Oral Histology Final

Front 1

What is odontogenesis first initiated by? What later takes it over?

Back 1

Factors in first arch oral epithelium that act on underlying mesenchyme.

Ectomesenchyme later take sit over.

Front 2

What is essential for the initation of tooth development? What is it maintained by?

Back 2

First arch oral epithelium - maintained by cells of dental papilla

Front 3

When is the first sign of human tooth development?

Back 3

6th week of embryonic life.

Front 4

What does the oral epithelium look like before tooth formation? Then what is formed?

Back 4

Basal layer of high cells, surface layer of flattened cells. Epithelium is separated from connective tissue by basement membrane.

Then, primary epithelium band is formed - formed from the basal layer proliferating faster than other layers.

Primary epithelial band -> dental lamina and vestibular lamina

Front 5

Primary epithelial band:

1) When does it form?
2) What is it?
3) What arises from it?

Back 5

1) 37 days
2) Continuous band of thickened epithelium that corresponds to future site of upper and lower dental arches
3) Dental lamina and vestibular lamina

Front 6

Dental lamina:

1) What is it responsible for?
2) How is it formed?
3) What do permanent incisors, canines, and premolars form from?
4) What do molars form from?
5) When is the initiation of the permanent central incisor?
6) When is the initiation of the second premolar?
7) Initiation time for first permanent molar?
8) Initiation time of second permanent molar?
9) Initiation time of third permanent molar?

Back 6

1) Intiation of deciduous and permanent teeth.

2) Continuous/localized proliferation, epithelial ingrowths into ectomesenchyme. Part of ingrowth is achieved by ectomesenchyme upgrowth.

3) Lingual to enamel organ of deciduous teeth, and as outgrowth of dental lamina of the primary teeth

4) Molars have no primary precursor; derived from backgrowth of the primary epithelial band

5) 5 months in utero

6) 10 months

7) 4 months

8) 1st year

9) 4-5 year

Front 7

What does the vestibule form from? Describe the process.

Back 7

Proliferation of vestibular lamina in ectomesenchyme. Cells enlarge and then degenerate to form a cleft that becomes the vestibule between cheeks and tooth-bearing areas.

Front 8

What are the 5 stages of tooth development?

Back 8

1) Bud (initiation)
2) Cap
3) Bell (histo/morphodifferentiation)
4) Crown (apposition)
5) Eruption (root formation)

Front 9

Bud stage:

1) What happens?
2) Shape of epithelial cells?
3) What's packed around the bud?
4) What are the three parts of a tooth bud, what are they derived from, and what do these derivations produce?

Back 9

1) First epithelial excursion into surrounding ectomesenchyme of the jaw
2) Cells show little change in shape/function
3) Supporting ectomesenchyme packed around bud, separated from epithelium by the epithelium's basement membrane
4) Enamel organ - oral ectoderm - enamel.
Dental papilla - head ectomesenchyme from neural crest - pupl and dentin
Dental sac - head ectomesenchyme from neural crest- cementum, PDL, part of alveolar bone

Front 10

Meckel's cartilage:

1) What is it?
2) What does it turn into?
3) What is its role in the formation of the mandible?

Back 10

1) Cartilage of the first arch
2) Sphenomandibular ligament and two ear ossicles
3) Serves as a GUIDE for the mandible, doesn't contribute to the mandible at all.

Front 11

Cap stage:

1) What happens?
2) What does the epithelium resemble?
3) What germ layer is each structure derived from?
4) What are the new developments in the cap stage?

Back 11

1) Epithelium continues to proliferate, ectomesenchyme density increases adjacent to epithelial ingrowth.
2) Cap (enamel organ) sitting on a ball of cells (dental papillae) with additional ectomesenchyme condensation (dental follicle) around the whole thing.
3) Dental organ - ectoderm, forms enamel of the tooth.

Dental papilla - ectomesenchyme - forms pulp and dentin.

Dental follicle (sac) - forms cementum, PDL, part of alveolus.

4) Inner and outer epithelia - OEE is at convexity, single row of cuboidal cells. IEE is at concavity, layer of tall cells.

Stellate reticulum - cells in middle of enamel organ, separate by increase in intercellular fluid. Branched reticular form, spaces between are filled with mucoid, cushiony consistency, later support enamel forming cell.

Enamel knot - cells in center of stellate reticulum pack closely, vertical extension = enamel cord. Temporary and disappear before enamel begins to form.

Front 12

How much of the mouth does the tooth make up?

What are its functions?

What are the four main components?

Back 12

20% of surface area; upper 24 cm^2, lower 20 cm^2

Mastication, speech, aesthetics, weapons of attack and defense

Enamel, dentin, pulp, periodontum (cementum, PDL, alveolar bone)

Front 13

Bell stage:

1) What two differentiations happen during the bell stage?

2) What processes happen during this stage?

2a) What happens if cell islands persist?

3) What are the four distinct cell layers at this stage?

4) What is the borderline between the IEE and dental papilla called?

5) What is the name of where the inner and outer enamel epithelium meet?

6) How does the dental papilla relate to the dental organ at this point?

7) What happens to the outer enamel epithelium?

8) What happens to the stellate reticulum? How is the stellate reticulum connective to each other/OEE and stratum intermedium?

9) Stratum intermedium: makeup/what does it do?

10) IEE - what is it dervied from? Shape? What do these cells differentiate into and when?

Back 13

1) Histodifferentiation (cells that will be making hard tissues of the crown, ameloblasts and odontoblasts, acquire distinctive phenotype), morphodifferentiation (crown assumes final shape)

2) Dental lamina breaks up, separating developing tooth from oral epithelium. IEE folds, making shape of future tooth. Tooth continues development separately from oral epithelium.

3) Outer enamel epithelium, stellate reticulum, stratum intermedium, inner enamel epithelium

2a) Form small eruption cysts that delay eruption of the tooth

4) Future dentinoenamel junction.

5) Cervical loop.

6) Still separated by a basement membrane. (Acellular zone)

7) Cells become irregular, can't be distinguished from stellate reticulum. Capillaries in connective tissue proliferate, invade stellate reticulum, supply IEE.

8) Expands further (more fluid), cushion against any physical forces that might distort shape of developing dentinoenamel junction. Desmosomes.

9) 1-3 layers of flat/cuboidal cells between stellate ret. and IEE. Either controls fluid diffusion/produce enzymes needed to produce enamel.

10) Basal layer of oral epithelium. Low columnar, diameter 4.5 micra. Hexagonal. Ameloblasts - earlier in incisal/occlusal area than in area of cervical loop.

Front 14

Vascular supply:

1) Where are clusters of blood vessels found?
2) Is the dental organ vascular or avascular? How does it get its nutrition?
3) When do nerve fibers begin developing? What is the target? When is the innervation of dental papilla evident?
4) When do nerve fibers enter the dental organ?

Back 14

1) Around the tooth germ and in the dental follicle, entering the dental papilla
2) Since it's an epithelial derivative, it's avascular. Gets it supply by diffusion of blood supply from dental follicle.
3) Begin developing in late bud-early cap stage. Target is dental follicle. Innervation of dental papilla not evident until dentinogensis.
4) Nerve fibers NEVER enter the dental organ.

Front 15

Enamel knot:

1) What is it?
2) What is it continuous with?
3) Why is the enamel knot important?

Back 15

1) Thickening in internal dental epithelium in the center of the tooth germ
2) Enamel cord or septum - strand of cells running from knot to outer enamel epithelium
3) Determines the crown pattern of the tooth