EX2; Periodontium Development Flashcards
What structures does the periodontium include
cementum
PDL
bony socket
gingiva facing the tooth; junctional and sulcular epithelium
This is the calcified material that covers the root dentin
cementum
This is largely composed to collagen fibers which are embedded on one end to the cementum and the other to the periodontium
PDL
All but which structure serves a role in the attachment of the tooth
sulcular gingiva
True or False
the tooth root develops after the crown
True
What guides root growth
Hertiwig’s epithelial root sheath
The initiation of root dentinogenesis slightly precedes what
periodontal development
What is the inductive signal from HERS for odontoblast differentiation
TGF-β and/or laminin5
Once dentin in the root begins to be laid down, what occurs
HERS separates from root dentin
osteobalsts, cementoblasts, PDL fibroblasts differentiate and migrate to their appropriate locations
What is the order in which the blast cells secrete their substance
cementoblasts and osteoblasts secrete their organic matrix (type 1 collagen) first
PDL fibroblasts secrete their organic collagen matrix
The organic matrices of cementum and bone are secreted before what begins
mineralization
How does the PDL become entrapped in the cementum and bone
it intermingles with the unmineralized matrices and then is locked in during mineralization
All of periodontal development is occurring as what is happening
the tooth is erupting
What changes in orientation does the PDL undergo as the tooth is erupting
starts out in an oblique orientation with the end in the cementum apically, then it becomes more horizontal, then obliquely again with the cementum more coronal
In which direction does the periodontium grow
from the CEJ to the root apex
This type of cementum is mainly acellular and is located on the coronal 2/3 of the tooth
primary cementum
This type of cementum is mainly cellular and located on the apical 2/3
secondary cementum
When is secondary cementum formed
after at least half of the root is completed and about the time the tooth emerges from the oral cavity
Which type of cementum is more important in serving an attachment function
primary cementum
Along the advancing root edge, what is there a continuous layer of
predentin extending between the future DCJ and the pulp
A little coronal to the developing root, the root dentin begins to mineralize, creating what
two separate unmineralized parts of dentin (predentin and non-mineralized dentin at the future DCJ)
At what orientation to the DCJ are the cementum collagen “fiber fringe” laid down
right angles
The cementum fiber fringe extends into what, then what occurs
extends into the unmineralized dentin matrix and upon mineralization the fiber fringe is embedded in the dentin matrix
The firm attachment between the cementum and dentin is a consequence of what
the fact that collagen fibers of these two tissues intermingle prior to mineralization
As primary cementum is laid down, cementoblasts do what
retreat toward the future PDL; they do not become entrapped in the forming matrix (hence, acellular)
Fragmented HERS remain in the PDL as what
epithelial rests of Mallasez
What are the similarities between the formation of primary and secondary cementum
similarity; formed in the same way regarding the fringe and dentin mingling prior to mineralization
difference; cementoblasts become trapped in the cementum matrix (hence, cellular)
Sulcular epithelium arises from what
embryonic oral epithelium
Junctional epithelium arises from what
reduced enamel epithelium
The periodontium structures arise from which portion of the tooth germ
dental follicle
There is a debate over this cell regarding of whether it came from ectomesenhyme (NCC) dental follicle or epithelial; HERS
cementoblasts
What is the general consensus regarding the origin of cementoblasts
cementum-forming cells may be derived from both the dental follicle and HERS
These are secreted growth factors implicated in cementoblast induction
BMPs; bone morphogenetic proteins
These are transcription factors implicated in cementoblast differentiation
RunX
These are extracellular matrix molecules implicated in cementogenesis
bone sialoprotein and osteopontin; both secreted from cementoblast about the same time as the initial collagen matrix; role in mineralization
This is secreted by cementoblasts and plays a role in cementoblast adhesion to root dentin surface and cementum mineralization
bone sialoprotein (BSP)
