In Vitro Whitening Effect of a Hydroxyapatite-Based Oral Care Gel

Objective Oral care formulations aim to prevent oral diseases such as dental caries and gingivitis. Additionally, desire for white teeth still exists across all age groups. It is known that most whitening toothpastes are highly abrasive and can be harmful to teeth and gingiva. Therefore, a gel formulation with biomimetic hydroxyapatite (HAP; Ca5[PO4]3[OH]) as active ingredient was developed. This formulation was tested with respect to its tooth whitening properties in an in vitro study. Materials and Methods Enamel samples were allocated to either group (a) HAP gel, (b) whitening mouth rinse with phosphates, or (c) negative control (distilled water). Test products were applied by finger (a) or were rinsed (b, c) for 1, 3, and 9 (b and c only) cycles, respectively. Results Color changes (DE) were measured spectrophotometrically. Group (a) showed a significant increase in color changes with respect to whitening after one cycle (mean DE = 5.4 [±2.66], p < 0.006) and three cycles (mean DE = 11.2 [±3.11], p < 0.0001) compared to groups (b) and (c). For group (b), a significant increase in color change was measured after three (mean DE = 2.77 [±1.01], p = 0.02) and nine cycles (mean DE = 3.27 [±1.61], p = 0.006) compared to (c). Group (c) showed only minor and statistically insignificant color changes. Conclusion This in vitro study demonstrated a significantly higher ad hoc whitening effect of the HAP gel compared to the mouth rinse and water after short-time application.