The subsurface lesion in erosive tooth wear.

ABSTRACT

OBJECTIVES: This study compared the surface change on natural and polished enamel exposed to a joint mechanical and chemical wear regimen. METHODS: Human enamel samples were randomly assigned to natural (n = 30) or polished (n = 30) groups, subjected to erosion (n = 10, 0.3% citric acid, 5 min), abrasion (n = 10, 30 s), or a combination (n = 10). Wear in the form of step height was measured with a non-contact profilometer, and surface changes were inspected with SEM on selected sections. Data was normalised and underwent repeated measures MANOVA, accounting for substrate and erosive challenge as independent variables, with Bonferroni correction for significant post hoc interactions. RESULTS: After four cycles, polished samples had mean step heights of 3.08 (0.40) µm after erosion and 4.08 (0.37) µm after erosion/abrasion. For natural samples, these measurements were 1.52 (0.22) µm and 3.62 (0.39) µm, respectively. Natural surfaces displayed less wear than polished surfaces under erosion-only conditions (p<0.0001), but the difference disappeared with added abrasion. SEM revealed a shallow subsurface layer for polished surfaces and natural ones undergoing only erosion. However, natural surfaces exposed to both erosion and abrasion showed deeper subsurface changes up to 50 µm. CONCLUSION: Natural enamel, when exposed to erosion alone, showed less wear and minimal subsurface alterations. But with added abrasion, natural enamel surfaces saw increased wear and notable subsurface changes compared to polished ones. CLINICAL SIGNIFICANCE: The pronounced subsurface lesions observed on eroded/abraded natural enamel surfaces highlight how combined wear challenges may accelerate tooth tissue loss.