Nano and micro scale analysis of dentin with in vitro and high speed atomic force microscopy

Atomic force microscopy (AFM) has proven useful in the investigation of porous surfaces due to its nanoscale spatial resolution, micron scale range, compatibility with nonconducting materials, and even applicability ability to biological systems since it can operate in fluids. Since AFM directly measures the surface by contact, it is particularly suited for quantifying the roughness, and more appropriately for porous and particulate materials, the surface area. In this work, a multi-scale porous material, human molar dentin, was studied with AC mode AFM (both in-air and in-liquid), enabling extensive analyses both for plain dentin as well as specimens exposed to nanoparticle TiO2 containing toothpaste to approximate personal dental hygiene. Finally, high speed AFM is also demonstrated in vitro with equivalent results, except that the time required per image is reduced by several orders of magnitude from tens of minutes to as little as 6 s. Careful implementation of AFM, both at standard and high speeds, is therefore effective for investigating highly porous materials, including biological tissue, in environmentally or physiologically relevant conditions.