Exam 2 10/16 Intro to Tooth Development Flashcards
Teeth make up ____ of the surface area of the mouth
20% (upper a little more than the lower arch)
Functions of teeth
- mastication
- speech
- esthetics
- weapons of attack and defense
What makes up a tooth?
- enamel
- dentin
- pulp
- periodontium (cementum, periodontal ligament, alveolar bone)
____ is soft connective tissue
Pulp
What is the difference between anatomical and clinical cervix?
Depends on where the gingiva ends - if it ends at the cervical margin, anatomical = clinical cervix. If it ends higher, clinical cervix is longer than the anatomical cervix
When do hard tissues get deposited in the developing teeth?
11-12 weeks
Initial signs of tooth development is at __ weeks
6
How long does tooth development take?
18-25 years (considering wisdom teeth that are the last ones to erupt)
Enamel is derived from:
Oral ectoderm/epithelium
What structures of a tooth are derived from ectomesenchyme?
- dentin
- pulp
- cementum
- periodontal ligament
- portion of alveolar bone
What structures arise from the dental papilla?
Dentin, pulp
What structures arise from the dental follicle/sac?
- cementum
- periodontal ligament
- portion of alveolar bone
The earliest histological indication of tooth development is at:
11 days (thickening of oral epithelium where tooth formation will occur on the oral surface of the first pharyngeal arch)
____ is essential for the initiation of tooth development; maintained by _____
First arch epithelium; cells of dental papilla
What happens to the primary epithelial band?
Thickens as a result of different planes of cell division and grows into the underlying ectomesenchyme - leads to formation of dental lamina and vestibular lamina
As the primary epithelial band thickens, what happens to the surrounding ectomesenchyme?
Condenses around area of dental lamina; tooth bud continues to grow and reshape in relation to the ectomesenchyme condensing around it
Where does the vestibular lamina form in relation to the dental lamina?
Buccal
What eventually happens to the vestibular lamina?
Eventually degenerates so that there is no connection between lip and alveolar process (so vestibules form properly)
When does the primary epithelial band form?
Around 37 days
How many dental laminas form in total?
10 in each arch (20 primary teeth)
Where is the basement membrane found in the tooth bud?
Between ectomesenchyme and oral epithelium (around the round part of the bud)
Where does permanent dentition arise from?
Dental lamina; Permanent molars are an exception, as they are derived from the backgrowth of the primary epithelial band
Stages of tooth development (8)
- Bud
- Cap
- Bell
- Early Crown Dentinogenesis
E. Crown amelogenesis
F. Late crown formation
G. Root formation and eruption
H. Function
____ is always produced before ____ during crown formation
Dentin always produced before enamel
Which stage of tooth development is most complex histologically?
Bell
First epithelial incursion into ectomesenchyme of the jaw occurs during:
Bud stage
What components make up bud?
Dental lamina (poking finger), oral epithelium towards the top
What happens during cap stage?
proliferation of epithelium, ectomesenchyme condensation increases around the cap (enamel organ)
Successional dental lamina can be found beginning at which stage of tooth development?
Cap stage
What components can be found during cap stage?
Enamel organ, Dental Papilla, Dental follicle, cervical loops
Enamel of tooth is derived from:
Enamel organ
Dental papilla forms:
dentin and pulp
Dental follicle forms:
cementum, periodontal ligament, part of alveolus
What cells sit on top of dental papilla
Inner enamel epithelium
Cells on periphery of ectomesenchyme =
outer enamel epithelium
Cervical loops
Where inner and outer enamel epithelium meet (where HERS roots come from)
Where is stratum intermedium found
Along the inner enamel epithelium
Enamel organ is filled with what cells
Stellate reticulum
What do stratum intermedium do
Regulating transport of ions to ameloblasts so they can secrete the enamel
Main change that occurs during Bell stage
Change in shape of crown; completed differentiation of the enamel organ
Dense condensation inside enamel organ:
Enamel knot
When does dental lamina begin to degenerate?
Autolysis after enamel organ is differentiated
Bell stage is marked by:
histodifferentiation and morphodifferentiation
Basement membrane becomes:
DEJ
___ is a potential space
DEJ (caries can spread out here)
If dental lamina cells persist, what happens?
General cell islands may persist, may form small eruption cysts that delay eruption of the tooth
Internal dental epithelium folds, making it possible to:
Recognize shape of future crown pattern
Enamel knot is often continuous with:
Enamel cord or septum
What does enamel knot represent
Organizational center that orchestrates cuspal morphogenesis
As calcification occurs, the dental papilla becomes:
Dental pulp
Tooth bone socket develops around tooth via:
Intramembranous bone formation
Presence of _____ induces lining up and differentiation of ectomesenchyme along the basement membrane and become odontoblasts
Inner enamel epithelium
Formation of dentin marks the onset of:
Crown stage
Mineralization of dentin induces differentiation of internal dental epithelium into:
Ameloblasts (secrete enamel)
Mineralization begins at _____ and proceeds ____
incisal/cuspal tip; coronally (toward cervix)
True or false: odontoblasts secrete mineralized dentin
False - they secrete the organic matrix which mineralizes as an extracellular event
Root formation happens from what part of tooth germ?
Cervical loops
WHat happens during root formation?
Epithelial cells proliferate from cervical loop of enamel organ to form a double layer of cells (HERS)
HERS extends around:
Dental pulp/between it and dental follicle
True or false: HERS completely surrounds dental pulp
False - all but basal portion of pulp –> primary apical foramen
When root sheath is enclosing more of expanding dental pulp, what happens to the ectomesenchymal cells facing the pulp?
Induces them to differentiatiate into odontoblasts and produce dentin of the root
