Surface profilometry analysis (SPA)
Using the 2D surface profiler (Surtronic 3+ surface profiler, AMETEK Taylor Hobson company, LC, UK), the enamel specimens were measured for surface roughness (Ra) in μm using the stylus, with the cut-off length set at 0.25 mm. Randomly, 3 surface profilometric readings were taken per specimen, at each baseline and post-treatment/erosive cycle.