Tooth Development with Chu Flashcards
The primitive oral cavity is called? What two plates is it bounded by?
Stomatodeum Bounded by Neural plate and Cardiac plate
The stomatodeum is separated from the foregut (pharynx) by what membrane?
Buccopharyngeal membrane
What structure disintegrates allowing the stomodeum to increase in depth during the development of the face in the 4th week?
Buccopharyngeal membrane
True or False?
The formation of the stomadeum, a shallow depression in ectoderm, initiates the development of the face.
True
What gives rise to oral epithelium ? What does the oral epithelium develop into?
Stomadeum gives rise to oral epithelium, then some of the oral epithelium develops into dental lamina (Stomadeum-> oral epithelium–>dental lamina)
What week does odontogenesis begin? What two tissue types form at the start of odontogenesis?
-6th week -oral epithelium (forms dental lamina) and ectomesenchyme
The appearance of what signifies the start of odontogenesis?
-dental lamina signifies start of odontogenesis
what month do primary teeth begin to form ? When do permanent teeth begin to form?
primary- 4th month permanent-at birth
Generally speaking, what directs and coordinates the process of tooth development?
Genes
Pathways of tooth development involves the interactions of what ?
*Epithelial-mesenchymal interactions* between overlaying oral epithelium and underlying mesenchyme Note: Secretions of growth factors from the dental lamina induce the differentiation of the ectomesenchyme
True or False: Tooth agenesis affects primary teeth more than permanent teeth.
False. Tooth agensis affects permanent dentition more than primary
What is the horse-shoe shaped band of epithelial cells called? (also called the primary epithelial band)
dental lamina *remember, dental lamina arises form oral epithelium, which arises from stomodeum*
what cells surround the dental lamina?
neural crest- derived ectomesenchyme
what two cells structures form the future jaws?
- oral epithelium 2. ectomesenchyme (derived from Neural Crest Cells)
what separates the dental lamina and the ectomesenchyme?
Basal lamina
*so if you are looking at a section of the mandibular process; top layer would be oral epithelium, then basal lamina, then ectomesenchyme
When the primary epithelial band invaginates it is called?
dental lamina
(oral epithelium–>primary epithelial band {invaginates into ectomesenchyme} –> dental lamina)
what is andontia?
what tissues are this defect associated with?
andontia- congenital absence of ALL teeth
associated with ectodermal dysplasia (defect in development of all ectoderm-derived tissues) including dental lamina
what is partial andontia?
hypodontia vs oligodontia?
partial andontia is the absence of SOME teeth, involved with defects of the dental lamina.
- hypodontia- 1-5 teeth missing
- oligodontia- 6 or more teeth missing
hyperdontia?
most common type?
supernumerary teeth of permanent dentition;
caused by extra rooth germ formation–caused by extra invagination of dental lamina into the ectomesenchyme
most common-mesioden (between maxillary central incisors)
tooth formation is initated by factors residing in which arch?
arch 1 oral epithelium
Determinantes in odontogenesis:
Tooth formation is from the combination of __ and __?
neural crest cells and oral epithelium
Overview of Bud Stage (Differentiation of the Dental Lamina)
- incursions of dental lamina
- condensation of ectomesenchymal tissue
What causes the formation of the bud?
invagination/incursion of the dental lamina into the ectomesenchyme
The bud is tethered to the dental lamina by an extension called?
lateral lamina
what condenses around the epithelial bud?
what is the basement membrane?
- ectomesenchyme=condenses around the bud
- basement membrane seperates the bud from the ectomesenchyme
how many discrete outgrowths (placodes) into the ectomesenchyme would you expect to see for deciduous teeth?
where do the first tooth germs form? second? how do they develop from there?
20
first tooth germs= anterior mandible
second=anterior maxilla
then they develop anteriorly to posteriorly in both jaws
what are tooth buds also called?
dental buds, tooth primordia, or tooth germs
what are some abnormalities involved with the bud stage? (2)
define each abnormality.
microdontia- abnormally small teeth
macrodontia- abnormally large teeth
which teeth are most commonly affected by abnormalities?
1st most- 3rd molar
2nd most- maxillary lateral incisors
macrodontia of single teeth is uncommon and often associated with?
hemifacial hypertrophy—-which is unilateral overdevelopment of hard and soft tissues of the face and teeth
overview of the Cap stage
- signifiy by identificaiton of the inner enamel epithelium (IEE), stellate reticulum (SR), and outer enemel epithelium (OEE)
- the IEE, SR, and OEE = enamel organ
- enamel organ is “cap” over the ball of ectomesenchyme
ectomesenchyme forms :
- dental papilla (makes dentin, pulp)
- dental follicle (makes PDL and Cementum)
-enamel knot (cusp development)
Early cap stage:
Epithelial outgrowth called the __ ___ forms a cap over condensed ectomesenchyme?
Enamel Organ
what extends around the rim of the enamel organ and forms the dental follice?
dental papilla (ectomesenchyme ) forms the dental follice
what three things combine to form the tooth germ?
enamel organ
dental papilla
dental follice
the enamel organ is ___ in origin?
What is the significance of the enamel organ during the cap and bell stages?
enamel organ is epithelial in origin
gives rise to distinct cell layers
Note: teeth develop from two types of cells:
oral ectoderm-forms the enamel organ
mesenchymal cells-from the dental papilla
Name the distinct cell layers of the enamel organ, and their significance
(from outer most to innermost )
- outer enamel epithelium=covers enamel organ
- stellate reticulum= produces proteoglycans to maintain morphology of enamel organ
- stellate intermedium=assists ameloblasts in formation of enamel, also initiates formation of dentin from dental papilla cells
- inner emamel epithelium=becomes ameloblasts, which form enamel
- cervical loop (OEE+IEE)= will become cervic of future tooth
define dental papilla, located next to?
what does the dental papilla form? (2 major things)
peripheral cells form? inner cells form?
dental papilla- condensation of ectomesenchymal cells, located next to the enamel organ, but separated by a basement membrane
2 main things-forms odontoblast and pulp
- peripheral most cells bordering basement membrane responsible for dentinogenesis, form odontoblasts, which secrete dentin
- inner most cells of dental papilla form pulp
the peripheral cells of the Dental papilla differentiate into?
odontoblasts, secrete dentin
*peripheral cells of dental papilla responsible for dentinogenesis, forming of odontoblasts–>dentin
the inner cells of the dental papilla form?
pulp!
What is the dental sac/follicle?
ectomesenchymal cells surrounding the emamel organ and the dental papilla
The dental follicle strucuture is cellular and fibrous than the dental papilla.
dental follicle is LESS cellular and MORE fibrous than dental papilla
The inner cells of the dental follicle become what?
cementocytes, produce cementum
The outer cells of the dental follice form? what do the outer cells contribute to?
outer cells become periodontal ligament (PDL)
contribute to alveolar bone formation
True or False:
Permanent teeth form on the lingual aspect of the deciduous tooth germ.
True
What is Dens in Dente?
“tooth within a tooth”, the enamel organ expands more than normal and invaginates into the dental papilla.
What is Fusion?
Does Fusion result in more or less teeth than normal?
fusion- joining of two separate adjacent tooth germs into one tooth with common formation of dentin.
results in LESS number of teeth than normal, have extra-wide crown with one pulp cavity.
What is Gemination? Would you have more or less teeth than normal?
One tooth germ attempting to divide into two, resulting in two wide crowns that are imcomplete.
-would have correct number of teeth
Overview of the Bell Stage
- differentiation of enamel organ (Cervical loop, IEE, OEE, SI, SR, Enamel knot)
- fragmentation of dental lamina (epithelial pearls, rests of serres)
- Role of IEE in cusp formation
Early Bell stage:
Name and define the two types of differentiation
Histodifferentiation- ameloblasts and odontoblasts acquire their phenotype
Morphodifferentiation- enamel organ takes on shape incisor, canine, or molar
what is the center of the enamel organ called? Describe the shape.
Stellate Reticulum, star shaped.
What are the functions of the Stellate Reticulum?
Stellate reticulum cells create glycosaminoglycans (GAGs), which cause water to be drawn into the cells and increases size of the enamel organ
-transports nutrients and calcium from blood vessels to ameloblasts (form enamel)
*Note: SR cells maintain contact by desmosomes (type of cell junction) which creates their star shape
Stratum Intermedium (SI) function?
transports phosphate from blood vessels into the enamel organ
*note: the stratum intermedium has high alkaline phosphate activity due to the transporting of phosphate
Which two layers of the enamel organ work together to form enamel?
Stratum Intermedium - transports phosphate from blood vessels to enamel organ
Inner Enamel Epithelium - forms ameloblasts, which produce enamel
Inner Enamel Epithelium:
- differentiates into?
- has a high concentration of?
- ameloblasts, which secrete enamel
- high concentration of glycogen
The basal lamina between the IEE and dental papilla becomes?
the DEJ, dentoenamel junction
Outer Enamel Epithelium:
Forms what part of enamel organ?
At the end of the bell stage, OEE become occupied by?
OEE - forms outer periphery of enamel organ,
at end of bell- becomes occupied by blood vessels from dental papilla
Cervical Loop Region:
This is where the ___ and ___ meet?
How does the enamel organ change shape in this region?
IEE and OEE meet at cervical loop, this meeting forms Hertwig’s Epithelial Root Sheath
-enamel organ elongates, and resembles a bell
the joining of the IEE and OEE in the cervical loop region is called _________?
Hertwig’s Epithelial Root Sheath (HERs)
What is Hertwig’s Epithelial Root Sheath, and what does it initiate?
-double layer epithelial root sheath, created by fusing of IEE and OEE
function of HERs:
- root formation after crown is formed
- HERs signals odontoblasts of the dental papilla to differentiate
at the ___ ___ , enamel joins the cementum.
cervical loop, will become the CEJ
What are the two important events that occur during the bell stage?
- dental lamina (lateral lamina) disintegrates (not completely)
- crown pattern and number of cusps of the tooth is established by the folding of the IEE (morphodifferentiation)
During the bell stage, part of the Dental lamina disintegrates, separating the developing tooth from?
the oral epithelium
Note: Before a tooth an function, it must reestablish a connection to the oral epithelium via juntional epithelium
Which part of the dental lamina does not disintegrate, and what does it give rise to?
posterior part of dental lamina does not disintegrate, give rise to 12 buds, which will become permanent molars
During the bell stage, morphodifferentiation (crown pattern and number of cusps forming) is completed by?
Folding of the IEE
the folding is caused by mitotic divisions within the IEE (not because of pressures w/i dental papilla )
What are epithelial pearls? What is the other name for epithelial pearls?
fragmentations of dental lamina that do not degenerate, causing clusters of epithelial cells surrounded by connective tissue.
Also called Rests of Serres
What can Epithelial Pearls (Rests of Serres) give rise to?
Eruption cysts, which become blue or purple/brown, they can delay normal tooth eruption
odontomes, tumors
When the IEE cells first differentiate this represents the site of future?
cusp development
The Outer cells of the dental papilla give rise to?
Dentin
The inner cells of the dental papilla give rise to?
pulp
Inner cells of the dental follicle give rise to?
Cementum
Outer cells of the dental follicle give rise to?
PDL and Alveolus
All tooth structures EXCEPT ___ are derived from neural crest cells.
enamel, ectodermal in origin
all other structures are from neural crest cells (mesenchyme)
what type of cell in the dental papilla adjacent to the IEE differentiates into odontoblasts?
Mesenchymal cell
