Dentin Histology COPY Flashcards
Physical properties of dentin
color-slightly yellow, enamel appears white
Composition of dentin
HAP (inorganic) -70%
Type 1 Collagen fibers (organic)-20%
Water-10%
What gives tooth its color
dentin
How much of the pulp does dentin cover
All of it
Function of dentin as it pertains to enamel
shock absorber for enamel (less mineralized and less brittle)
T/F, dentin is calcified?
T
The organic matrix of dentin is primarily composed of what
collagen type 1 (~90%)
In order of most to least mineralized tissue
Enamel > Dentin > Cementum > Bone
______ induce odontoblast polarization @ inner enamel epithelium (dentin of crown)
ameloblast
Where dentin formation begins and in which direction
DEJ and moves towards pulp
Odontoblasts form dentin in two stages:
(2)
substance is added (1) organic matrix is deposited
(2) an inorganic mineral
Responsible for root development
Hertwig’s epithelial root sheath
Primary dentin (when is it developed? What is it composed of?)
developed prior to eruption
composed of mantle and circumpulpal dentin
Interglobular dentin
Peritubular and intertubular dentin
Secondary dentin (when is it developed/what is it composed of?)
After eruption
circumpulpal dentin
tertiary dentin (when is it developed/what is it composed of?)
after eruption, caused by stimuli
Reactionary/response dentin
Reparative dentin
Osteodentin
Sclerotic dentin
Mantle dentin (when does it arise)
during initial phase of dentinogenesis-it is the first dentin formed
Mantle dentin is a product of what type of odontoblasts
immature-not fully differentiated
mantle dentin extends how far (range) pulpwards
10 to 30 µm up to 150 µm
Mantle dentin is composed of what type of collagen fibers
large collagen fibers
Mantle dentin mineralization
less mineralized than later formed circumpulpal
what happens after odontoblast form mantle layer?
with formation of this first layer of dentin, odontoblasts begin to draw away from inner enamel epithelium
Where does mantle dentin interact with enamel
DEJ,
Primary dentin-circumpulpal dentin (rate of formation and mineralization)
fast formation-4um/day
highly mineralized
Secondary dentin circumpulpal dentin (rate of formation and mineralization)
Slower formation-1um a day
less mineralized than primary dentin
Thickness of circumpulpal dentin
6-8 mm thick
With age what happens to the pulp
shrinks as dentin grows
collagen fibers of circumpulpal dentin
collagen fibers (50 - 200 nm) are 10 times smaller than in mantle dentin, parallel to DEJ
non mineralized dentin
predentin
types of mineralized dentin (2)
peritubular and intertubular dentin
intertubular dentin (function)
connects the dentinal tubules
Odontoblasts are part of the pulp tissue. Dentin and pulp are _________
“functional units”.
Shape of dentinal tubules?
S-Curved
dentin moves in which direction as it forms
pulpwards
how dentin tubules form
as a result of dentin lengthening as the odontoblast move
Where do dentinal tubules start
@ DEJ but may extend into forming enamel matrix=enamel spindles
Tomes’ Fibers
occupied by odontoblastic processes
How many processes do odontoblast initially have
multiple
after final differentiation secondary processes are within _______ ??
canaliculi
are dentinal tubules living tissue? is there communication?
yes
From the pulp to the DEJ, dentinal tubules _______
density and diameter of tubules decreases
intratubular dentin
Dentin that is located between or around the dentinal tubules
Known as the body of the dentin
intratubular dentin
composition of intratubular dentin (compare to peritubular)
same mineral and organic components like peritubular dentin, but less calcified
Changes to the intratubular dentin overtime
little change through life
Process of dentin getting mineralized?
Predentin-mineralized-predentin-mineralixed etc
first, organic matrix is deposited, and second, inorganic mineral substance is added
Predentin
newly formed, unmineralized matrix at pulpal border
Predentin mineralization occurs at the ________
PD-D junction (pre-dentin-dentin junction)
After occlusion and function secondary dentin is formed and only______ dentin is deposited and calcified each day
1.0 to 1.5 µm/d
Formation of circumpulpal dentin continuous?
NO
„resting phases“ appear how in dentin
in demineralized sections of dentin as lines
distance between incremental lines
20um
width of incremental lines
width varies from 8 µm coronally to 3 µm apically
direction of incremental lines
right angle to tubules
Official name for incremental lines
„incremental lines of von Ebner“
or hypocalcified bands
incremental lines are
equivalent to incremental lines of
Retzius in enamel
How contour lines of owen form
metabolic disturbances during dentinogenesis affects the formation of matrix and mineralization of dentin
caused by birth (=neonatal line) or by systemic diseases during childhood years
width depends of the duration of cause
where do contour lines of owen occur
occur at irregular intervals and in variable numbers
Contour lines of owen first described by who
first described from Sir Richard Owen (1804-1892), Anatomist in London
Vitality can be defined as ability to react to physiologic and pathologic stimuli.
(2)
- Pain perception
2. Functional adaption
Functional adaption: of vitality includes
secondary dentin, tertiary dentin, dentin sclerosis ???
Tertiary dentin and dentin sclerosis also part of
defense mechanisms
dentin sclerosis
Thickening of peritubular dentin and (up to) complete obliteration of dentin tubules
deposition of apatite crystals and collagen in dentinal tubules caused be irritating stimuli (e.g. caries, attrition, erosion, cavity preparation) blocking of tubules = defensive reaction also aging process sclerotic dentin appear light in ground sections vs. dark areas = dead tracts
Wtf does that mean
How can you kill odontoblast during a prep
overheating with not enough water irrigation
Dead tracts
what, how are they caused
represents empty, air filled tubules due to degeneration of odontoblastic process (caries, erosion, attrition)
dentin trauma cause the odontoblastic processes within the dentinal tubules to „die back“ toward cell body in severe cases even odontoblasts may die
Tertiary dentin (from what, where?)
results from pulp stimulation only in localized areas along dentin-pulp interface
what does the presence of tertiary dentin mean
correspond to those zones of dentin where tubules have been exposed peripherally through attrition, erosion, caries, or therapeutic interventions
clearly demarcated boundary
reactionary/response = deposition by odontoblasts
reparative = newly recruited odontoblasts (from undifferentiated cells of the pulp)
dentin adhesive and restorations
adhesives stay on enamel b/c it is mostly mineral and can etch- dentin is 10% water and 20% organic matrix so it is hard to adhere
Prep dentin, what do you have after prep?
a smear layer
What to do with smear layer of dentin after prep
etch it to remove it
