Enamel surface alterations after repeated conditioning with HCl.

BACKGROUND: The aim of this study was to investigate the influence of etching time with 15% hydrochloric acid (HCl) on the enamel surface destruction by studying the resulting roughness and erosion depth. METHODS: The vestibular surfaces of 12 extracted, caries free human incisors were divided into four quadrants, and each quadrant was etched with 15% HCl for different numbers of etching cycles (1×2, 2×2, 3×2 and 4×2 min). Surface roughness and erosion depth were measured quantitatively with optical profilometry, and the surface morphology was imaged with scanning electron microscopy (SEM). RESULTS: After two minutes of 15% HCl application a median enamel substance loss of 34.02 µm was observed. Lengthening of etching time (2×2, 3×2 and 4×2 min) resulted in significantly increase in erosion depth to each additionally, between 13.28 -15.16 µm (p < 0.05) ending up in a total median enamel surface loss of 77 µm. Regarding surface roughness no significant (p > 0.05) difference was found between unetched enamel and the etched enamel surfaces. CONCLUSION: Repeated 15% HCl conditioning of the enamel surface increases the depth of the etched surface erosion. However, the total erosion depth is rather shallow and therefore negligible.