Atomic force microscopy studies of crystal surface topology during enamel development

During the secretory stage of enamel development, the hydroxyapatite crysta ls appear as thin ribbons which grow substantially in width and thickness d uring the later maturation stage. In this study, the atomic force microscop e (AFM) was used to investigate developmentally-related changes in deprotei nized enamel crystal surface topography in normal animals and in those rece iving daily doses of fluoride, The AFM revealed previously undescribed surf aces features, some of which may represent growth sites or different crysta lline phases. Secretory stage crystals had greater surface rugosity and wer e more irregular, with spherical sub-structures of 20-30 nm diameter arrang ed along the "c"-axis, Maturation stage crystals were smoother and larger b ut revealed both subnanometer steps and lateral grooves running parallel to the "c"-axis, Crystals from fluorotic tissue showed similar features but w ere more irregular with a higher degree of surface roughness, suggesting ab normal growth. The AFM may prove an important adjunct in determination of t he mechanisms controlling crystal size and morphology in skeletal tissues.