dentin structure Flashcards
what forms a protective covering for the pulp and supports the overlying enamel and cementum
dentin
T/F
dentin is acellular, avascular, limited repair, no remodeling, located in crown and root and depositied over life of tooth
TRUE
what is the chemical composition of dentin
70 in-org
20 org
10 water
are the non-fib and fib the same proteins as in enamel and cementum?
NO! totally different ones
T/F
dentin has less elasticity and tensile strength than enamel
FALSE
it has more elasticity and tensile strength than enamel due to collagen!
is dentin permeably?
yes
2 regions of dentin
coronal and radicular
what are the 2 types of coronal dentin
mantle and circumpulpal
what are the 2 types of radicular dentin
hyaline layer of hopewell smith and circumpulpal
is peritubular dentin low or highly mineralized
highly!
hypomineralized regions in CROWN
mantle dentin and interglobular dentin
hyperminerzliaed regions in CROWN and ROOT
sclerotic
hypomineralized regions in ROOT
granular layer of tomes and may have some interglobular too
when does deposition of coronal dentin start
Deposition starts at end of bell stage through apposition (pre-eruptive)
when does deposition of radicular dentin start
Deposition starts during root formation (pre-functional
eruptive; Intraosseous )
does coronal dentin have a fast or slow rate of deposition
fast
does radicular dentin have a fast or slow rate of depostion
slower
what is deposited during pre-eruptive phase and pre-functional eruptive phase
primary dentin
what is the outer layer of dentin closest to DEJ ; first mineralized ( 3-5% less mineralized vs rest of crown) 0.15- .0.20 mm thickness in crown
and collagen fibers-deposited in crown perpendicular to DEJ
MANTLE dentin
what Surrounds pulp chamber - recognized in both crown and root
o Collagen fiber tightly packed arranged parallel to long axis of tooth 6-8 mm in thickness in crown/ thinner in root
* Slower rate of mineralization/ deposition than mantle
* Regular arrangement of dentin tubules –
* S-shaped curve in crown ( due to odontoblasts crowded)
* Horizontal rows in root (perpendicular to cementum )
circumpulpal dentin
what is deposited after root formation is complete and tooth is in occlusion;- (post-eruptive) secondary and triggered by physiological stimuli i.e aging, occlusal forces; abrasive foods
SECONDARY dentin
what dentin is deposited over life of tooth
secondary dentin
what is deposition triggered by pathological stimulus – (post-eruptive
tertiary dentin
what type of dentin is put down in response to caries, restoration, attrition and erosion and is it fast or slow
reactionary dentin
SLOW deposition
what type of dentin is put down in response to serve injury or OB die and is it fast or slow
reparative dentin
slow to react but FAST depostiion
Crystals that fail to coalesce and mineralize form hypomineralized regions called
interglobular dentin
what are the 2 patterns of dentin mineralization
- globular 2. linear
what represent the weekly deposition of dentin
* Lines appear at right angles to dentin tubule
Incremental Lines of Von Ebner
can we see Incremental Lines of Von Ebner
NO!
what are exaggered lines of Von Ebner called
contour lines of owen
what represent accentuated incremental lines (Von Ebner) which occur due to changes in mineralization over time
* Appear as wide lines run perpendicular to dentin tubules
contour lines of owen
what appears as line demarcating tertiary dentin at point of injury.
Calciotraumatic line
what appears yellow when viewed by transmitted light – tetracycline binds to calcium of hydroxyapatite crystals
tetracycline bands
once 8 y/o, cannot get anymore
what are are hypomineralized regions that show the “trauma of birth” and disrupts the incremental deposition of the enamel and dentin in the crown.
The line demarcates the boundary between the prenatal and postnatal periods of hard tissue deposition
neonatal lines
function of dentin tubules
allows for diffusion of nutrients
what do dentin tublues look like at the crown
s shaped
what do dentin tubules look like at the root
straight lines but bends at CDJ = granular layer (hypominerlaized)
contents of dentin tubules
- Odontoblastic process
- Unmyelinated sensory nerves endings extend short distance from pulp into tubule
- Dentinal fluid
what are dead tracts
-Empty dentin tubule –odontoblastic process disintegrates/ retracts
-Increase with age due loss of odontoblasts cell numbers
-Site of bacteria entry into pulp
-Visible by light microscopy – appear black due to air in Dry Ground section
-Often appears in association with sclerotic and tertiary
_____________ seals off such dead tracts at their pulpal extremity, thereby protecting the pulp from infection
Reparative dentin
region between the tubules
intertubular dentin
where is intertubular dentin
in crown and root in circumpulpal region
region of dentin that forms wlal of tubule
peritubular dentin
is peritubular dentin hypo or hypermineralizaed
hypermineralized
is peritubular found in interglobular dentin
NO
where can you find peritubular dentin
crown and root
in caries attack, one of the first regions demineralized is ______________– outcome is increased tubule diameter and faster spread of toxins and bacteria.
peritubular dentin
dentin tubules become filled with hypermineralized dentin
sclerotic dentin - aging
region where calcospherites failed to fuse
interglobular dentin
hypomineralized!!
region where dentin tubules meet cementum and hypomineralized in root, closet to CEJ.
ONLY visible in dry ground!
granular layer of tomes
Salt and pepper
-represents the interface between the dentin and cementum
* First layer deposited in ROOT formation but is delayed in completing mineralization until cementum is deposited.
hyaline layer of hopewell smith
last place mineralized
age related changes in dentin
- thickness due to 2 and 3 dentin
- decrease in permeability
- increase response rate to attrition/caries
- decrease in ability to repair
