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Oral biology > Dentin > Flashcards

Dentin Flashcards

1
Q

the space dentine occupies in pulp cavity is

A

coronal portion (pulp camber) and reticular portion (root canal)

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2
Q

pulp horn are prominent

A

buccal part of premolar and mesobuccal cusp part of molar

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3
Q

apical foramen in developing tooth

A

its wide and centrally placed

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4
Q

apical foramen in developed tooth

A

apical foramen becomes narrower in diameter and eccentric in portion (0.3 - 0.6 micrometer)

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5
Q

predentin

A

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

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6
Q

how predentin gets mineralized

A

when non collagenous matrix proteins get incorporated into predentin it mineralizes

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7
Q

mature dentin is made up of?

A

70% inorganic
20% organic
10% water

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8
Q

inorganic component of dentine is

A

hydroxyapatite

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9
Q

organic component of dentin is?

A

collagen ( TYPE I III AND V) and also have some non collagenous protein and lipids

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10
Q

how dentine appear on radiographs as compared to enamel and pulp

A

radiolucent than enamel (darker)

radiopaque than pulp (lighter)

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11
Q

dentine and enamel are bound at?

A

dentinoenamel junction and the junction appears scalloped

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12
Q

what are the types of dentine

A

primary
secondary
tertiary

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13
Q

primary dentine

A

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

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14
Q

secondary dentine

A

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

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15
Q

pulp recession

A

higher rate of deposition of secondary dentine around the floor and roof of chamber changes asymmetrical size and shape of the chamber

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16
Q

tertiary dentin

A

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

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17
Q

osteodentin

A

cells forming tertiary dentin either line its surface or become a part of dentine the latter is osteodentine

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18
Q

reactionary dentine

A

made by pre-existing odontoblast

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19
Q

reparative dentine

A

made by newly differentiated odontoblast like cells

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20
Q

pattern of dentin formation of crown/coronal

A

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

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21
Q

pattern of dentin formation of root

A

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.

22
Q

dentine development in deciduous tooth and permanent teeth

A

not until 18 months in deciduous

2-3 years after permanent have erupted

23
Q

formative organ and cells of dentine are

A

dental papilla and odontoblast

24
Q

odontoblast differentiation takes place how

A

it takes place by differentiation of odontoblast from dental papilla by signaling of molecules and growth factor

25
Q

procedure of odontoblast differentiation

A

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

26
Q

formation of mantle dentin

A

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

27
Q

enamel spindle

A

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

28
Q

how dentine mineralizes

A

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

29
Q

size of mantle dentine

A

15-20 micrometer

30
Q

the two patterns of mineraization

A

globular and linear

31
Q

globular mineralization

A

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

32
Q

linear mineralization

A

when the rate of formation progresses slowly, and the mineralization front appears more uniform which is known as linear

33
Q

formation of root dentin

A

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

34
Q

secondary dentin dentinogenesis

A

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

35
Q

tertiary dentin dentinogeneis

A

it is deposited at specific sites as a response to some injury or trauma

36
Q

what are dentinal tubules

A

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

37
Q

the curvatures (S SHAPED) in dentinal tubule are cause?

A

from the crowding of and the path odontoblast that they take to move to the center of the pulp

38
Q

dead tract

A

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

39
Q

peritubular dentine

A

the collar of tubule which are highly calcified are peritubular dentine
they are hype mineralized, contains little collagen

40
Q

sclerotic dentin

A

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

41
Q

reasons of sclerotic dentin

A
  1. deposition of many peritubular dentine
  2. deposition of mineral within the tubule without the formation of dentine
  3. deposition of mineral that occurs in viable presence of odontoblast process
  4. mineralization of process itself with tubular contents. including intratubular collagen fiber
42
Q

Intertubular Dentin

A

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

43
Q

interglobular dentin

A

the areas which are unmineralized or hypomineralized dentin where globular zones of mineralization failed to fuse
or failure of fusion of
calcospherites

44
Q

cause of formation of interglobular dentin

A

deficiency of vitamin D OR exposed to high level of fluoride (fluorosis)

45
Q

where interglobular dentin can be seen

A

circumpulpal dentin where globular mineralization is highest

46
Q

granular layer of tomes

A

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

47
Q

reasons for the formation of granular layer of tomes

A

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

48
Q

where odontoblast are found

A

near the surface of predentin where they form peripheral part of dental pulp.

49
Q

non collagenous matrix proteins present in dentin

A
  1. dentin phosphoprotein
  2. dentil sialoprotein
  3. dentin glycoprotein
  4. dentin matrix protein 1
  5. osteonectin, osteopontin and osteocalcin
  6. bone sialoprotein
  7. phopshoglycoportein
  8. proteoglycans
50
Q

pulp recession

A

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)

51
Q

sclerotic dentine is most common in

A

apical third of the root and the crown midway between DEJ and the pulp

Oral biology (6 decks)

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