Endo II PAR 1 Flashcards
(49 cards)
The dental pulp consists primarily of __________ nerve fibers
sensory
Tooth development begins in the ____ week of gestation
5th
Mineralization of primary dentition begins during the _____ week of gestation
14th
When does the permanent dentition begin to develop?
the 14th week of gestation– this is the same time that the primary dentition starts to mineralize
Primary teeth erupt at around _____ months and permanent teeth at around _____ or _____ years
primary– 6 months
permanent– 5 or 6 years
Ectoderm gives rise to what part of teeth?
ectoderm– ameloblasts for enamel
Cranial neural crest gives rise to what part of teeth
cranial neural crest is derived ectomesenchyme– dentin, pulp, periodontal tissue
Over _____ genes have been demonstrated to be active in tooth development
200
Initiation of tooth development begins with the formation of the ________ _________
Dental lamina– thickening of the oral epithelium
The underlying mesenchyme is called the _______ ________ and forms what?
Dental papilla- it forms the future dentin and pulp
3 stages of early tooth development
- Bud stage– mesenchyme condenses and looks like a cap on the dental papilla, multiple signaling molecules involved
- Cap stage– enamel knot is formed in the enamel organ epithelium, critical signaling center
- Bell stage– crown is final shape, histodifferentiation of the cells that will make the hard tissue
2 signals and transcription factors involved in tooth development?
BMP– bone morphologic protein
FGF– fibroblast growth factor
What is the secondary enamel knot responsible for?
Cusp formation in posterior teeth
What are CGRP and SP?
neuropeptides, inflammatory mediators, potent vasodilators
CGRP– calcitonin gene related peptide
SP– substance P
enter the dental papilla in the advanced bell stage (after initiation of dentin and enamel formation)
Pulp dentin complex morphologic zones (picture)
What is in the odontoblastic layer?
- capillaries
- nerve fibers
- dendritic cells
- odontoblasts
What is in the Cell free zone of Weil?
- plexus of Rashkow (rich network of mostly unmyelinated nerve fibers)
- capillaries
- fibroblast processes
What is in the cell rich zone?
- high density of fibroblasts
- undifferentiated mesenchymal cells (stem cells)
- precursors for odontoblast replacement
What is in the pulp proper?
- large blood vessels and nerves– centrally located and branch laterally
- coronal pulp– fibroblasts and collagen in ECM
- apical pulp– dense collagen fibers, continuation of PDL
Dentin components
(dentin is a calcified connective tissue)
70% inorganic material
10% water
20% organic matrix (91% of collagen is type I)
collagenous matrix has phosphoproteins, proteoglycans, acidic glycoproteins, growth factors, and lipids
Dentin tubules are ___um at the DEJ and ____ um at the pulpal surface
DEJ– 1 micrometer
pulpal surface– 3 micrometer
remember that tubules are larger at the pulpal surface than at the DEJ (so there is a **decrease in dentin hardness at the pulp due to increased tubule surface area)
How many tubules penetrate dentin?
millions of tubules– 40,000-70,000 per square mm
Permeability of root dentin is ____ to _____ times LESS than that of coronal dentin
10-20 times less permeable
Etching will ______ the dentin tubules, where as the smear layer (microcrystalline debris) causes dentin tubules to be ________
etching– opens tubules
smear layer– closes tubules
