Stannous-Containing clay as Anti-Erosion Material

Objectives: Stannous ions (Sn²⁺) have shown a protective effect against dental erosion, especially when combined with fluoride. Encapsulating Sn²⁺ in clay may allow for improved stability of the formulation, in addition to an increased release of this agent on demand (upon an acid challenge). This study aimed to encapsulate Sn²⁺ in bentonite clay particles and to test the release of this cation in both artificial saliva (pH=7.0) and acidic solution (0.3% citric acid, pH=2.6).
Methods: 10 g of bentonite was used for 200 ml of a SnCl₂ solution (800ppm Sn). The resulting solution was kept under stirring for 24h and then centrifuged (3000 rpm, 5 min). The supernatant was removed, and the mass was rinsed with distilled water and centrifuged again (3000 rpm, 5 min). To test the release of Sn²⁺ from the cation exchange clay, 1g of Sn²⁺-containing bentonite was added to 100ml of either artificial saliva or acid and kept under stirring. Aliquots of each solution were collected after 1, 3, 5, 12, 24 and 48h. Sn²⁺ release was analyzed by Optical Emission Spectrometry, in triplicates. Sn²⁺ data from saliva and acid were compared using student's t-test (α=0.05).
Results: In saliva, the means (SD) Sn²⁺ values (in mg/ml) were: 5.65 (0.32) for 1h; 5.12 (0.08) for 3h; 5.16 (0.17) for 5h; 4.40 (0.23) for 12h; 3.36 (0.10) for 24h; and 2.04 (0.07) for 48h. In acid: 14.19 (0.17) for 1h; 31.66 (0.24) for 3h; 22.30 (0.39) for 5h; 34.53 (0.09) for 12h; 37.15 (0.42) for 24h and 30.75 (0.10) for 48h. For all times, the release values in acid were higher than in saliva (p<0.001).
Conclusions: The bentonite particles were able to successfully store the active, allowing an increased release of Sn²⁺ under an acidic environment when compared to a neutral one, showing the potential to incorporate this product into dental materials against erosion.