ed. United States: American Public Health Association, American Waterworks Association, Water Environment Federation; 2012.  Back to cited text no. 7
    
8.
Lippert F. Fluoride release from fluoride varnishes under acidic conditions. J Clin Pediatr Dent 2014;39:35-9.  Back to cited text no. 8
[PUBMED]    
9.
Reddy A, Norris DF, Momeni SS, Waldo B, Ruby JD. The pH of beverages in the United States. J Am Dent Assoc 2016;147:255-63. http://www.endmemo.com/chem/phcal.php. [Last assessed on 2016 Dec 14].  Back to cited text no. 9
    
10.
http://www.endmemo.com/chem/phcal.php. [Last assessed on 2016 Dec 14].  Back to cited text no. 10
    
11.
Shen C, Autio GJ. Assessing fluoride concentration uniformity and fluoride release from three varnishes. J Am Dent Assoc 2002;133:176-82.  Back to cited text no. 11
    
12.
Comar LP, Souza BM, Grizzo LT, Buzalaf MA, Magalhães AC. Evaluation of fluoride release from experimental TiF4 and NaF varnishes in vitro. J Appl Oral Sci 2014;22:138-43.  Back to cited text no. 12
    
13.
Okunseri C, Okunseri E, Gonzalez C, Visotcky A, Szabo A. Erosive tooth wear and consumption of beverages among children in the United States. Caries Res 2011;45:130-5.  Back to cited text no. 13
    
14.
Subramaniam P, Sangeeta T. Effect of different concentrations of fluoride varnish on enamel surface microhardness: An in vitro randomized controlled study. J Ind Assoc Public Health Dent 2016;4:344-7.  Back to cited text no. 14
    
15.
Jablonowski BL, Bartoloni JA, Hensley DM, Vandewalle KS. Fluoride release from newly marketed fluoride varnishes. Quintessence Int 2012;43:221-8.  Back to cited text no. 15
    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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