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.

Biophysical Analyses of Sequential Bands of Enamel Related to Ruffle-ended and Smooth-ended Maturation Ameloblasts

“…Nevertheless, these surface analysis volumes represent enamel capable (or incapable, as the case may be) of being stained with GBHA and other dyes (McKee and Warshawsky, 1989), and consequently might have shown differences. The XRD, IR, XPS, and WDS analyses of both enamel strips gave spectra, electron binding energies, and Ca/P molar and intensity ratios consistent with those previously published for enamel (Landis and Navarro, 1983;Landis et al, 1982Landis et al, , 1988Debari et al, 1986;Sasaki et al, 1987). XRD indicated that the enamel examined was hydroxyapatite, and the other three techniques, while not definitive, supported this conclusion.…”

“…In the continuously erupting incisor of the rat, enamel formation consists of spatially and temporally distinct developmental stages that lead to the formation of the highly crystalline apatite of tooth enamel. The various stages of amelogenesis in the rat have been well-characterized both morphologically and functionally with respect to cellular activity in the enamel organ (Warshawsky and Smith, 1974;Warshawsky, 1985) and with respect to the major organic (Robinson and Kirkham, 1985) and inorganic (Landis et al, 1988) components of the enamel. In particular, during the maturation stage of amelogenesis, where a large percentage of organic material is lost from the enamel (Glimcher et al, 1977;Robinson et al, 1977;Robinson and Kirkham, 1985), together with a massive influx of calcium and phosphorus (Robinson et al, 1974(Robinson et al, , 1981Hiller et al, 1975;Suga, 1982), there is a banded distribution of two different ameloblast morphologies in the enamel organ (Takano and Ozawa, 1980;Reith and Boyde, 1981a;Warshawsky, 1985;Nanci et al, 1987;Smith et al, 1987).…”

Tubule formation and elemental detection in developing opossum enamel

“…These reflections are characteristic of a poorly crystalline hydroxyapatite as the principal mineral phase of the tissue. matrix, for example, in Landis et al (1988) where CalP text that the regions of enamel may have sampling molar ratios in early interprismatic rat enamel ranged differences (see Table l ) , that calcium transport to the from 1.24 at the cell-enamel boundary to 1.40 at the mineralizing matrix may be a very complex process dentin-enamel junction. The results found in the (Bawden et al, 1982;Crenshaw and Takano, 1982; present study may possibly be understood in the con -Bawden, 19891, or that carbonate presence may influ- ence the Ca/P ratios.…”

Initial aspects of mineralization at the dentino-enamel junction in embryonic mouse incisor in vivo and in vitro: A tem comparative study

“…Stippled material diffuses into the dentinal matrix (Nanci et al, 1994). Mineral deposits in the enamel matrix occur only in front of a distinct layer of mineralized dentine (Kallenbach, 1971;Landis et al, 1988). This morphological sequence is now well established (Diekwisch et al, 1995).…”