Evaluating Demineralization and Mechanical Properties of Human Dentin With AFM

Atomic force microscopy (AFM) is a valuable technique for the study of demineralization and the effects of other solutions and environments on the structure of human dentin because high-resolution studies of changes in structure and dimensions are possible in nearly any environment over time (1 ). Because dentin forms the bulk of the tooth and is subject to a variety of alterations as a result of disease, age, and treatment (1 ), such studies are useful for understanding the basic structure—property relations of dentin and for evaluation of various conservative and restorative dental treatments. Initial studies of demineralization and dehydration of dentin were reported in 1993 (2 ,3 ) in which relative changes in dimensions were used to evaluate these processes. It soon became apparent that a stable reference layer on the surface or embedded in the specimen would be most desirable for evaluation of time-dependent changes and to take advantage of the high-resolution capabilities of the AFM. In 1995, the use of paint-on varnish or photoresist (4 ) and evaporated gold layers (5 ) were developed that allowed evaluation of demineralization, either continuously or sequentially, for a variety of demineralizing agents. An additional technique of interest is the use of AFM-based nanoindention for measurements of site-specific hardness and elastic modulus of dentin. Such measurements can frequently be performed as a portion of the same study in which demineralization experiments are conducted.