Correlations between AFM and SEM imaging of acid-etched tooth enamel

Enamel bond strength is an important factor in restorative dentistry and crucially depends on the enamel roughness. To increase roughness, different etching procedures are employed and profilometric estimations, with probe profilometers, including atomic force microscopy (AFM), have been made. However, no correlation between roughness and bond strength has been found. To search for a possible error source leading to the underestimation of enamel roughness when utilizing probe profilometers, the authors compared scanning electron microscopy and AFM images of acid-etched tooth enamel. The results showed that AFM imaging cannot correctly depict the acid-etched enamel surface, because of the high steepness of the enamel crystallites and the generation of convolute images. This leads to a large underestimation of the profilometric parameters measured with AFM, or other profilometers, on acid-etched tooth enamel surfaces.