Initial aspects of mineralization at the dentino-enamel junction in embryonic mouse incisor in vivo and in vitro: a tem comparative study.
The frontier between the enamel organ and the dental papilla, the future dentino-enamel junction, undergoes coordinated modifications. The mineralization of the extracellular matrix starts within the predentine, which is a prerequisite for the formation of the first enamel crystallites in vivo. We investigated the dentino-enamel junction using the embryonic mouse incisor as a model. Our data showed that the notion of the dentino-enamel junction should not be restricted to the thin interface classically described. A temporo-spatial survey from the epithelio-mesenchymal junction to the dentino-enamel junction delineated a clear sequence of events characterized by the early deposition of electron-dense granules, followed by the appearance of patches of stippled material at the dentino-enamel junction. The first tiny enamel crystallites appeared in the vicinity of this material which presented a well-ordered alignment. The comparison of data obtained in vivo on 17-, 18-, 19-d-old embryonic incisors with those obtained in vitro using 15-d-old embryonic incisors cultured for 7 d emphasizes the relevance of this sequence. Helicoidal growing crystals were observed in cultured tooth germs but never in vivo.
Meyer
J M
JM
INSERM U 424 Faculté de Médecine, Strasbourg, France.
Bodier-Houllé
P
P
Cuisinier
F J
FJ
Lesot
H
H
Ruch
J V
JV
D000566:Amelogenesis; D000818:Animals; D003743:Dental Enamel / Q000196:embryology / Q000648:ultrastructure*; D003804:Dentin / Q000196:embryology / Q000648:ultrastructure*; D003810:Dentinogenesis; D007180:Incisor / Q000196:embryology / Q000648:ultrastructure*; D051379:Mice; D008854:Microscopy, Electron