Atomic force microscopy of acid effects on dentin.

Atomic force microscopy (AFM) was used in the examination of the early stages of acid treatment of dentin. Disks of highly polished dentin were initially examined under deionized water and following exposure to 0.025 M nitric acid for 20 s intervals from 0-100 s. Peritubular depth changes were linear (0.005 microns/s). The intertubular dentin surface initially moved at approximately 1/2 the peritubular rate and then reached a plateau as the demineralized collagen scaffold collapsed. There was no apparent difference in the tubule center-to-center distance during the treatment. Differences in the movement and morphology of the zones are of importance in dentin bonding applications relying on penetration of the demineralized dentin by adhesive monomers. The changes are probably related to the partial collapse of the collagen matrix. Alternatively, access to the apatite crystals and solubility may be higher in the peritubular zone. AFM appears to hold exceptional promise for the study of conditioning and priming agents for dentin bonding.