archives of oral biology 59 (2014) 621–624

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Effect of experimental mouthrinses containing the combination of NaF and TiF4 on enamel erosive wear in vitro B.M. Souza, L.L.M. Lima, L.P. Comar, M.A.R. Buzalaf, A.C. Magalha˜es * Department of Biological Sciences, Bauru School of Dentistry, University of Sa˜o Paulo, 17012-901 Bauru, SP, Brazil

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Objective: This study analysed the anti-erosive effect of experimental solutions containing

Accepted 20 March 2014

TiF4 and NaF. Methods: Bovine enamel samples (n = 15) were treated with: (1) commercial solution with


SnCl2/NaF (Erosion Protection1); (2) experimental solution with 0.0815% TiF4; (3) 0.105% NaF;


(4) 0.042% NaF + 0.049% TiF4; (5) 0.063% NaF + 0.036% TiF4 or (6) control. The samples were


submitted to pH cycles and daily fluoride applications for seven days. The enamel wear was

Titanium tetrafluoride

measured using a contact profilometer and analysed by ANOVA ( p < 0.05).

Sodium fluoride

Results: The best anti-erosive effect was found for experimental solution with 0.0815% TiF4

Stannous fluoride

(99% reduction in enamel wear), followed by SnCl2/NaF (78%) and 0.049% TiF4 + 0.042% NaF solution (41%). Conclusions: The experimental solution containing a specific combination of TiF4 + NaF has the ability to partially reduce enamel erosion. # 2014 Elsevier Ltd. All rights reserved.



Fluoride has been the approach of the researchers worldwide to control and reduce the enamel erosive wear progression.1,2 It is already known that conventional fluorides, such as sodium fluoride, have the potential to reduce erosive demineralisation due to the formation of calcium fluoride (CaF2) like-layer.3 This layer acts as a physical barrier hampering contact of the acid with the underlying enamel and also as a mineral reservoir. Subsequently, calcium and fluoride released can increase the saturation level regarding dental apatite promoting mineral precipitation.1 However, the CaF2 like-layer presents low acid resistance3 and its effect require high concentration and frequent application.4 * Corresponding author. Tel.: +55 14 32358497; fax: +55 14 32358497. E-mail addresses: [email protected], [email protected] (A.C. Magalha˜es). 0003–9969/# 2014 Elsevier Ltd. All rights reserved.

On the other hand, polyvalent metal fluorides, such as stannous fluoride (or a combination of SnCl2 + NaF) or titanium tetrafluoride, are more effective against enamel erosion.5–7 The mode of action of tin-containing fluoride solutions is related to the formation of a surface rich of metal precipitates [Ca(SnF3)2, SnOHPO4, Sn3F3PO4], which has been shown to have higher acid resistance than particles of CaF2.7,8 The mechanism of action of titanium tetrafluoride is due to the effect of both fluoride and titanium. Titanium tetrafluoride reacts with apatite, by dissolution and precipitation, due to its low pH, leading to a formation of a layer rich in calcium fluoride, titanium dioxide and titanium hydrogen phosphate hydrate.9,10 The layer produced by TiF4 has been shown to be more acid resistant compared to SnF2 solution.5,6


archives of oral biology 59 (2014) 621–624

The efficacy of TiF4 is highly dependent on it low pH,11,12 but the low pH of TiF4 solution does not allow self-application by the patient as a mouthrinse. It is speculated that the low pH of TiF4 could have some cytotoxicity effect on fibroblast.13 However, the side effect of TiF4 needs to be confirmed. In order to reduce the possibility of side effects by the application of polyvalent metal fluorides, the combination of SnCl2 and NaF has been tested, taking the advantage of the metal ions without the negative effect of low pH in the oral mucosa.14 The combination of fluoride and tin has been shown effective compared to NaF7,14,15; however, there is no information about the difference in the performance between TiF4 and SnCl2/NaF on enamel erosion. Furthermore, it would be interesting to test whether the combination of TiF4 and NaF could increase the pH of the solution, keeping its effect against enamel erosion and allowing its use as a mouthrinse by the patient. Therefore, the aim of this study was to test the efficacy of experimental mouthrinse solutions composed of two combinations of TiF4 and NaF compared to TiF4 alone and the commercial solution containing SnCl2/NaF on enamel erosion in vitro. The null hypothesis was that there is no difference on the anti-erosive performance among the different fluoride solutions.


Materials and methods


Samples preparation

Ninety crowns of bovine incisors, which were previously maintained in 0.1% thymol solution, were embedded in acrylic resin. The labial surfaces were ground flat and polished with water-cooled silicon carbide discs (320, 600, and 1200 grades of Al2O3 papers; Buehler, Lake Bluff, IL, USA). This procedure removed about 200–300 mm of enamel. The references areas on the polished enamel surface were marked with two parallel lines made with a scalpel blade, 1.5 mm apart. Small drilling was also done on the outer area of the enamel surface to allow the correct position of the sample in the profilometric system. Baseline scans were obtained with a contact profilometer (Mahr Perthometer, Go¨ttingen, Germany). The inclusion criterion of the samples was the baseline profile, where samples with irregular or inclined profile were excluded. Prior to the experiment, 2/3 of the samples surface were protected with red nail varnish, leaving only 1/3 central of enamel surface exposed to erosive challenges and treatment. The samples were randomly divided into six groups (n = 15) and stored in water until being used for the experiment.


pH cycling and fluoride treatment

The samples were submitted to a pH cycling model for seven days. Erosive challenges took place four times a day by immersion in a soft drink (Sprite Zero, pH 2.6) for 90 s each in a container with 30 ml of the erosive solution per sample at 25 8C. Between each erosive challenge (2 h) and overnight, the samples were exposed to artificial saliva (pH 6.8, 30 mL/ sample). The saliva was composed of the following reagents (v = 500 mL): 0.001 g ascorbic acid, 0.015 g glucose, 0.29 g NaCl,

0.085 g CaCl2, 0.08 g NH4Cl, 0.635 g KCl, 0.08 g NaSCN, 0.165 g KH2PO4, 0.1 g carbamide and 0.17 g Na2PO4. Two times a day (immediately after the first and last erosive challenge), the treatment was done (v = 0.5 ml/sample) for 1 min following the groups: (1) commercial solution with SnCl2/NaF (800 ppm Sn+2, 500 ppm F , pH 4.5, Erosion Protection1, GABA Int. AG, Switzerland, positive control); (2) 0.0815% TiF4 (315 ppm Ti4+, 500 ppm F ); (3) 0.105% NaF (475 ppm F , pH adjusted to 4.5 with 5 M phosphoric acid, similar to the commercial control); (4) 0.042% NaF and 0.049% TiF4 (NaF: 190 ppm F ; TiF4: 190 ppm Ti4+ and 300 ppm F ); (5) 0.063% NaF and 0.036% TiF4 (NaF: 285 ppm F ; TiF4: 140 ppm Ti4+ and 220 ppm F ); (6) no treatment (negative control). All solutions have approximately 500 ppm F . After the treatment, the excess of solution was removed using cotton swab. The experimental fluoride solutions were prepared using the analytical grade reagents from Sigma–Aldrich and their pH was measured.



Enamel erosive wear was determined using a contact profilometer (Mahr Perthometer, Go¨ttingen, Germany). Prior to the experiment, five equidistant baseline surface scans of each sample were performed (5 mm of reading, 250 mm a part). For the determination of enamel erosive wear, the nail polish was removed after the experiment. Thereafter, five profiles were recorded at exactly the same sites as the baseline measurement. To achieve this outcome, the enamel samples presented the identification marks (small drillings made with drill 1/4) and were inserted into a metal device, to allow the stylus to be accurately repositioned at each measurement. Baseline and final profiles were done and compared using the software MahrSurf CXR20. The scans were superposed and the average depth of the under curve area was calculated (mm).


Statistical analysis

GraphPad Software (San Diego, USA) was used for the statistical analysis. It was checked if the data presented a normal distribution and homogeneity (Kolmogorov–Smirnov and Bartlett tests, respectively). Once the homogeneity was not achieved, the data were transformed into log and analysed using one-way ANOVA followed by post hoc Tukey‘s test. The level of significance was set at 5%.



The best anti-erosive effect was found for 0.0815% TiF4 solution (99% reduction of enamel wear), followed by Erosion Protection1 (78% reduction) and the combination of 0.042% NaF + 0.049% TiF4 solution (41% reduction) compared to control ( p < 0.0001). The solutions containing only NaF and the combination of 0.063% NaF + 0.036% TiF4 did not differ from control ( p > 0.05). Table 1 shows the pH values and the mean of enamel wear presented by the different groups. The combination of NaF + TiF4 was able to increase the pH (Table 1), but its effect against enamel erosion was reduced. Therefore, the null hypothesis was rejected.

archives of oral biology 59 (2014) 621–624

Table 1 – pH values and the mean and S.D. of enamel wear presented by the different groups (mm).

Erosion Protection1 SnCl2 + NaF (positive control) TiF4 (0.0815%) NaF (0.105%) NaF + TiF4 (0.042% + 0.049%) NaF + TiF4 (0.063% + 0.036%) Negative control


Mean  S.D.


0.75  0.18 b

2.5 4.5 4.4 4.5

0.03  0.04 a 2.93  0.42 d 1.97  0.90 c 3.51  0.76 d 3.34  0.94 d

Different letters show significant differences among the groups (ANOVA, p < 0.0001).



Previous studies have shown that the effect of TiF4 against enamel erosion is dependent on the concentration12 and the low pH,11,12 which is in agreement with the data of this work, in which pure TiF4 solution, more concentrated in terms of titanium and presenting the lowest pH value, showed nearly 100% protection against enamel wear. Furthermore, we have shown that TiF4 was superior to NaF alone, confirming previous data.1,5,6,16 However, there is no previous study comparing TiF4 solution and the commercial solution Erosion Protection1. Our results are interesting, since the TiF4 solution was better than the positive control, suggesting that the titanium precipitates might be more acid resistant than tin precipitates.5,6 The original idea of the study was to combine two fluorides salts in an experimental solution so that it was possible to deliver TiF4 at a pH more suitable for the daily use. The combination of fluorides led to rise in the pH values, which was similar to the value found in the commercial solution Erosion Protection1. However, the efficacy against enamel erosion was reduced by the combination of TiF4 and NaF, probably due to the reduction of titanium precipitation on enamel. Only a specific combination of TiF4 and NaF was still presenting some significant anti-erosive effect, but inferior to TiF4 alone and the commercial fluoride solution. The fluoride concentration tested in this work was lower than those from previous studies,11,12,16 just to allow the daily application by the patient (at the morning and at evening, 1 min of mouthwash). Highly concentrated fluoride is indicated for professional application, as performed by Hove et al.12 who tested the concentration of 0.5 M fluoride and achieved 90% reduction in enamel erosion by a single application of TiF4 after a period of 6 min of erosion. On the other hand, patients suffering from erosion could be benefit by the daily application of TiF4, as these patients are often exposed to erosive attacks, as performed in the present experimental protocol (four times of 90 s erosion/day). In our study, the twice daily application of 0.0815% TiF4 reduced almost 100% enamel wear after 42 min of erosion, which seems to be very promising. Vieira et al.16 showed that daily application of 0.5% TiF4 was more effective than a single application after 48 min of erosion. In this study, the daily fluoride application improved in 69% the reduction of wear compared to a single application.16 This overview of the


literature reinforces the benefits of the daily fluoride application at least for the control of enamel erosion in vitro. Based on the present findings, the effect of the experimental solution containing 0.042% NaF + 0.049% TiF4 should be further tested using an in situ and in vivo models to confirm the present data. The frequency of fluoride application and the effect of different erosive challenges should be included as factors to be tested in the future. A recent in situ study pointed out that the daily application of 0.4% SnF2 and 0.15% TiF4 reduced in 94% and 90% the enamel wear after 36 min of erosion.2 On the other hand, Hjorstjo¨ et al.17 applied an in vivo model, in which a single application of different fluorides was done on incisors, with a subsequent erosive attack (5 min). These authors showed that solutions containing HF and SnF2 were better than TiF4 and NaF in reducing calcium release, which in part contradicts the results obtained in our study. Therefore, to prove our data, there is a need to carry out in situ and in vivo studies for a better understanding of the differences in the anti-erosive performance of the solutions with different fluoride combinations. In conclusion, the experimental mouthrinse solution containing a specific combination of TiF4 and NaF has the ability to partially reduce enamel erosion in vitro. However, the best preventive effect was still found for pure TiF4.

Funding PIBIC/USP for the concession of scholarship to the second author.

Competing interest None declared.

Ethical approval This in vitro study did not need the approval of the Local Ethical Committee.

Acknowledgment We thank PIBIC-USP for the concession of a scholarship to the second author.


1. Magalha˜es AC, Wiegand A, Rios D, Buzalaf MAR, Lussi A. Fluoride in dental erosion. Monogr Oral Sci 2011;22:158–70. 2. Stenhagen KR, Hove LH, Holme B, Tveit AB. The effect of daily fluoride mouth rinsing on enamel erosive/abrasive wear in situ. Caries Res 2013;47(1):2–8. 3. Ganss C, Schlueter N, Klimek J. Retention of KOH-soluble fluoride on enamel and dentine under erosive conditions – a comparison of in vitro and in situ results. Arch Oral Biol 2007;52(1):9–14.


archives of oral biology 59 (2014) 621–624

4. Ganss C, Klimek J, Brune V, Schu¨rmann A. Effects of two fluoridation measures on erosion progression in human enamel and dentine in situ. Caries Res 2004;38(6):561–6. 5. Hove L, Holme B, Øgaard B, Willumsen T, Tveit AB. The protective effect of TiF4, SnF2 and NaF on erosion of enamel by hydrochloric acid in vitro measured by white light interferometry. Caries Res 2006;40(5):440–3. 6. Hove LH, Holme B, Young A, Tveit AB. The protective effect of TiF4, SnF2 and NaF against erosion-like lesions in situ. Caries Res 2008;42(1):68–72. 7. Ganss C, Neutard L, von Hinckeldey J, Klimek J, Schlueter N. Efficacy of a tin/fluoride rinse: a randomized in situ trial on erosion. J Dent Res 2010;89(11):1214–8. 8. Barbcock FD, King JC, Jordan TH. The reaction of stannous fluoride and hydroxyapatite. J Dent Res 1978;57(9–10): 933–8. 9. Comar LP, Souza BM, Grizzo LT, Buzalaf MAR, Magalha˜es AC. Sound and demineralised enamel treated with TiF4 in vitro: KOH-soluble fluoride deposition and SEM-EDXS analysis. Caries Res 2013;47(sp. Issue):516. 10. Magalha˜es AC, Comar LP, Al-Ahj LP, Silva TL, Buzalaf MAR. Synthesis and characterization of hydroxyapatite treated with TiF4 in vitro. Caries Res 2013;47(sp. Issue):515.

11. Wiegand A, Waldheim E, Sener B, Magalha˜es AC, Attin T. Comparison of the effects of TiF4 and NaF solutions at pH 1.2 and 3.5 on enamel erosion in vitro. Caries Res 2009;43(4):269–77. 12. Hove LH, Holme B, Stenhagen KR, Tveit AB. Protective effect of TiF(4) solutions with different concentrations and pH on development of erosion-like lesions. Caries Res 2011;45(1):64–8. 13. Sen BH, Kazemi RB, Spa˚ngberg LS. Morphologic effects on L929 fibroblasts of titanium tetrafluoride application. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86(3):341–6. 14. Schlueter N, Klimek J, Ganss C. Efficacy of tin-containing solutions on erosive mineral loss in enamel and dentine in situ. Clin Oral Investig 2011;15(3):361–7. 15. Schlueter N, Neutard L, von Hinckeldey J, Klimek J, Ganss C. Tin and fluoride as anti-erosive agents in enamel and dentine in vitro. Acta Odontol Scand 2010;68(3):180–4. 16. Vieira AM, Ruben JL, Bronkhorst EM, Huysmans MC. In vitro reduction of dental erosion by low-concentration TiF4 solutions. Caries Res 2011;45(2):142–7. 17. Hjortsjo¨ C, Jonski G, Thrane PS, Saxegaard E, Young A. The effects of acidic fluoride solutions on early enamel erosion in vivo. Caries Res 2009;43(2):126–31.

Effect of experimental mouthrinses containing the combination of NaF and TiF4 on enamel erosive wear in vitro.

This study analysed the anti-erosive effect of experimental solutions containing TiF4 and NaF...
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