12th Ljudevit Jurak
International Symposium on
June 1-2, 2001
|EFFECT OF THYROXIN ON THE ENAMEL ORGAN OF THE
Medical Academy of Latvia/Riga Stradins University, Departament of
Histology, Riga, Latvia
|The enamel organ performs different functions during tooth morphogenesis:
Acts as a paracrine organ producing epithelium growth factor, nerve
growth factor, and interleukins (Hormia et al., 1998), influences crown
and root development, is responsible for the production of enamel, influences
the formation of the junctional epithelium connecting the gingiva to the
tooth surface (Sawada and Inoue, 1996).
This study aims to elucidate the role of thyroxin in the morphological
changes of the rat molar enamel organ during its morphogenesis.
The hyperthyroid model in this experiment was made according to M.
Kunegava et al. (1980).
The lower first molars were dissected from rat embryos (12 to 18 days
old) and fixed in 10% paraformaldehyde in a 0.1M phosphate buffer (pH 7.4).
Teeth germs were embedded in paraffin. Sections were cut at 8-10 km and
stained by hematoxyllin-eosin, methilen blue, and PAS.
Immersing the material in the same fixative for 3-4 hours, then post-fixing
them in 0.1% osmium tetroxide for 1h performed the fixation for electron
microscopy. Tooth germs were embedded in Epon. Ultrathin sections were
examined using the IEM 7A transmission electron microscope.
We observed that tooth germ dental epithelium and ectomesenchyme in
the control and experimental groups differ in storage of glycogen and secretion
The epithelial cells of the enamel organ, while developing from bud
to bell stages, exhibit differences in proliferation, migration, and apoptosis.
We found differences in the sequences of the formation of different types
of cellular junctions between epithelial cells of the enamel organ. Changes
in the structural and chemical composition of the basal lamina were detected.
We suggest that the epithelial-mesenchymal interactions might be changed.
It will play a crucial role in the events of early tooth morphogenesis.
Hormia M. et al. J. Dent. Res. 1998, 77 (7) :1479
Kunegava M. et al. J. Endocrinology. 1980, 87:431
Sawada T. et al. J. Periodont Res., 1990, 25: 372