AFM Evaluation of Etched Enamel Treated with Calcium-Containing Toothpaste

Atomic Force Microscopy in contact mode has previously been demonstrated to provide a visual and measurable method of assessing the surface topography of etched enamel. An experimental calcium-containing two-phase baking soda-toothpaste has been designed to mineralize surface defects in enamel and thereby increase surface smoothness and enhance gloss. Objective: This study was designed to evaluate Atomic Force Microscopy (AFM) as a means of measuring the ability of the toothpaste to smooth etched enamel. Method: A polished enamel core was etched by soaking in 100ml of an acidic beverage for 1hr. The specimen was subjected to 15 successive, 5min treatments with a 1:2 slurry of the two-phase toothpaste in water. The enamel was rinsed between treatments with distilled water. The AFM was used to make graphic images of the surfaces and to measure surface roughness before and after each set of 5 successive treatments. Results: The AFM successfully shows the characteristic eroded prisms of etched enamel becoming shallower as new mineral is deposited. Prior to treatment the peak-to-valley depth was 1500nm. This dropped to under 500nm with successive sets of treatments. The surface roughness, Ra, decreased from 200 to about 100. Conclusions: The AFM is capable of detecting surface mineralization due to treatment with the calcium-containing two-phase baking soda-toothpaste.