1what is dental lamina
ectoderm derived from epithelium
26th week of embryonic life
dental lamina invaginates into adjacent ectomesenchyme
33 stages of tooth development
bud, cap, bell
4tooth bud parts
enamel organ
dental papilla
dental follicle (sac)
5enamel organ composed of
ectodermal cells, which birth ameloblasts, which make enamel
6dental papilla composed of
ectoMESENCHYmal cells, birth odontoblasts, which make dentin
7dental follicle (sac) composed of
ectomesenchymal cells, birth PDL
8PDL cells
cementoblasts - cementum
osteoblasts - alv bone proper (bundle bone)
fibroblasts - sharpeys fibers (principal fibers)
9bell stage: differentiation of cells
inner enamel epithelium (IEE) cells into ameloblasts
[IEE induce differentiation of dental papilla outer layer to odontoblasts]
ectomesenchymal of dental papilla to odontoblasts
[odontoblast secrete dentin, stimulating enamel secretion from ameloblasts]
10what forms hertwig's epithelial root sheath
IEE and OEE fuse
11HERS determines
size and shape of root(s)
12what happens to HERS when dentin mineralizes
fragmentation, EMC stem cells from dental follicle contacts dentin and differentiate into cementoblasts
13what are epithelial rests of malassez
remnants of HERS fragments in PDL; cluster of epithelial cells surrounded by basement membrane
14epithelial rests of malassez are involved in
formation of radicular cysts during chronic inflammation
15how are lateral/accessory canals formed
breaks in HERS prior to dentin formation
16lateral or accessory canals can
potentially serve as passageways for bacteria between tooth and periodontium
17lateral or accessory canals are most common in
apical third of root
18why is the apical foramen usually not at the true apex of the root
cementum deposition continues thru life, as more laid down the foramen is further pushed away from the true apex
19size and shape of apical foramen
0.3-0.6mm funnel shape
20when does HERS formation stops
when apical foramen is created
21apical foramen
main opening of the root canal system; major apical diameter
usually .5mm away from radiographic apex of tooth
22apical constriction
minor apical diameter; narrowest portion of canal, usually .5mm away from AF
23CDJ (cementodentinal junction)
histological locatio where cementum on outside of root meets dentin within the canal
24why do we use the apical constriction as a reference point
CDJ is not detectable clinically
25what is the EWL (estimated working length)
1mm away from the radiographic apex (RA-1mm)
26functions of the pulp
**most impt** formation of dentin by odontoblasts
induce enamel formation (from its dentin prod)
supply nutrients
immune defense; macrophages, dendritic cells, lymphocytes
response to stimuli; A-delta and C-fiber
27dentin composition
70% inorganic (calcium hydroxyapatite)
20% organic (t1 colla)
10% h2o
28primary dentin produced when?
during tooth development until eruption
29what dentin constitutes a major part
primary dentin
30primary dentin structure
regular and tubular
31secondary dentin produced when?
after tooth erupts, continue thru life
32secondary dentin structure
less regular, laid down slower
33in order to protect itself from pathologic processes, what does the pulp do
make tertiary dentin
34tertiary dentin function
protect pulp from noxious stimuli and injury
35tertiary dentin structure
irregular, less tubular or atubular
36types of tertiary dentin
reactionary
reparative
37what makes reactionary dentin
original odontoblasts
38what makes reparative dentin
replacement odontoblasts (odontoblast like cells)
39what does it mean if pulp chambers/canals are calcified
xs 2ndary or tertiary dentin
40dentin layers
mantle, circumpulpal, predentin
41mantle dentin
1st layer of primary dentin formed
adjacent to enamel; slightly less mineralized
42circumpulpal dentin
major part of primary/secondary dentin
formed after mantle dentin
43predentin
unmineralized organic matrix; between odontoblasts and circumpulpal
44dentinal tubules location
entire length of dentin from DEJ to pulp
45permeability of dentinal tubules
inc permeability closer to pulp from wider, concentrated dentinal tubules
46dentinal tubules shape
inverted cone; tapered so widest pulp and narrowest DEJ
47which location has more tubules
pulp; why it is more permeable
48intertubular dentin
between tubules; give tensile strength
49intrAtubular dentin
lines inner walls of tubules
less collagen fibers and more mineralized, so harder than intEr
50which dentin is more quickly dissolved by acid etch
intrAtubular dentin; why tubules are opened during acid etch
51earliest response of dentin to caries
dentinal sclerosis
52what is dentinal sclerosis
partial or complete blockage of dentinal tubules from noxious stimuli or aging
53dentinal fluid
ultrafiltrate of blood from pulpal capillaries
54outermost layer of pulp (odontoblast layer)
odontoblastic processes embedded in tubules, extend into dentin
more odontoblasts in coronal than radicular pulp
55cell-free zone (Weil)
relatively free of cells
contain capillary plexus and plexus of rashkow (sensory)
56cell rich zone
fibroblasts, immune cells, undifferentiated mesenchymal stem cells
odontoblast-like cells from this layer migrate, replacing injured odontoblasts
more in coronal than radicular pulp
57pulp proper
central mass of pulp; loose CT, larger BV and nerves
58most common cell type in pulp proper
fibroblast
59odontoblasts synthesize
mainly type 1 collagen
60odontoblasts reproduction
they are post-mitotic, do NOT undergo cell division
61most common cell in pulp
fibroblasts
62fibroblasts synthesize
type 1, 3 collagen, proteoglycans/GAGs (ground subs)
63most prominent immune cell in pulp
dendritic cell (8%)
64macrophage role in pulp
phagocytosis and APCs
65what is only present in injured pulp
mast cell
66immune cells in pulp
dendritic cells, macrophages, t lymphocytes, mast cells
67pulp collagen types
1 and 3; 1 prominent
68glycosaminoglycans (GAGs) link to
prots and saccharides to form proteoglycans
69what do proteoglycans do
hydrophilic molecules that bind with water, makes gel
70pulp vasculature
NO ARTIERIES OR VEINS; only arterioles, capillaries, venules, lymph vessels
anastomoses is shunting system for injury and repair
71young pulps vasculature
highly vascular
72coronal vs radicular vasculature
coronal vascular supply 2x of radicular
73what arteries supply blood to tooth
inf alveolar art, posterior superior alveolar art, infraorbital art
74extensive branching of arterioles occur where, forming what
cell free layer, form sub-odontoblastic terminal capillary network/plexus
75venules of teeth drain to
maxillary vein (post) or facial vein (ant)
76lymphatics help decrease
interstitial fluid pressure
77what regulates blood flow for healthy pulp
sympathetic autonomic regulation (controls vasomotor tone); NE > vasoconst
78what regulates blood flow for inflamed pulp
neuronal; neurogenic inflammation
79inflamed pulpap sensory neurons release
neuropeptides (SP, CGRP); they are pro inflam mediators
80neuropeptides cause
vasodil, inc vasc permeability
81vascular changes during inflammation
vessels vasodil
inc vasc permeability
inc interstitial tissue fluid/prots
82what kind of enviro is pulp
non-compliant; does not inc vol to accomodate inc tissue fluid/pressure since it is encased in rigid dentin
83self strangulation theory
inc in tissue pressure > strangulation of vessels and necrosis but THIS IS NO LONGER TRUE
84what happens instead of self strangulation theory
capillaries localize blood to specific area of injury, localizing tissue fluid pressure to that area
85how is pulpal tissue fluid pressure maintained to normal near injury
inc intraluminal pressure of local capillaries
inc exchange of nutrients/waste
anastomoses
lymph drain
all result in localized inflam
86pulp sensory nerve fiber types
myelinated axons: A-fibers (20%)
unmyelinated axons: C-fibers (80%)
87plexus of rashkow
smaller bundles of nerve in coronal pulp, in subodontoblastic cell free zone
88where do A-fibers terminate
below/around odontoblasts or alongside odontoblast process
89where do C-fibers terminate
pulp proper
90A-beta fibers
fastest conducting, for pressure and touch (proprioception)
91A-delta fibers
slower conducting, low threshold for excite, pain/temp/touch
SHARP PRICKING PAIN
92C fibers
slowest conducting, high thresholds of excite, pain
DULL ACHING THROBBING PAIN
93all sensory nerve fibers in pulp and dentin function as
nociceptors; all afferent impulses generate pain
94motor innervation of pulp
sympathetic post-gang efferent fibers, maintain vasomotor tone for pressure and distribution of pulpal blood flow
NO PARASYM IN PULP
95hydrodynamic theory
explains dentinal hypersensitivity
dentinal nociceptors are mechanoreceptors, activated by movement of fluid
fluid movt happens in response to painful stimuli
96inward flow of dentinal tubular fluid caused by
heat
97outward flow of dentinal tubular fluid caused by
cold, air, hyper-osmotic (sugary)
98what flow of tubule fluid cause stronger nerve response
outward flow
99endo cold testing activates what fibers
A-delta
100pulp stones classification
free stones
attached stones
embedded stones
101free stones are
surrounded by pulp tissue
102attached stones are
continuous w dentin
103embedded stones are
surrounded entirely by dentin, mostly tertiary
104calcifications are present in at least
50% of teeth
105calcification can happen on what kind of pulps
both normal and chronically inflamed
106pulp calcifications symptoms
none; not responsible for pain