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. 2025 Jun 23;11(7):486.
doi: 10.3390/gels11070486.

The Influence of Calcium Ions and pH on Fluoride Release from Commercial Fluoride Gels in an In Vitro Study

Paweł J Piszko  1 , Michał Kulus  2 , Aleksandra Piszko  3 , Jan Kiryk  4 , Sylwia Kiryk  3 , Julia Kensy  5 , Agata Małyszek  6 , Mateusz Michalak  7 , Wojciech Dobrzyński  8 , Jacek Matys  4 , Maciej Dobrzyński  3
Affiliations

The Influence of Calcium Ions and pH on Fluoride Release from Commercial Fluoride Gels in an In Vitro Study

Paweł J Piszko et al. Gels. .

Abstract

Fluoride gels are widely used in dental prophylaxis due to their proven ability to prevent demineralization and promote remineralization of hard dental tissues. However, the effectiveness of fluoride release from such gels may be significantly influenced by environmental factors such as pH and the presence of calcium ions. This in vitro study aimed to evaluate how these variables affect fluoride ion release from three commercially available fluoride gels-Clarben, Flairesse, and Lunos. The gels were incubated in artificial saliva of varying pH levels (4.5, 6.0, 7.0, and 7.5) with and without the addition of calcium, as well as in other water-based media-tap water, deionized water, and 0.9% NaCl solution. Fluoride release and changes in pH were measured and statistically analyzed using a multifactorial ANOVA. The results revealed that fluoride release was highest in calcium-free environments and at neutral to slightly alkaline pH, while the presence of calcium significantly reduced fluoride availability. Among the tested products, Flairesse and Lunos exhibited sensitivity to calcium's presence, unlike Clarben. Fluoride release was generally higher in water than in artificial saliva. Additionally, all gels induced a decrease in pH, which varied depending on the initial pH and calcium content. These findings underline the importance of environmental conditions in optimizing the clinical efficacy of fluoride gel applications.

Keywords: calcium interference; dental biomaterials; fluoride gels; fluoride release; in vitro incubation; statistical analysis.

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Conflict of interest statement

The authors declare no conflicts of interest. Specifically, no conflict of interest or received financial support is declared from the manufacturers of the commercial products used.

Figures

Figure 1
Figure 1
Multimodal operation of fluoride gels in dentistry (created with Freepik.com).
Figure 2
Figure 2
The box plots depict the difference between the initial saliva pH and the pH measured after the gel was applied. Boxes marked with different letters are statistically different (p < 0.01 in the Tukey post hoc test), while those with at least one letter in common are not significantly different. The post hoc test included pairwise comparisons of all possible combinations of initial pH, gels, and the presence of Ca2+.
Figure 3
Figure 3
The box plots depict the concentration of fluoride released after gel application. Boxes marked with different letters are statistically different (p < 0.01 in the Tukey post hoc test), while those with at least one letter in common are not significantly different. The post hoc test included pairwise comparisons of all possible combinations of initial pH, gels, and the presence of Ca2+.
Figure 4
Figure 4
Box plots depicting fluoride release in artificial saliva and water. Boxes marked with different letters are statistically different (p < 0.01 in the Tukey post hoc test), while those with at least one letter in common are not significantly different. The post hoc test included pairwise comparisons of all possible combinations of initial pH, gels, and the presence of Ca2+.
Figure 5
Figure 5
Clarben, Flairesse, and Lunos—commercial fluoride gels evaluated in the study.
Figure 6
Figure 6
Bio Vortex V1 (A), 9609 Orion selective electrode and CPI-551 processing unit (B), and ESAgP-303W electrode connected to CPI-505 pH meter (C).
See this image and copyright information in PMC

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