INVESTIGATION OF THE EARLY MINERALIZATION ON COLLAGEN IN DENTIN OF RAT INCISORS BY QUANTITATIVE ELECTRON SPECTROSCOPIC DIFFRACTION (ESD)

The earliest crystallites in dentine appear as chains of ''dots'' in u ltra-thin sections viewed by transmission electron microscopy. These d ots rapidly coalesce along the longitudinal directions of the collagen microfibrils to form needle-like structures that coalesce preferentia lly in lateral directions to form ribbon-like or plate-like crystallit es. This morphological interpretation is supported by line-scans of th e corresponding zero-loss filtered electron spectroscopic diffraction patterns, which demonstrate the crystalline structure of the dentine m ineral (apatite). The intensity ratio of the Debye-Scherrer rings of t he characteristic Bragg-reflections (002 to 300, together with 1 or 2 unresolved reflections) shows a maximum in the region of early chain-l ike and needle-like crystallites, decreasing with maturation of the de ntine mineral to the ribbon-plate-like crystallites. Detailed investig ations using line-scans of the zero-loss filtered electron spectroscop ic diffraction patterns through the dentine zone show that the intensi ty ratio found near the mineralisation front is repeated 3-5 times at distances of about 10-20 mu m. This may represent a circadian pattern of mineralisation corresponding to light microscopically visible incre mental lines in dentine.