dentin(✿◡‿◡) Flashcards
covered everything❤️
what does dentin form in tooth
bulk of tooth , providing shape and structure also its the only living hard tissue in body “ vital”
dentin location
beneath enamel and covered by cementum in root
what are the junctions of dentin with other dental tissues
-dentin meets enamel at DEJ which is scalloped for strong attachment
-dentin meets cementum at DCJ which is less distinct and may be smooth
what is the dentin -pulp complex
dentin and pulp are closely related embryologically , histologically , and functionally forming integrated complex
how does pulp contribute to dentin
pulp provides vitality to dentin and stimulates dentin formation
is dentin cellular or acellular
cellular contains odontoblastic processes
does dentin have ability to repair itself
yes through secondary and tertiary dentin formation
is dentin vascular or avascular
avascular
what color is the dentin
light yellow and darkens with age due to the continuous deposition of secondary dentine
why is dentine flexible
because it contains collagen and this helps prevent enamel fracture by absorbing masticatory forces
how does dentin resistant to wear compare to enamel
dentin is less resistant to attrition , abrasion, and erosion than enamel
how does dentin permeability change over time
decreases with age due to narrowing of dentinal tubules
what is the radiographic appearance of dentin
dentin appears more radiolucent than enamel but more radiopaque than pulp
what are the compressive strength and tensile strengths of dentin compared to enamel
enamel: high compressive strength, low tensile strength
dentin: high tensile strength , low compressive strength
what is the chemical composition of dentin
70% inorganic
20% organic
10% water
what is main inorganic component of dentin and its chemical formula
hydroxyapatite crystals ( smaller than enamel) Ca10(PO4)6(OH)2
what are the organic components of dentin
90% collagen fibrils( Type I, III,V)
10% non collagenous proteins and lipids
what are the proteins found in the organic portion of dentin
dentin phosphoprotein
dentin sialoprotein
dentin matrix protein
osteonectin
osteocalcin
osteopontin
bone sialoprotein
proteoglycans
what is the role of collagen in dentin
provides rigidity
Type I acts as scaffold for mineral deposition
what is the function of phosphoproteins in dentin
binds calcium and collagen
initiate crystal formation
what is the function of sialoprotein
inhibit crystal growth in peritubular dentin to prevent tubule occlusion
what’s the function of phospholipids
role in mineralization and in pre dentin and dentin
what are the results from DSPP mutation
dentinogesnsis imperfecta
how do proteoglycans contribute to dentin mineralization
more in predentin, prevents premature mineralization until collagen reach their final dimension
compare enamel and dentin hardness
enamel: is the hardest in body, 97 % mineralized
dentin : less hard than enamel but harder than cementum and bone, 65% -70% mineralized
what is role of enzymes in dentin
catalyze reactions in dentin matrix
what gives dentin its yellowish color
its composition and mineralization which is less dense than enamel
what is a unique property of secondary dentin
its formed throughout life
what is the role of growth factors in dentin
induce tertiary dentin production
how does dentin contribute to tooth sensitivity
dentin contains tubules connected to pulp which can transmit sensations of pain and sensitivity
how does dentin permeability impact dental treatment
it allows therapeutic agents applied to its surface to diffuse toward pulp aiding in treatments like remineralization
what are the main categories of dentin according to time of formation
primary dentin ( predentin , mantle dentin , circumpulpal dentin)
secondary dentin
what are types of dentin related to dentinal tubules
peritubular dentin and intertubular dentin
what types of dentin form in response to injury
tertiary dentin ( reparative and reactionary)
sclerotic dentin
dental tract
what is sclerotic dentin and when does it form
Sclerotic dentin forms when dentinal tubules become occluded with minerals, usually due to aging or chronic irritation
what is dead tract in dentin
its an area where dentinal tubules lose their odontoblastic processes due to damage or death of odontoblast often appearing dark under microscope
define interglobular or globular dentin
type of dentin characterized by areas of incomplete or defective mineralization
what is primary dentin
dentin formed during initial development of tooth and ending when root formation is complete
what are layers of primary dentin
outermost is mantle
main bulk is circumpulpal dentin
reactionary dentin
forms from original odontoblast cells in response to mild irritation
reparative dentin
formed by newly recruit odontoblast like cells after significant damage
what triggers secondary dentin formation
begins after root formation is complete with continuous deposition of dentin
how does secondary dentin affect pulp chamber
causes pulp chamber to decrease in size over time
what structural difference exist between primary and secondary dentin
secondary dentin has fewer tubules and a demarcation line between secondary and primary dentin
what is the clinical significance of secondary dentin deposition in elderly people
as secondary dentin is deposited the pulp horn recede and in elderly patients this reduces the chance of pulp exposure during cavity prep (So, even though it shrinks the pulp space, it’s making a thicker protective layer to help prevent pulp exposure if the tooth gets damaged.)
what is mantle dentin
outermost layer of dentin , closest to enamel just below DEJ
what is the thickness of mantle dentin
20 microns
what unique fibers are found in mantle dentin
kroffs fibers which is large collagen fibers of type III
where is predentin located
layer closest to pulp
is pre dentin mineralized
no its nonmineralized
how thick is predentin
2-6 microns
what happens to predentin overtime
it mineralizes to become circumpuulpal dentin with new predentin forming beneath it
what triggers formation of tertiary dentin
injury to tooth, such as caries, attrition, abrasion, or cavity prep
how does rate of tertiary dentin formation relate to severity of injury
rate of deposition is related to severity of injury
where is the tertiary dentin located
it can form anywhere along the pulp-dentin complex
characteristics of tertiary dentin
fewer dentinal tubules
irregular arrangement
may contain no tubules or have cellular inclusions (osteodentin)
how many dentinal tubules and its more where
number varies from 30,000-70,000 and its more in crown than root
what is the diameter of dentinal tubules
broader(3 μm) near pulp and narrower (1μm) near enamel
dentinal tubules are extension of what
extension of odontoblast processes in pulp into DEJ and DCJ
what is the shape of dentinal tubules
curved ( S shape)
what are the two types of branching in dentinal tubules what does it do
lateral branching (canaliculi) its 1μm in diameter and terminal branching and they allow permeability of dentin and pathways for microbial invasion
what are the curvature of dentinal tubules
primary curvature: represent odontoblast movement toward pulp during dentinogensis which is less prominent in roots and straight in incisal edge, cusps, and root tips
secondary curvature: minor curvature representing daily odontoblast movement during dentogensis
what are the components of dentinal tubules
odontoblastic processes ( microtubule and filaments )
dentinal fluid
thin nerve fibers
peritubular dentin
lamina limitans ( organic lining rich in gag serves as junction between peritubular and dentin tubules)
what are enamel spindles
extensions of odontoblastic processes into enamel crossing DEJ
how do enamel spindles form
odontoblasts fail to withdraw quickly across DEJ during dentin so they get trapped
what is interglobular dentin
zones of hypomineralized dentin due yo incomplete fusion of mineral globules
what are other secondary causes of interglobular dentin
vitamin D deficiency during dentin formation and increased fluoride content
where is the interglobular dentin found
circumpulpal beneath mantle dentin
define Tomes granular layer and located where
granular layer in dentin at DCJ caused by intermingling or looping of tubules
how does Tomes granular layer appear
black granules, clearer in ground section, increases from CEJ to root apex
what are dead tracts
dark areas in dentin due to complete loss of odontoblastic processes from tubules so becomes filled with AIR and seen in older teeth
how do they appear
Black in transmitted light
White in reflected light
what causes dead tracts
attrition
severe injury
what do we have below dead tracts
tertiary dentin
sclerotic dentin
tubules occluded with minerals to protect pulp its appears glassy and transparent seen in elderly teeth and especially roots
Incremental lines of Von ebner
rhythmic deposition of dentin at rate 4μm/day and these lines are 20μm apart representing 5 days of deposition
lines occurs due to slight change in collagen and the lines run perpendicular to tubules
neonatal line
line separating prenatal which is better quality and postnatal dentin
found in deciduous teeth and 1st permanent molars
contour lines of OWEN
dark bands caused by deficiencies in mineralization due to illness or metabolic changes
is contour lines periodic like Von ebner lines
NOOOOO. cuz the contour lines occur due to specific events not periodic deposition like von ebner.
what is direct innervation theory
that stimuli directly affect the nerve endings in dentinal tubules
but the mechanism is unknown since nerve ending only extend only till inner dentin
what is transduction theory
that the odontoblast which originate from neural crest cells act as receptor and stimuli excite odontoblastic processes which will make impulses transmit to nerve endings.
this theory not widely accepted cuz of the absence of neurotransmitter vesicles in odontoblast
what is fluid hydrodynamic theory
most widely accepted
stimuli causes fluid movement within dentinal tubules and this movement disturbs nerve endings associated with odontoblast processes triggering PAIN through MECHANICAL DISTURBANCE
