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

Abstract

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 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 (ΔE) were measured spectrophotometrically. Group (a) showed a significant increase in color changes with respect to whitening after one cycle (mean ΔE = 5.4 [±2.66], p ≤ 0.006) and three cycles (mean ΔE = 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 ΔE = 2.77 [±1.01], p = 0.02) and nine cycles (mean ΔE = 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.

Whitening Effects of a Novel Oral Care Gel with Biomimetic Hydroxyapatite: A 4-Week Observational Pilot Study

“…The brightness of the teeth increased as well ( p = 0.9, 95% CI: (0.46; 1.29)). Taken together, this confirms results from in vitro studies that demonstrated tooth-whitening properties of calcium phosphates like hydroxyapatite [ 27 , 28 , 29 ], suggesting that hydroxyapatite is a promising whitening agent [ 6 , 29 ].…”

“…The whitening effect of biomimetic hydroxyapatite can be explained by: the formation of a white mineral (protective) layer on the enamel surface [ 24 , 26 , 29 ], the remineralization of enamel lesions (i.e., resulting in a smoother enamel surface) [ 7 , 8 , 9 ], and the reduction of plaque formation and exogenous stains (i.e., as a consequence, the incorporation of colorants into plaque and calculus is reduced) [ 1 , 4 , 13 ]. …”

“…Several in vitro and in situ studies have analyzed the interaction of biomimetic hydroxyapatite particles with enamel surfaces [ 1 , 24 , 25 , 26 ]. This interaction can lead to a tooth whitening effect [ 6 ], which has been shown in different in vitro [ 27 , 28 , 29 ] and in vivo studies [ 17 , 30 , 31 ]. Unlike peroxide-based products which may induce side effects (e.g., bleaching sensitivity and damage of the organic matrix of enamel and dentin), hydroxyapatite can be used on a daily basis without any adverse reactions, and even from persons under the age of 18 [ 22 ].…”

“…Hydroxyapatite, the active ingredient, can be used, for example, in toothpastes [ 2 , 3 , 4 , 8 ] and mouthwashes [ 1 , 24 ]. Additionally, hydroxyapatite is commercially available at higher concentrations in gels to enhance the effects of daily tooth brushing [ 9 , 11 , 29 , 33 ]. Recent in vitro studies show that a newly developed hydroxyapatite gel has significant whitening [ 29 ] and enamel remineralizing effects [ 9 ] as well as erosion protective properties [ 33 ].…”

“…Additionally, hydroxyapatite is commercially available at higher concentrations in gels to enhance the effects of daily tooth brushing [ 9 , 11 , 29 , 33 ]. Recent in vitro studies show that a newly developed hydroxyapatite gel has significant whitening [ 29 ] and enamel remineralizing effects [ 9 ] as well as erosion protective properties [ 33 ]. Amaechi et al, for example, showed that this hydroxyapatite-gel is as effective as a highly concentrated fluoride gel with 12,500 ppm fluoride regarding remineralization of early caries lesions [ 9 ].…”