Quantitative and spectroscopic assessment of early-stage enamel erosion induced by popular acidic beverages

This study aimed to evaluate the initial effects of Coca-Cola, Red Bull, their sugar-free variants, and bottled orange juice on enamel surface roughness and mineral content.

Fifty-five sound human premolars were sectioned, mounted in resin, and polished to expose standardized enamel surfaces. After quality control, 75 samples (15 per group) were randomized and immersed in artificial saliva before submersion in acidic beverages (Coca-Cola, Red Bull, their sugar-free variants, and bottled orange juice) for 5 min. Surface roughness (Ra, Rq, Rz, Rv) was measured using optical profilometry, while Fourier Transform Infrared Spectroscopy (FTIR) analysis assessed mineral composition. The pH, titratable acidity, and buffering capacity of the beverages were also evaluated. Statistical analysis included paired t-tests, Wilcoxon signed-rank, Kruskal-Wallis, and ANOVA tests with p < 0.05 considered significant.

Coca-Cola showed the lowest pH (2.36 ± 0.05) while bottled orange juice had the highest (3.68 ± 0.03). Red Bull exhibited the highest titratable acidity (TA) (10.93 ± 1.17 mL NaOH) and buffering capacity (β) (2.97 ± 0.36), followed by orange juice (TA = 10.00 ± 0.40 mL; β = 2.97 ± 0.05). All beverages significantly increased surface roughness parameters (Ra, Rq, Rz; p < 0.05) except Rv for Coca-Cola (∆Rv= -0.23 ± 0.50, p = 0.094) and Coca-Cola Light (∆Rv=-0.34 ± 0.78, p = 0.114). Red Bull caused the greatest roughness changes (∆Ra= -0.12 ± 0.07, p < 0.001). FTIR revealed that Coca-Cola significantly elevated the PO₄ signal (ΔPO₄ = - 9.996 ± 17.305, p = 0.050), while Coca-Cola Light (∆Amide I = + 9.88 ± 17.39, p = 0.045) and Sugar-Free Red Bull (∆Amide I = + 50.25 ± 46.14, p = 0.001) decreased Amide I FTIR signal. Red Bull altered both PO₄ (∆PO₄= -1.72 ± 2.15, p = 0.008) and Amide I signals (∆Amide I = + 26.21 ± 37.80, p = 0.018). Orange juice showed no significant changes in any parameter (p > 0.05). Kruskal-Wallis tests confirmed significant differences between-group in post-exposure Amide I, Peak PO₄, mineral-to-matrix, and CO₃/PO₄ ratios (p < 0.05).

This study demonstrates that all tested beverages increased enamel surface roughness within minutes, with energy drinks causing the most severe effects. While colas and energy drinks altered both surface and chemical properties, bottled orange juice affected only surface topography without detectable mineral changes. These distinct erosion patterns suggest that different beverages may require tailored preventive strategies.