Dentin Flashcards
the space dentine occupies in pulp cavity is
coronal portion (pulp camber) and reticular portion (root canal)
pulp horn are prominent
buccal part of premolar and mesobuccal cusp part of molar
apical foramen in developing tooth
its wide and centrally placed
apical foramen in developed tooth
apical foramen becomes narrower in diameter and eccentric in portion (0.3 - 0.6 micrometer)
predentin
dentin first deposits as a layer of unmineralized matrix which varies in thickness (10-50 micro meter) it mainly contains collagen and can be distinguished in histo slides as it stains less intensely
how predentin gets mineralized
when non collagenous matrix proteins get incorporated into predentin it mineralizes
mature dentin is made up of?
70% inorganic
20% organic
10% water
inorganic component of dentine is
hydroxyapatite
organic component of dentin is?
collagen ( TYPE I III AND V) and also have some non collagenous protein and lipids
how dentine appear on radiographs as compared to enamel and pulp
radiolucent than enamel (darker)
radiopaque than pulp (lighter)
dentine and enamel are bound at?
dentinoenamel junction and the junction appears scalloped
what are the types of dentine
primary
secondary
tertiary
primary dentine
most of the tooth is formed by primary dentine
the dentine around the pulp is circumpulpal dentine and the outer layer which is near the cementum or enamel is mantle dentine
secondary dentine
it forms after the tooth development has been finished, its more slow and gradual deposition
the organization of dentinal tubules less less organized and continuous with primary dentine.
the ratio of organic to mineral content is same
deposition of secondary dentine is less around the periphery
pulp recession
higher rate of deposition of secondary dentine around the floor and roof of chamber changes asymmetrical size and shape of the chamber
tertiary dentin
it is made due to a stimulus such as caries, trauma or attrition or restorative dental procedure. tertiary dentine is only produced by those cells which receive the stimulus
the quantity depends on cellular response initiated which depends on the intensity of the stimulus
osteodentin
cells forming tertiary dentin either line its surface or become a part of dentine the latter is osteodentine
reactionary dentine
made by pre-existing odontoblast
reparative dentine
made by newly differentiated odontoblast like cells
pattern of dentin formation of crown/coronal
papillary tissue adjacent to the folded inner enamel epithelium the place of cuspal development, is the site where dentin formation starts and it spreads downwards till the cervical loop of enamel organ and then it starts thickens till all the coronal dentin is formed
in multicuspal, same procedure happens within each cusp until fusion with adjacent formative center occurs
pattern of dentin formation of root
the formation of root dentine takes place at later stage of development, it involves proliferation of epithelial cells (HERS) from the cervical loop of enamel organ around the growing pulp to initiate the differentiation of root odontoblast
till the time the tooth take its functional position 2/3 of its dentine is formed.
dentine development in deciduous tooth and permanent teeth
not until 18 months in deciduous
2-3 years after permanent have erupted
formative organ and cells of dentine are
dental papilla and odontoblast
odontoblast differentiation takes place how
it takes place by differentiation of odontoblast from dental papilla by signaling of molecules and growth factor
procedure of odontoblast differentiation
the cells of dental papilla are undifferentiated and small and have central nucleus and small organelles, the space between the dental papilla and inner enamel epithelium is called acellular zone, once the cells of inner enamel epithelium reverse polarity changes take place in cell of dental papilla, the ectomesenchymal cells adjoin the acellular zone enlarge and elongate to become preodontoblast and then odontoblast
the acellular zone disappears as more cells differentiate into odontoblast
formation of mantle dentin
large diameter collagen fibers (von Korffs ) fibers which are assocated with collagen III and fibronectin, originate deep into odontoblast, extend into inner enamel epithelium and fan out into the stucterless ground substance below inner enamel epithelium, they also produce collagen type I that orients itself parallels to dentinoenamel junction and that hoe mantle predentin appears
enamel spindle
plasma membrane of odontoblast with adjacent ameloblast extend stubby processes into the forming extracellular matrix, these process interposing between the cells of inner enamel epithelium makes up the enamel spindle
how dentine mineralizes
matrix vesicles present near basal lamina, single crystal seeded by phospholipid ruptures and releases a cluster of crystallites joining the adjacent crystals making up a continuous layer of mineralized matrix
size of mantle dentine
15-20 micrometer
the two patterns of mineraization
globular and linear
globular mineralization
deposition of crystals in discrete area in matrix by heterogenous capture in collagen
it takes place usually in mantle dentin at different mineralization foci made by matrix vesicles. different globular masses are formed which in the end fuse together to form one whole mineralized mass
linear mineralization
when the rate of formation progresses slowly, and the mineralization front appears more uniform which is known as linear
formation of root dentin
it is formed by ODONTOBLAST differentiation initiated by HERS
outermost layer of root dentin which is equivalent to mantle dentin in crown, shows different in orientation and organization of collagen fibers, it is a slower process of deposition, the degree of mineralization is different from coronal dentin, and phosphoprotein content is different
secondary dentin dentinogenesis
its similar to that of primary dentin but it takes place after root formation has completed. it has a much slower pace of dentinogenesis, u can see a difference in staining, a demarcation, the arrangement of tubules are different, irregular and some places absent completely
as the layer becomes thicker the inner surface is reduced, odontoblast get crowded and die eventually
tertiary dentin dentinogeneis
it is deposited at specific sites as a response to some injury or trauma
what are dentinal tubules
odontoblastic process that run on canaliculi that transverse the entire length of dentine. they cover the entire thickness of dentine from the dentinoenamel junction to the minelization front. tubules follow an S shaped path
the curvatures (S SHAPED) in dentinal tubule are cause?
from the crowding of and the path odontoblast that they take to move to the center of the pulp
dead tract
tubules in carious lesions may fill up with bacteria and appear darkly stained in histo slides
the process in these tubules may disintegrate or retract leaving air spaces behind which is called as dead tract
peritubular dentine
the collar of tubule which are highly calcified are peritubular dentine
they are hype mineralized, contains little collagen
sclerotic dentin
dentinal tubules that have become highly calcified. when this occurs in many dentinal tubules at the same time the dentine gives a glassy translucent appearance. sclerotic dentin increases with age
reasons of sclerotic dentin
- deposition of many peritubular dentine
- deposition of mineral within the tubule without the formation of dentine
- deposition of mineral that occurs in viable presence of odontoblast process
- mineralization of process itself with tubular contents. including intratubular collagen fiber
Intertubular Dentin
the dentin between the dentinal tubules. it contains the formative product of odontoblast and makes interwoven network of type I collagen fibers around which apatite crystals are deposited
the ground substance has non collagenous matrix proteins and plasma proteins
interglobular dentin
the areas which are unmineralized or hypomineralized dentin where globular zones of mineralization failed to fuse
or failure of fusion of
calcospherites
cause of formation of interglobular dentin
deficiency of vitamin D OR exposed to high level of fluoride (fluorosis)
where interglobular dentin can be seen
circumpulpal dentin where globular mineralization is highest
granular layer of tomes
under trasmitted light in ground section u can see granular area right below dentin where the cementum covers the root. porgessive increase in granulaity increase from cementoenamel junction to the apex of the tooth
reasons for the formation of granular layer of tomes
it was believed to be associated with hypomineralized areas of interglobular dentine
or true spaces
later it was know to be the looped terminal portions of dentinal tubule of only root dentin which shows granulation due to refraction of light
latest studies show its the arrangement of collagenous and non collagenous matrix protein between the dentin and cementum
where odontoblast are found
near the surface of predentin where they form peripheral part of dental pulp.
non collagenous matrix proteins present in dentin
- dentin phosphoprotein
- dentil sialoprotein
- dentin glycoprotein
- dentin matrix protein 1
- osteonectin, osteopontin and osteocalcin
- bone sialoprotein
- phopshoglycoportein
- proteoglycans
pulp recession
the deposition of secondary dentin around roof and floor of the chamber leads reduction in size and shape of pulp chamber
( old people have more pulp recession than young people)
sclerotic dentine is most common in
apical third of the root and the crown midway between DEJ and the pulp
