Odontogenesis

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Odontogenesis
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What is this?
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Bud Stage

• Human, frontal section (10th week).

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What are the Black Arrows in this picture?
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The arrows are showing that there has been a down
growth of the oral epithelium into the underlying
mesenchyme
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This light micrograph shows the bud stage of
tooth development. Note that there has been a
down growth of the oral epithelium (e) into the
underlying mesenchyme (m), and the epithelium is
separated from the connective tissue by a
distinct basement membrane. Inferior to the
epithelial bud there appears to be the begining
"condensation" of mesenchymal cells (arrow),
which will eventual become the dental papilla and
the dental follicle. None of the distinctive
characteristics of the dental organ (cap stage)
have yet appeared, i.e. there is no recognizable
inner and outer dental epithelia.
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What is this?
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Meckel's cartilage
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What is this?
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Nasal Septum
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What stage is this?
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Toothbud, late cap stage
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1 outer enamel (dental) epithelium
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2 enamel knot
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3Stellate reticulum
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4 dental papilla
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5inner enamel (dental) epithelium
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6 dental follicle
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What stage is this?
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Bell stage
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1 Stellate reticulum
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2 succedaneous toothbud 
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3 inner enamel epithelium
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4 enamel (dental) epithelium
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5 dental papilla
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6 Cervical loop
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7dental follicle
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Enamel
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Enamel LamellaeImage 06 

• The enamel lamellae appear as longitudinal cracks
  in the enamel (some are cracks) that sometimes
  extend into the dentin.

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Enamel TuftsImage 07

• Several enamel tufts, which appear as wavy groups
  of enamel rods, extend from the dentinoenamel
  junction into enamel to about one quarter of its
  thickness. Unstained, 100x

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Enamel SpindlesImage 09

• The enamel spindles appear as short, straight,
  thin, dark structures which extend for only short
  distances into enamel. They are residual tubules
  formed when odontoblastic processes extend across
  the dentinoenamel junction during odontogenesis.
  In ground sections, the odontoblastic processes
  disintegrate and are replaced by air which
  appears dark in transmitted light. Unstained, 100x

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Gnarled EnamelImage 12

• Bundles of enamel rods appear to intertwine in a
  highly irregular manner in the cusp region of
  teeth to form gnarled enamel. The phenomenon of
  gnarled enamel appears to be an optical illusion.
  Unstained, 40x

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Hunter-Schreger BandsImage 14

• Hunter-Schreger bands appear as alternating light
  and dark bands in light microscopy. They are best
  observed in polarized or reflected light. What is
  the underlying basis for the appearance of this
  phenomenon? Unstained, 40x

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Dentin
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dentinoenamel junction
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Lines of Retzius in enamel
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Contour lines of Owen in dentin
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Dentinal TubulesImage 25
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Lines of von EbnerImage 36

• The lines of von Ebner are oriented in the
  horizontal axis at approximately right angles to
  the dentinal tubules which run in the vertical
  axis. Unstained, 40x

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Interglobular DentinImage 41Ground Section

• The regions of interglobular dentin appear as
  black spaces which are located in the crown of
  the tooth near the dentinoenamel junction. Notice
  that the dentinal tubules traverse the
  interglobular dentin. How is interglobular dentin
  formed? (Higher magnification of image 40)
  Unstained, 200x

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Enlarged region of the above photo
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Tomes' Granular LayerImage 42

• Tomes' granular layer appears as a black layer of
  granular structures which are located in the
  peripheral zone of root dentin adjacent to the
  cementum. Unstained, 100x

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What is 1?
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1Crestal interdental ligments
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What is 2?
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2 horizontal interdental ligments
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What is 3?
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3 Oblique interdental ligments
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What is 4?
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4 apical interdental ligments
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Transseptal FibersImage 14

• Transeptal and horizontal fibers

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Epithelial Rests of MalassezImage 25

• The epithelial rests appear as small clusters of
  epithelial cells which are located in the
  periodontal ligament adjacent to the surface of
  cementum. They are cellular residues of the
  embryonic structure known as Hertwig's epithelial
  root sheath. Observe the epithelial rests,
  cementoblasts and the layer of acellular
  cementum. Although the normal function of
  epithelial rests is unknown, they can develop
  into pathological dental cysts.

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Junctional Epithelium

• This is a of the
• junctional epithelium (je),
• the enamel (e),
• dentin (d)
• and cementum (c).
• You can also see fibers of the dentogingival
  ligament (black arrows). The white arrows show
  Sharpey's fibers inserting into the cementum.
  Junctional epithelium is originally derived from
  reduced enamel epithelium, and the epithelium
  cells facing the enamel (or dentin or cementum)
  are 'attached' to the hard surface via a modified
  basement membrane. Interestingly, if the
  junctional epithelium is removed surgically, it
  will reform, even against an implant surface.

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What is this?
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TMJ
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1Condyle
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2 Lateral Pterygoid Muscle
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3 Articular disc
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