Aspartic acid-facilitated remineralization: a bio-inspired alternative to fluoride for enamel repair

Dental enamel is constantly challenged by acidic conditions that disrupt the balance between demineralization and remineralization. Despite proven efficacy, current remineralization strategies face limitations, which prompt exploration of novel biomimetic approaches. Aspartic acid, a calcium-binding amino acid abundant in enamel matrix proteins, was hypothesized to serve as a potential enhancer of enamel remineralization. This study investigates its potential in combination with calcium sources, comparing the efficacy of these formulations to fluoride as a conventional market benchmark.

The remineralization potential of the experimental formulations was evaluated using a standardized in vitro bovine enamel model quantified by surface microhardness recovery (%SMHR). Polished enamel samples were subjected to demineralization in acidic conditions (pH = 4.5) for 60 min, in a solution containing 50 mM acetic acid, 2.2 mM calcium nitrate, 2.2 mM potassium phosphate monobasic and 0.1 ppm sodium fluoride. After rinsing with deionized water to arrest acid activity, the demineralized samples were incubated with solutions containing aspartic acid, calcium sources, their combinations and fluoride (as positive control) for 16 h at 37 °C. Enamel surface microhardness was measured before and after treatment to assess remineralizing effectiveness of test systems.

While 0.5% aspartic acid alone caused enamel demineralization (mean %SMHR = -37.32 ± 24.64), its combinations with calcium sources outperformed fluoride: 0.5% Asp + 1% tricalcium phosphate system demonstrated a mean %SMHR of 42.03 ± 19.45 - significantly higher than fluoride (14.12% ± 13.40%; p = 0.0181), a system of 0.5% Asp + 1% dicalcium phosphate dihydrate in another experiment achieved a mean %SMHR of 45.43 ± 14.64- also significantly superior to fluoride (5.15% ± 4.84%, p = 0.0058). Other formulations of Asp with calcium sources showed remineralizing potential but lacked statistical superiority to fluoride.

These results suggest that aspartic acid-calcium formulations may offer potential advantages over fluoride-based approaches in promoting enamel remineralization. However, further investigation is needed to elucidate the underlying mechanisms and establish clinical efficacy.