title: Earliest enamel deposits of the rat incisor examined by electron microscopy, electron diffraction, and electron probe microanalysis.
abstract: In order to describe initial events in enamel mineralization and to help characterize inorganic-organic interactions in this tissue, the earliest rod and interrod enamel in mandibular incisors from normal young adult (100 gm) rats, perfused with 100% ethylene glycol, has been studied by transmission electron microscopy, selected area electron diffraction, and high-spatial-resolution electron probe microanalysis. Diffraction and probe data were correlated precisely from the same extracellular regions of the tissue. Sites were examined progressively as a function of location a) from the most recently deposited enamel adjacent to ameloblasts toward the dentin-enamel junction and b) from the apical portion of the tooth longitudinally toward its incisal end. Electron diffraction patterns consistent with that of a poorly crystalline hydroxyapatite were generated at all locations. Diffraction characteristics changed only slightly toward that of more crystalline hydroxyapatite at different locations. Earliest apical enamel generated molar Ca/P ratios in a range of 0.99-1.46 (average 1.24 +/- 0.15). Molar Ca/P ratios of the first enamel interrod elements increased from approximately 1.24 at ameloblast-enamel boundaries to approximately 1.40 at the dentin-enamel junction, small changes corresponding to those observed in electron diffraction characteristics.
authors.affiliation: Department of Orthopedic Surgery, Harvard Medical School, Children's Hospital, Boston, Massachusetts 02115.
authors.forename: W J
authors.initials: WJ
authors.lastname: Landis
authors.forename: G Y
authors.initials: GY
authors.lastname: Burke
authors.forename: J R
authors.initials: JR
authors.lastname: Neuringer
authors.forename: M C
authors.initials: MC
authors.lastname: Paine
authors.forename: A
authors.initials: A
authors.lastname: Nanci
authors.forename: P
authors.initials: P
authors.lastname: Bai
authors.forename: H
authors.initials: H
authors.lastname: Warshawsky
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D003743:Dental Enamel / Q000032:analysis / Q000648:ultrastructure*; D017886:Durapatite; D004577:Electron Probe Microanalysis; D006882:Hydroxyapatites / Q000032:analysis; D007180:Incisor / Q000032:analysis / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D010758:Phosphorus / Q000032:analysis; D051381:Rats
chemical_list: D006882:Hydroxyapatites; D010758:Phosphorus; D017886:Durapatite; D002118:Calcium