Exam #3 Flashcards
What structures are Ectoderm?
Enamel Organ, Ameloblast, Enamel, Crown of tooth
What structures are ectomesenchyme?
Everything else
All primary teeth initiate development prenatally between:
6-8 weeks with 10 teeth in each arch
All permanent teeth (succedaneous teeth) develop from the:
successional lamina = bud off primary
Exception: Permanent molars: They develop independently from dental lamina; no successional lamina
What happens in reciprocal signaling mechanisms that are involved in tooth development?
Neural crest cells migrate to the area to form ectomesenchyme. Then Ectoderm of dental arch signals to underlying ectomesenchyme (signals the site of tooth formation), Then ectomesenchyme responds and signals to ectoderm to cause the ectoderm to proliferate
What initiates tooth formation?
Ectoderm: Will form a little thickening
What happens following tooth initiation?
Ectomesenchyme will exhibit differential expression of growth factors and transcription factors throughout dental arch. Ectomesenchyme specifies the pattern via signals to ectoderm directs ectoderm proliferation.
What characteristic events happen in the dental lamina, initiation stage?
DENTAL LAMINA FORMS: Ectoderm proliferates in specific locations to form dental lamina. This demarcates the initial site of tooth formation
When does the vestibule of the mouth develop?
During the Dental lamina, Initiation stage.
Oral ectoderm invaginate on the labial or buccal side of developing tooth and dental arch to form a trough by apoptosis
What characteristic events happen in the Proliferation, Bud stage?
Oral ectoderm continues to proliferate from dental lamina into tooth bud. Ectomesenchyme begins to condense to from a ball recognized as future DENTAL PAPILLA. Continued signaling causes transition of ectoderm tooth bud into cap.
Excessive bud formation may lead to:
Hyperdontia/Supernumerary teeth
T/F: Amount of proliferation of the bud may affect tooth size?
True: Cause marodontia/microdontia
What are the characteristic events of Early Cap stage?
- Proliferation of tooth bud (oral ectoderm)– ENAMEL ORGAN
- Ectomesenchyme condenses beneath tooth bud called DENTAL PAPILLA
- Condensation of ecotmesenchyme surrounding toot bud and papilla is called the DENTAL FOLLICLE
When does the Enamel Knot form?
Late Cap.
Ectoderm proliferates near dental papilla. Formation of enamel knot (oral ectoderm) recognized in the enable organ during late cap stage.
A toot with an Enamel organ, Dental papilla, Dental Follicle would be in what stage?
Early Cap stage
What are the characteristic events of Late Cap stage?
Ectoderm of enamel organ proliferates to form an enamel knot. Primary enamel knot located close to ectomesenchyme of dental papillae. Primary enamel knot is signaling center that causes both enamel organ and dental papilla to differentiate tiny specific cells. Primary enamel knot undergoes apoptosis.
What are the characteristic events of the Early Bell stage?
- Cellular differentiation of enamel organ into 4 layers ( Outer enamel epithelium OEE, Stellate reticulum SR, Stratum intermedium, SI, Inner enamel epithelium IEE), Cerveical loop is visible in enamel organ, Dental papilla starts to differentiate into pre-odontoblasts
What is the Cervical loop?
Point of junction b/w outer epithelium and inner epithelium.
Enamel organ shape of bell with convex and concave border, cervical loop visible, dental papillae located within the concavity of the enamel organ, Dental follicle is visible surrounding the convex surface. What stage?
Early Bell stage
Squamous-cuboidal cell is a key feature of:
The outer enamel epithelium
Vacuolated with desmosomes is a key feature of:
Stellate Reticulum SR
Stratified squamous cells is a key feature of:
Stratum intermedium SI
Tall cuboidal cell closest to BM and region of dental papilla is a key feature of:
Inner enamel epithelium
Characteristic events of Late bell:
Differentiation and cusp formation
- IEE undergoes mitosis and differentiates into Ameloblasts
- Pre-Odontoblasts mature into odontoblasts and start to secrete prevention matrix
- Cervical loop elongates due to growth at cusps
- Dental lamina degenerates- tooth looses connection with oral cavity
- Successional lamina visible lingual to anterior primary teeth
What is the Secondary enamel Knot?
Secondary enamel knots appears at tips of future cusps serves as signaling center in multi-cusped teeth
In what stage do you first see ameloblasts?
Late Bell
What stage is predentin first secreted?
Late bell
First site of mature IEE is located:
At the cusps
Where is the least mature IEE located?
At cervical loop and between cusps
What layer of the Enamel organ will act as stem cells and continue to divide until the crown is completed?
Internal enamel epithelium
What secretes enamel?
Terminally differentiated ameloblasts will secrete enamel. this happens when there is complete maturation of IEE>
What secretes dentin?
Odontoblasts
Where can you find columnar polarized cells with a matrix consisting of ground substance and collagen fibers?
The Odontoblastic process. Can be seen in the late bell stage
Examples of accessory cusps would be:
Cusp of carabelli, Talon’s cups, and dens evaginates
Which tooth is most commonly found missing? Lest?
3rd molars, Maxillary lateral incisors
During what stage would abnormalities most likely affect the tooth shape?
Bell stage
What are the characteristic events of early crown stage?
Shape of tooth established by enamel knot due to signals from ectomesenchyme prior to mineralization
- Primary enamel wont at tip of crown; secondary enamel knots for each cusp
What are the characteristics of End of late bell to Early crown?
Reciprocal signaling between IEE to pre-odontoblast cause terminal differentiation and maturation of each cell.
- Maturation of cells and matrix deposition progresses from cusp to cervical loop.
- Odontoblast-differentiate first -> capable of secreting prevention (ECM proteins)
What is Amelogenesis?
Deposition and mineralization of enamel marks initiation of crown.
What is Dentinogenesis:
Deposition of prevention and mineralization of dentin begins late bell to Crown
When does odontoblast differentiation occur?
- Starts in late bell stage due to inductive signals from IEE and Enamel knot
- Ectomesenchyme of dental papilla differentiates into pre-odontoblast (immature differentiated odontoblasts)
What are the characteristic events of Odontoblast maturation?
- Shape change: cuboidal -> columnar cell
- Polarization: Cell apex and base determined
- A mature odontoblast has an odontoblastic process on apical surface
- ## Function of odontoblast: ECM protein synthesis and secretion
What is the function of odontoblast:
ECM protein synthesis and secretion
What is the first unmineralized dentin matrix deposited first?
Predentin
What are the characteristic events of dentinogenesis?
- Predentin (unmineralized) first deposited in late bell
- Predentin is unmineralized organic matrix located along pulp border adjacent to odontoblasts. Comprised of type I collagen and dental specific proteins
What is the difference between predentin and bone?
Both have type I collagen, Predentin has dental specific proteins
When does Dentin first appear?
Mineralization of prevention to dentin begins during crown stage.
What is the Inductive stage of Ameloblast differentiation?
- Inductive stage: IEE (pre-ameloblast) differentiates into ameloblast. Prior to differentiation IEE (pre-ameloblast) are cuboidal; mitotically active, Induction starts in late bell stage due to signals from enamel knot and prevention matrix
