HERE:

Do dentists sutdy this kind of thing? ACTUALLY .... yes.

Joel

http://www.cwru.edu/dental/web/histologyoral/imageinfo/teeth/bellstageoverview.h
tm#bellstage04

Good photomicrographs!

The ticket to understanding this is the word, "LAMINA." This is like
the words "laminated countertops, i.e. Formica." It means a layer.

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Tooth Germ, Bell Stage
H&E stain. Magnification 30X.

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With continuing proliferation and differentiation of the tooth germ,
the enamel organ assumes the shape of a bell which envelops the dental
papilla. A new layer of cells termed the stratum intermedium appears
between the inner enamel epithelium and the stellate reticulum. A
dental lamina connects the outer enamel epithelium of the enamel organ
to the oral epithelium. The distal end of the proliferating dental
lamina forms the anlage of the permanent tooth, the so-called
successional lamina. The third component of the tooth germ is the
dental sac which is a concentration of mesenchymal connective tissue
that encircles the enamel organ and the dental papilla.  

Tooth Germ, Bell Stage
H&E stain. Magnification 40X.

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Higher magnification of previous slide. Notice that an invasion of
mesenchymal tissue coincides with the disruption of the dental lamina.


Tooth Germ, Bell Stage
H&E stain. Magnification 200X.

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Higher magnification of previous slide. Epithelial pearl formations
are evident in the regressing dental lamina.


Tooth Germ, Bell Stage
H&E stain. Magnification 40X.

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Identify the three parts of the tooth germ and the four layers of the
enamel organ.


Tooth Germ, Bell Stage
H&E stain. Magnification 200X.

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Higher magnification of previous slide. The layer of low columnar
cells of the inner enamel epithelium is continuous with the layer of
cuboidal cells that form the outer enamel epithelium at the structure
termed the cervical loop.


Tooth Germ, Bell Stage
H&E stain. Magnification 200X.

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Higher magnification of previous slide (two slides up). Scanning from
left to right, identify the dental sac, outer enamel epithelium,
stellate reticulum, stratum intermedium, inner enamel epithelium and
the dental papilla.




Tooth Germ, Bell Stage
H&E stain. Magnification 200x.

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Higher magnification of previous slide (three slides up). The layers
of the tooth germ are shown as they appear at the top of the bell.


Tooth Germ, Bell Stage
H&E stain. Magnification 400x.

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Higher magnification of previous slide (four slides up). Identify the
star-shaped cells of the stellate reticulum, the flat cells of the
stratum intermedium, the tall columnar cells of the inner enamel
epithelium and the dental papilla.


Tooth Germ, Bell Stage
H&E stain. Magnification 400x.

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Higher magnification of previous slide (five slides up). The dental
sac which is supplied with blood vessels is positioned on one side of
the outer enamel epithelium and the mucoid-filled stellate reticulum
is on the opposite side.




ATooth Germ, Bell Stage
H&E stain. Magnification 40x.

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Identify the histologic features of the tooth germ that you have
studied in previous frames. Two additional structures to identify are
the lateral dental lamina which extends from the dental lamina proper
to the top of the bell and the enamel niche which is presumably formed
by the migration of mesenchyme into the dental lamina.


Tooth Germ, Bell Stage
H&E stain. Magnification 100X.

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Higher magnification of previous slide. The permanent tooth bud
(successional lamina) is formed by the proliferation of the dental
lamina toward the lingual or palatal side of the deciduous tooth germ.




Tooth Germ, Bell Stage
H&E stain. Magnification 200X

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Higher magnification of previous slide.


Maxillary Incisor Tooth Germ, Bell Stage
Mallory's trichrome stain. Magnification 30X.

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Review the histologic features of the tooth germ and its associated
structures. Notice that an incisive canal is located on the left and
the upper lip on the right side of the photomicrograph, respectively.




Maxillary Incisor Tooth Germ, Bell Stage
H&E stain. Magnification 100X.

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Higher magnification of previous slide. A linear group of cells
collectively termed the enamel cord traverses the stellate reticulum.
It is a transient structure with no known function.