Endo II PAR 1 Flashcards
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
Are bacteria usually found in dental tubules when there are caries?
NO– bacteria usually NOT IN DENTIN TUBULES
- most likely due to outward push of dentin fluid and immunoglobulins
Bundles of ________________ collagen reduces the functional diameter of dentinal tubules and thus reduces permeability
Intraluminal collagen
- intraluminal collagen may also trap suspended bacteria
Noxious stimulus causes what protective mechanism
Outward flow– flushing action (reduces bacteria)
- odontoblasts and nerves release inflammatory mediators, vasodilation, and increased plasma fluid into pulp through the dentin tubules
Factors affecting permeability of dentin and removal of substance by the pulp? (picture)
3 theories of dentin sensitivity?
- classic
- modified
- hydrodynamic
Main function of the interstitial fluid?
transport medium for nutrients and waste products between cells and capillary blood– mainly by diffusion through the capillary wall
Argyrophilic Fibers
reticular fibers of the ECM around blood vessels, traverse between odontoblasts into the pre-dentin matrix
most of the fibers in the ECM are type 3 collagen fibers
ECM variation with age and location
older and more apically located = more fibrous
younger and more coronally located = less fibrous
What is the predominant cell of the connective tissue and where does it originate?
Fibroblasts– originate from ectomesenchyme
- responsible for formation and maintenance of the fibrous components and ground substances
What is the major organic component of dental pulp?
Collagen– made and secreted by odontoblasts and fibroblasts
The fibers secreted by odontoblasts eventually become mineralized
Collagen secreted by fibroblasts do NOT mineralize
Type I collagen – product of odontoblasts (process)
- packaged as pro collagen in vesicles
- released as tropocollagen into matrix
- arranges into collagen fibrils extracellularly
Products of odontoblasts? (there are 4)
- Type I collagen
- calcium phosphate transported in vesicles
- enzymes– alkaline phosphatase
- proteoglycans
- mineralization initiation and control
- dentin phosphoprotein (unique to dentin)
What has the highest blood flow of all oral tissues?
Pulp
What passes through the apical foramen?
arterioles, venues, and lymphatics
no collateral circulation!
large vessels move vertically toward coronal pulp and smaller vessels branch laterally
The vessels in the pulp horn form _____ _____ loops
hair pin loops
What connects arterioles directly to venues in the pulp?
AVAs– arteriovenous anastomosis
- these are a way of shunting blood away from an area of injury where damage to micro-circulation may result in thrombosis or hemorrhage
U-turn loops
similar two AVA– plays a role in blood flow regulation during initial stages of inflammation
Sympathetic nerves from the ___________ ___________ __________ have a general vaso_________ effect for the pulp
superior cervical ganglion, vasoconstrictor
Pain from the pulp is transmitted through which fibers?
A delta, C
What is the last major structure to enter the pulp during development?
myelinated A delta fibers
Neuropeptides are produced and released by _________ neurons, and have the _____________ effect of producing an inflammatory response
sensory, antidromal
Substance P is commonly found in ___ fibers
C fibers
Both SP and CGRP are vaso___________s
vasodilators
Which neuropeptides are pro-inflammatory?
Neurokinin A (NKA) and Substance P
Which neuropeptides are anti-inflammatory?
Neuropeptide Y, Vasoactive intestinal peptide (VIP)
