Eur Arch Paediatr Dent DOI 10.1007/s40368-014-0122-3
ORIGINAL SCIENTIFIC ARTICLE
An in vitro assessment of fluoride uptake by tooth enamel from four different fluoride dentifrices V. H. Patil • R. T. Anegundi
Received: 4 January 2014 / Accepted: 11 February 2014 Ó European Academy of Paediatric Dentistry 2014
Abstract Aim The aim of this study was to evaluate fluoride uptake by tooth enamel with four different fluoride dentifrices. Study design Sixty human premolars extracted for orthodontic purpose were selected for the study. The teeth were covered with nail varnish leaving a window of 4 9 4 mm on the enamel surface of the buccal and lingual sides. The teeth were demineralised and were divided into four groups with 15 teeth in each group. The buccal window served as experimental and the lingual as control. The teeth were immersed in toothpaste slurry containing: sodium fluoride (Group A); sodium monofluorophosphate (Group B); stannous fluoride (Group C) and amine fluoride (Group D). The fluoride content in the etched superficial enamel layer in the windows was analysed using a fluoride ion-specific electrode. Results Within the parameters of this study, the uptake of fluoride was statistically significant in Group D (p \ 0.05). The uptake of fluoride by tooth enamel in an increasing order was Group A \ Group B \ Group C \ Group D. Conclusion The study showed that enamel treated with amine fluoride had the highest fluoride uptake. Keywords enamel
Fluoride dentifrice Remineralisation Tooth
Work attributed to Department of Pedodontics and Preventive Dentistry, SDM College of Dental Sciences and Hospital, Dharwad India. V. H. Patil (&) R. T. Anegundi Department of Pedodontics and Preventive Dentistry, KLE VK Institute of Dental Sciences, Nehru Nagar, Belgaum, Karnataka 590010, India e-mail: [email protected]
Introduction More than a century ago, research was started on the effect of fluoride on oral health. It was in the second half of the 20th century that the focus of the research was upon the development and evaluation of different fluoride formulations. The fluoride which is incorporated into the crystalline lattice of the dental hard tissues making it less soluble in acid environment has been the scientific basis for the prevention of dental caries. Continuous research confirm that topical fluoride application is more effective in caries prevention than systemic fluoride application. In vitro studies showed that topical fluoride application produced 20 times higher fluoride levels in the superficial layer of enamel and dentine than the initial fluoride content in deeper layers. A 20–40 % cariespreventive effect of topical fluoride agents was shown in clinical studies (Ripa 1990; ten Cate 1999; Clarkson 2000; Holler et al. 2002; Petersen and Lennon 2004). Among caries-preventive protocols, fluoride-containing dentifrices are well accepted (Arnold et al. 2006). Dentifrices have been widely adopted as the principle means of delivering topical fluoride around the world for caries-preventive benefits (Zero 2006). The bioavailability of fluoride is very important for the caries-preventive effect which in turn is dependent on the solubility of fluoride-containing compounds leading to the adhesion of that fluoride compound to the tooth surface. From in vitro studies, it is well known that inorganic and organic fluorides in tooth-paste systems cause markedly different uptake of fluoride on tooth enamel and have different influences on remineralisation (Arnold et al. 2006). Hence, the aim of this study was to evaluate and investigate the possible differences in fluoride uptake on tooth enamel from four different fluoride formulations in commercially available dentifrices.
123
Eur Arch Paediatr Dent
Fig. 1 Window measuring 4 9 4 mm
Fig. 2 Demineralised window
Materials and methodology
displayed demineralisation clinically as white chalky spots (Fig. 2). The lingual window was covered with an acid resistant nail varnish of different colour. The teeth were then immersed in different dentifrice slurries and incubated at 37 ° C for 2 days which simulates 2 years of tooth brushing twice daily for 2 min per day (Arnold et al. 2006). The pH of the slurries was evaluated prior to the immersion of the sample teeth. The pH was: 8.15, 9.43, 5.34 and 5.05 for groups A, B, C and D, respectively. The teeth were then washed with double de-ionised distilled water and dried. The acid biopsy technique was used for fluoride ion estimation. The samples were etched for 60 s in 10 ml of 0.5 M perchloric acid separately in the experimental window followed by the control window after cleaning the nail varnish from the control window with acetone. To this, 10 ml of total ionic strength adjustment buffer (TISAB-II) was added. The fluoride concentration in solution was determined with Orion 9609 BNWP fluoride ion-specific electrode (Thermo Scientific, USA) and expressed in mg/L (Table 1). The mean and standard deviation between the experimental and control windows of the various groups were compared using the independent samples t test while pairwise comparison of different groups was undertaken using the one-way ANOVA followed by post-hoc Tukey’s HSD test. The statistical significance was set at a p value of\0.05.
Sixty healthy human premolars extracted for orthodontic purposes were used as study samples. The teeth were cleaned for surface debris, calculus and periodontal tissue attachments by scaling and root planing, followed by pumice prophylaxis. The teeth were stored in double deionised distilled water until use. The teeth were then covered with an acid-resistant nail varnish leaving 4 9 4 mm window on the buccal and lingual surfaces of the crown (Fig. 1). The buccal window in each tooth served as the experimental window and the lingual window as the control. The teeth were then randomly divided into four groups, 15 teeth in each group and a control group within. The groups were: Group A (Colgate Total, ColgatePalmolive company, India) sodium fluoride dentifrice (NaF) 1,000 mg/L of F, Group B (Colgate Strong Teeth, Colgate-Palmolive company, India) sodium monofluorophosphate dentifrice (NaMFP) 1,000 mg/L of F, Group C (Sentium, Dent Aids, India) stannous fluoride dentifrice (SnF2) 1,000 mg/L of F and Group D (Amflor, Group Pharmaceuticals Limited, India) amine fluoride dentifrice (AmF) 1,000 mg/L of F. The teeth were demineralised in 500 ml solution containing 0.1 M lactic acid with 3 mM calcium chloride, 1.8 mM potassium dihydrogen phosphate and 40 % NaOH at a pH of 4.5 for 2 days at 37 °C in an incubator. The solution was changed every 12 h to avoid variation of the pH of the demineralising solution. After demineralisation, the teeth were cleaned thoroughly with double de-ionised distilled water. The windows
123
Results The uptake of fluoride by tooth enamel in the experimental windows of groups A, B, C and D with their respective
Eur Arch Paediatr Dent
control windows were statistically very highly significant (Table 1; Fig. 3). The p value of group A with respect to groups B, C and D was very highly significant. The p value of group B with groups C and D was also very highly significant. Whereas the p value of group C with group D was highly significant (Table 2). The results showed that the uptake of fluoride by tooth enamel was highest in samples treated with AmF toothpaste slurry when compared to the samples treated with SnF2, NaMFP and NaF toothpaste slurries.
Discussion The benefits of at-home topical fluorides in a wide variety of formulations such as mouth rinses, dentifrices, gels and solutions are universally encouraged by dental professionals and accepted by the community. Fluoride dentifrices have been proven effective anti-caries agents since 1955. Bibby put forward the idea that frequent application of fluoride from a dentifrice might provide an effective
Table 1 Comparison of experimental and control windows with fluoride uptake in different groups Groups Group A
Window
Meana
Experiment
10.3135
2.1721
7.4629
1.0753
14.1762
1.4140
Control Group B
Experiment Control
Group C Group D
SDa
*0.0001
7.7245
0.9950
Experiment
19.4428
1.4299
Control
10.0063
0.9080
*0.0000
Experiment Control
21.6793 9.3173
2.4559 1.4905
*0.0000
* indicates significance (p \ 0.05) a
p value
Fluoride values expressed in mg/L (equivalent to ppm F)
*0.0000
form of caries prophylaxis. Although earlier studies did not attend with success, they probably marked the start of the quest for effective fluoride dentifrice systems (Bibby 1945; Stewart et al. 1982). The observations of this study showed that there was uptake of fluoride by demineralised tooth enamel surfaces in the experimental windows compared to their respective controls. The uptake of fluoride in AmF group was statistically very highly significant when compared to other groups, the uptake of fluoride in SnF2 group was statistically very highly significant when compared to the group containing NaMFP and NaF and the uptake of fluoride in NaMFP group was statistically very highly significant than in the group containing NaF. It can be concluded from the above data that the samples treated with AmF showed the highest fluoride uptake in the tooth enamel followed by the ones treated by SnF2, and NaMFP, with NaF being the least. Similar results were seen in other studies with teeth treated using these dentifrices (Chan et al. 1991; Klimek 1998). The mean uptake of fluoride values was comparatively more in one study (Chan et al. 1991) than those found in the present study and this could be because of the higher strength of the fluoride solutions that were used, whereas the study by Klimek (1998) noticed lower fluoride uptake; this could be because they used an indirect method for fluoride estimation where some of the fluoride remained complexed (Chan et al. 1991; Klimek 1998). Studies on remineralisation of bovine enamel were evaluated after treating with NaF, AmF dentifrices and placebo solution. The results were in favour of AmF for remineralisation (Buchalla et al. 2002; ten Cate et al. 2008). However, one other study noticed no difference in uptake of fluoride between groups treated with AmF and NaF (Toda and Featherstone 2008). The SnF2 group showed a higher uptake of fluoride compared to the ones treated with NaMFP and NaF, and the group treated with NaMFP showed higher uptake of
Fig. 3 Showing the comparison of fluoride uptake in mg/L between experimental and control window among the four groups
123
Eur Arch Paediatr Dent Table 2 Pair-wise comparison of fluoride scores in the experimental windows of the four groups Group
Group A
Group B
Group C
Group A
–
Group B
*0.0002
–
Group C
*0.0002
*0.0002
–
Group D
*0.0002
*0.0002
*0.0124
Group D
–
* indicates significance (p \ 0.05)
fluoride compared to the group treated with NaF. In contrary to this, a previous study noticed a higher F uptake in NaF-based paste compared to NaMFP and SnF pastes (Reintsema et al. 1985). The sample treated with AmF showed the highest fluoride uptake in the tooth enamel followed by the ones treated with NaMFP and NaF. Several other studies have shown the fluoride uptake of demineralised human dental enamel to be significantly higher in groups treated with an AmF toothpaste (Klinger and Wiedemann 1986; To´th et al. 1998; Arnold 2006; Altenberger et al. 2010). However, two of these studies (To´th et al. 1998; Altenberger et al. 2010) noticed fluoride uptake by NaF toothpaste was higher than that found in NaMFP toothpaste, which was in contrast with the present study. This could be because NaF is ionically bonded, which appears to be critical for fluoride uptake, rather than the covalently bonded NaMFP toothpaste. However, in the present study, NaMFP group showed a higher F uptake which is consistent with a previous study (Arnold 2006). In this study, the pH of the toothpastes was evaluated prior to the immersion of the samples. It was noticed after treatment of the samples with their respective slurries that the uptake of fluoride was statistically very highly significant in groups treated with AmF and SnF2 when compared to groups treated with NaMFP and NaF. This can be attributed to the well-known fact that the reaction between enamel and fluoride is faster, and that fluoride uptake on and in enamel is higher at lower pH (Saxegaard and Rølla 1988; van Strijp et al. 1999; Altenberger et al. 2010). The highest uptake of fluoride was seen in the AmF group. AmF is an organic fluoride, whereas the other fluoride dentifrices used in the study are inorganic. The distribution of organic material is increased in demineralised enamel and this explains the higher uptake of organic fluoride. The cations in AmF, as in other surfactants, have a hydrophilic and a hydrophobic part. The electrostatic attraction holds the positively charged nitrogen atom and the negatively charged fluoride ions in close vicinity at the hydrophilic end. With its positive charge it can attach itself easily to the predominantly charged negatively charged
123
enamel surface. Thus, the hydrophobic part is aligned towards the oral cavity and the hydrophilic towards the tooth surface. Hence, the fluoride ions accumulate close to the tooth surface by this self-organised arrangement. Thus, the accumulated fluoride is available directly for the production of calcium fluoride as a labile reservoir or is available immediately for remineralisation. The surface layer of calcium fluoride is stabilised by the hydrophobic part of molecule pointing towards the oral cavity which reduces moistening by saliva and prevents it being washed out rapidly (Schmid 1983). On other hand, the other fluorides used in the present study are inorganic fluorides which are lost by way of ionic exchange in the saliva. Conclusion Dentifrices play an essential role in our daily oral hygiene maintenance. Fluoride deposition into partially demineralised enamel is one of the several important factors in the cariostatic activity of topical fluorides. The amount of fluoride present in the tooth enamel is an important component in caries prevention. This study evaluated the uptake of fluoride by tooth enamel by comparing dentifrices containing different fluoride formulations, i.e. NaF, NaMFP, SnF2 and AmF. It can be concluded that the uptake of fluoride was statistically highly significant with the group treated with AmF than with groups treated with other fluoride formulations. Some of the factors which may have influenced the observations found in this study are: variation in the initial fluoride levels in human teeth since they were collected from many individuals residing in different geographic locations and the fluoride level varies strongly with the location on the tooth surface. However, further detailed in vivo studies with larger sample size may be required for evaluating the uptake of fluoride on tooth enamel with different fluoride formulations in the dentifrice.
References Altenberger MJ, Bernhart J, Schicha TD, Wrbas KT, Hellwig E. Comparison of in vitro fluoride uptake from whitening toothpastes and a conventional toothpaste in demineralised enamel. Schweiz Monatsschr Zahnmed. 2010;120(1):104–8. Arnold WH, Dorrow A, Langenhorst S, et al. Effect of fluoride toothpastes on enamel demineralization. BMC Oral Health (serial online) 2006 June (cited 2006 June);6(8):(6 screens). http://www.biomedcentral.com/1472-6831/6/8. Bibby BG. A test of the effect of fluoride containing dentifrices on dental caries. J Dent Res. 1945;24:297–303. Buchalla W, Attin T, Schulte-Mo¨nting J, Hellwig E. Fluoride uptake, retention, and remineralization efficacy of a highly concentrated fluoride solution on enamel lesions in situ. J Dent Res. 2002;81(5):329–33.
Eur Arch Paediatr Dent ten Cate JM. Current concepts on the theories of the mechanism of action of fluoride. Acta Odontol Scand. 1999;57:325–9. ten Cate TM, Buijs MJ, Miller CC, Exterkate RAM. Elevated fluoride products enhance remineralization of advanced enamel lesions. J Dent Res. 2008;87(10):943–7. Chan JCY, Hill FJ, Newman HN. Uptake of fluoride by sound and artificially carious enamel in vitro following application of topical sodium and amine fluorides. J Dent. 1991;19(2):110–5. Clarkson JJ. International collaborative research on fluoride. J Dent Res. 2000;79:893–904. Holler BE, Friedl KH, Jung H, Hiller KA, Schmalz G. Fluoride uptake and distribution in enamel and dentin after application of different fluoride solutions. Clin Oral Invest. 2002;6:137–44. Klimek J. Fluoride uptake in dental enamel following the use of NaF and amine fluoride toothpastes—an in situ study. Oralprophylaxe. 1998;20(4):192–6. Klinger HG, Wiedemann W. Enhancement of in vivo remineralization of approximal initial caries in man by an organic and inorganic remineralization agent. Arch Oral Biol. 1986;31:269–72. Petersen PE, Lennon MA. Effective use of fluorides for the prevention on dental caries in the 21st century: the WHO approach. Community Dent Oral Epidemiol. 2004;32:319–21. Reintsema H, Schuthof J, Arends J. An in vivo investigation of the fluoride uptake in partially demineralised human enamel from several different dentifrices. J Dent Res. 1985;64(1):19–23.
Ripa LW. An evaluation of the use of professional (operator-applied) topical fluorides. J Dent Res. 1990;69:786–96. Saxegaard E, Rølla G. Fluoride acquisition on and in human enamel during topical application in-vitro. Scand J Dent Res. 1988;96:523–35. Schmid H. Chemie und Oberfla¨chenwirkung der aminfluoride. Dtsch Zahna¨rzth Z. 1983;1:9–13. Stewart RE, Barber TK, Troutman KC, Wei SHY. Pediatric dentistry—Scientific foundations and clinical practice. St Louis(MI): Mosby; 1982. van Strijp AJP, Buijs MJ, ten Cate JM. In situ fluoride retention in enamel and dentin after the use of an amine fluoride dentifrice and amine fluoride/sodium fluoride mouthrinse. Caries Res. 1999;33:61–5. Toda S, Featherstone JD. Effects of fluoride dentifrices on enamel lesion formation. J Dent Res. 2008;87(3):224–7. To´th Z, Gintner Z, Banoczy J. Effect of different fluoride-containing toothpastes on human dental enamel in vitro. Caries Res. 1998;32:275–6. Zero DT. Dentifrices, mouthwashes, and remineralization/caries arrestment strategies. BMC Oral Health. (serial online) 2006 July (cited 2006 July); 6(S9):(13 screens). http://www.biomed central.com/1472-6831-6-S1-S9.
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ORIGINAL SCIENTIFIC ARTICLE
An in vitro assessment of fluoride uptake by tooth enamel from four different fluoride dentifrices V. H. Patil • R. T. Anegundi
Received: 4 January 2014 / Accepted: 11 February 2014 Ó European Academy of Paediatric Dentistry 2014
Abstract Aim The aim of this study was to evaluate fluoride uptake by tooth enamel with four different fluoride dentifrices. Study design Sixty human premolars extracted for orthodontic purpose were selected for the study. The teeth were covered with nail varnish leaving a window of 4 9 4 mm on the enamel surface of the buccal and lingual sides. The teeth were demineralised and were divided into four groups with 15 teeth in each group. The buccal window served as experimental and the lingual as control. The teeth were immersed in toothpaste slurry containing: sodium fluoride (Group A); sodium monofluorophosphate (Group B); stannous fluoride (Group C) and amine fluoride (Group D). The fluoride content in the etched superficial enamel layer in the windows was analysed using a fluoride ion-specific electrode. Results Within the parameters of this study, the uptake of fluoride was statistically significant in Group D (p \ 0.05). The uptake of fluoride by tooth enamel in an increasing order was Group A \ Group B \ Group C \ Group D. Conclusion The study showed that enamel treated with amine fluoride had the highest fluoride uptake. Keywords enamel
Fluoride dentifrice Remineralisation Tooth
Work attributed to Department of Pedodontics and Preventive Dentistry, SDM College of Dental Sciences and Hospital, Dharwad India. V. H. Patil (&) R. T. Anegundi Department of Pedodontics and Preventive Dentistry, KLE VK Institute of Dental Sciences, Nehru Nagar, Belgaum, Karnataka 590010, India e-mail: [email protected]
Introduction More than a century ago, research was started on the effect of fluoride on oral health. It was in the second half of the 20th century that the focus of the research was upon the development and evaluation of different fluoride formulations. The fluoride which is incorporated into the crystalline lattice of the dental hard tissues making it less soluble in acid environment has been the scientific basis for the prevention of dental caries. Continuous research confirm that topical fluoride application is more effective in caries prevention than systemic fluoride application. In vitro studies showed that topical fluoride application produced 20 times higher fluoride levels in the superficial layer of enamel and dentine than the initial fluoride content in deeper layers. A 20–40 % cariespreventive effect of topical fluoride agents was shown in clinical studies (Ripa 1990; ten Cate 1999; Clarkson 2000; Holler et al. 2002; Petersen and Lennon 2004). Among caries-preventive protocols, fluoride-containing dentifrices are well accepted (Arnold et al. 2006). Dentifrices have been widely adopted as the principle means of delivering topical fluoride around the world for caries-preventive benefits (Zero 2006). The bioavailability of fluoride is very important for the caries-preventive effect which in turn is dependent on the solubility of fluoride-containing compounds leading to the adhesion of that fluoride compound to the tooth surface. From in vitro studies, it is well known that inorganic and organic fluorides in tooth-paste systems cause markedly different uptake of fluoride on tooth enamel and have different influences on remineralisation (Arnold et al. 2006). Hence, the aim of this study was to evaluate and investigate the possible differences in fluoride uptake on tooth enamel from four different fluoride formulations in commercially available dentifrices.
123
Eur Arch Paediatr Dent
Fig. 1 Window measuring 4 9 4 mm
Fig. 2 Demineralised window
Materials and methodology
displayed demineralisation clinically as white chalky spots (Fig. 2). The lingual window was covered with an acid resistant nail varnish of different colour. The teeth were then immersed in different dentifrice slurries and incubated at 37 ° C for 2 days which simulates 2 years of tooth brushing twice daily for 2 min per day (Arnold et al. 2006). The pH of the slurries was evaluated prior to the immersion of the sample teeth. The pH was: 8.15, 9.43, 5.34 and 5.05 for groups A, B, C and D, respectively. The teeth were then washed with double de-ionised distilled water and dried. The acid biopsy technique was used for fluoride ion estimation. The samples were etched for 60 s in 10 ml of 0.5 M perchloric acid separately in the experimental window followed by the control window after cleaning the nail varnish from the control window with acetone. To this, 10 ml of total ionic strength adjustment buffer (TISAB-II) was added. The fluoride concentration in solution was determined with Orion 9609 BNWP fluoride ion-specific electrode (Thermo Scientific, USA) and expressed in mg/L (Table 1). The mean and standard deviation between the experimental and control windows of the various groups were compared using the independent samples t test while pairwise comparison of different groups was undertaken using the one-way ANOVA followed by post-hoc Tukey’s HSD test. The statistical significance was set at a p value of\0.05.
Sixty healthy human premolars extracted for orthodontic purposes were used as study samples. The teeth were cleaned for surface debris, calculus and periodontal tissue attachments by scaling and root planing, followed by pumice prophylaxis. The teeth were stored in double deionised distilled water until use. The teeth were then covered with an acid-resistant nail varnish leaving 4 9 4 mm window on the buccal and lingual surfaces of the crown (Fig. 1). The buccal window in each tooth served as the experimental window and the lingual window as the control. The teeth were then randomly divided into four groups, 15 teeth in each group and a control group within. The groups were: Group A (Colgate Total, ColgatePalmolive company, India) sodium fluoride dentifrice (NaF) 1,000 mg/L of F, Group B (Colgate Strong Teeth, Colgate-Palmolive company, India) sodium monofluorophosphate dentifrice (NaMFP) 1,000 mg/L of F, Group C (Sentium, Dent Aids, India) stannous fluoride dentifrice (SnF2) 1,000 mg/L of F and Group D (Amflor, Group Pharmaceuticals Limited, India) amine fluoride dentifrice (AmF) 1,000 mg/L of F. The teeth were demineralised in 500 ml solution containing 0.1 M lactic acid with 3 mM calcium chloride, 1.8 mM potassium dihydrogen phosphate and 40 % NaOH at a pH of 4.5 for 2 days at 37 °C in an incubator. The solution was changed every 12 h to avoid variation of the pH of the demineralising solution. After demineralisation, the teeth were cleaned thoroughly with double de-ionised distilled water. The windows
123
Results The uptake of fluoride by tooth enamel in the experimental windows of groups A, B, C and D with their respective
Eur Arch Paediatr Dent
control windows were statistically very highly significant (Table 1; Fig. 3). The p value of group A with respect to groups B, C and D was very highly significant. The p value of group B with groups C and D was also very highly significant. Whereas the p value of group C with group D was highly significant (Table 2). The results showed that the uptake of fluoride by tooth enamel was highest in samples treated with AmF toothpaste slurry when compared to the samples treated with SnF2, NaMFP and NaF toothpaste slurries.
Discussion The benefits of at-home topical fluorides in a wide variety of formulations such as mouth rinses, dentifrices, gels and solutions are universally encouraged by dental professionals and accepted by the community. Fluoride dentifrices have been proven effective anti-caries agents since 1955. Bibby put forward the idea that frequent application of fluoride from a dentifrice might provide an effective
Table 1 Comparison of experimental and control windows with fluoride uptake in different groups Groups Group A
Window
Meana
Experiment
10.3135
2.1721
7.4629
1.0753
14.1762
1.4140
Control Group B
Experiment Control
Group C Group D
SDa
*0.0001
7.7245
0.9950
Experiment
19.4428
1.4299
Control
10.0063
0.9080
*0.0000
Experiment Control
21.6793 9.3173
2.4559 1.4905
*0.0000
* indicates significance (p \ 0.05) a
p value
Fluoride values expressed in mg/L (equivalent to ppm F)
*0.0000
form of caries prophylaxis. Although earlier studies did not attend with success, they probably marked the start of the quest for effective fluoride dentifrice systems (Bibby 1945; Stewart et al. 1982). The observations of this study showed that there was uptake of fluoride by demineralised tooth enamel surfaces in the experimental windows compared to their respective controls. The uptake of fluoride in AmF group was statistically very highly significant when compared to other groups, the uptake of fluoride in SnF2 group was statistically very highly significant when compared to the group containing NaMFP and NaF and the uptake of fluoride in NaMFP group was statistically very highly significant than in the group containing NaF. It can be concluded from the above data that the samples treated with AmF showed the highest fluoride uptake in the tooth enamel followed by the ones treated by SnF2, and NaMFP, with NaF being the least. Similar results were seen in other studies with teeth treated using these dentifrices (Chan et al. 1991; Klimek 1998). The mean uptake of fluoride values was comparatively more in one study (Chan et al. 1991) than those found in the present study and this could be because of the higher strength of the fluoride solutions that were used, whereas the study by Klimek (1998) noticed lower fluoride uptake; this could be because they used an indirect method for fluoride estimation where some of the fluoride remained complexed (Chan et al. 1991; Klimek 1998). Studies on remineralisation of bovine enamel were evaluated after treating with NaF, AmF dentifrices and placebo solution. The results were in favour of AmF for remineralisation (Buchalla et al. 2002; ten Cate et al. 2008). However, one other study noticed no difference in uptake of fluoride between groups treated with AmF and NaF (Toda and Featherstone 2008). The SnF2 group showed a higher uptake of fluoride compared to the ones treated with NaMFP and NaF, and the group treated with NaMFP showed higher uptake of
Fig. 3 Showing the comparison of fluoride uptake in mg/L between experimental and control window among the four groups
123
Eur Arch Paediatr Dent Table 2 Pair-wise comparison of fluoride scores in the experimental windows of the four groups Group
Group A
Group B
Group C
Group A
–
Group B
*0.0002
–
Group C
*0.0002
*0.0002
–
Group D
*0.0002
*0.0002
*0.0124
Group D
–
* indicates significance (p \ 0.05)
fluoride compared to the group treated with NaF. In contrary to this, a previous study noticed a higher F uptake in NaF-based paste compared to NaMFP and SnF pastes (Reintsema et al. 1985). The sample treated with AmF showed the highest fluoride uptake in the tooth enamel followed by the ones treated with NaMFP and NaF. Several other studies have shown the fluoride uptake of demineralised human dental enamel to be significantly higher in groups treated with an AmF toothpaste (Klinger and Wiedemann 1986; To´th et al. 1998; Arnold 2006; Altenberger et al. 2010). However, two of these studies (To´th et al. 1998; Altenberger et al. 2010) noticed fluoride uptake by NaF toothpaste was higher than that found in NaMFP toothpaste, which was in contrast with the present study. This could be because NaF is ionically bonded, which appears to be critical for fluoride uptake, rather than the covalently bonded NaMFP toothpaste. However, in the present study, NaMFP group showed a higher F uptake which is consistent with a previous study (Arnold 2006). In this study, the pH of the toothpastes was evaluated prior to the immersion of the samples. It was noticed after treatment of the samples with their respective slurries that the uptake of fluoride was statistically very highly significant in groups treated with AmF and SnF2 when compared to groups treated with NaMFP and NaF. This can be attributed to the well-known fact that the reaction between enamel and fluoride is faster, and that fluoride uptake on and in enamel is higher at lower pH (Saxegaard and Rølla 1988; van Strijp et al. 1999; Altenberger et al. 2010). The highest uptake of fluoride was seen in the AmF group. AmF is an organic fluoride, whereas the other fluoride dentifrices used in the study are inorganic. The distribution of organic material is increased in demineralised enamel and this explains the higher uptake of organic fluoride. The cations in AmF, as in other surfactants, have a hydrophilic and a hydrophobic part. The electrostatic attraction holds the positively charged nitrogen atom and the negatively charged fluoride ions in close vicinity at the hydrophilic end. With its positive charge it can attach itself easily to the predominantly charged negatively charged
123
enamel surface. Thus, the hydrophobic part is aligned towards the oral cavity and the hydrophilic towards the tooth surface. Hence, the fluoride ions accumulate close to the tooth surface by this self-organised arrangement. Thus, the accumulated fluoride is available directly for the production of calcium fluoride as a labile reservoir or is available immediately for remineralisation. The surface layer of calcium fluoride is stabilised by the hydrophobic part of molecule pointing towards the oral cavity which reduces moistening by saliva and prevents it being washed out rapidly (Schmid 1983). On other hand, the other fluorides used in the present study are inorganic fluorides which are lost by way of ionic exchange in the saliva. Conclusion Dentifrices play an essential role in our daily oral hygiene maintenance. Fluoride deposition into partially demineralised enamel is one of the several important factors in the cariostatic activity of topical fluorides. The amount of fluoride present in the tooth enamel is an important component in caries prevention. This study evaluated the uptake of fluoride by tooth enamel by comparing dentifrices containing different fluoride formulations, i.e. NaF, NaMFP, SnF2 and AmF. It can be concluded that the uptake of fluoride was statistically highly significant with the group treated with AmF than with groups treated with other fluoride formulations. Some of the factors which may have influenced the observations found in this study are: variation in the initial fluoride levels in human teeth since they were collected from many individuals residing in different geographic locations and the fluoride level varies strongly with the location on the tooth surface. However, further detailed in vivo studies with larger sample size may be required for evaluating the uptake of fluoride on tooth enamel with different fluoride formulations in the dentifrice.
References Altenberger MJ, Bernhart J, Schicha TD, Wrbas KT, Hellwig E. Comparison of in vitro fluoride uptake from whitening toothpastes and a conventional toothpaste in demineralised enamel. Schweiz Monatsschr Zahnmed. 2010;120(1):104–8. Arnold WH, Dorrow A, Langenhorst S, et al. Effect of fluoride toothpastes on enamel demineralization. BMC Oral Health (serial online) 2006 June (cited 2006 June);6(8):(6 screens). http://www.biomedcentral.com/1472-6831/6/8. Bibby BG. A test of the effect of fluoride containing dentifrices on dental caries. J Dent Res. 1945;24:297–303. Buchalla W, Attin T, Schulte-Mo¨nting J, Hellwig E. Fluoride uptake, retention, and remineralization efficacy of a highly concentrated fluoride solution on enamel lesions in situ. J Dent Res. 2002;81(5):329–33.
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