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Histopathology > Class 4 Dentin > Flashcards

Class 4 Dentin Flashcards

1
Q

what are the structural components of dentin and their relative percentages

A

-70% mineral/inorganic
-20% organic
-10% water

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2
Q

what makes up the mineral/inorganic component of dentin

A

-calcium hydroxyapatite and trace amounts of calcium carbonate, fluoride, magnesium and zinc

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3
Q

what makes up the organic dentin matrix

A

-type 1 collagen with trace amounts of type 3 and 5
-50% non-collagenous proteins are phosphoprotein
-sialoprotein and silophophoprotien
-proteoglycans (biglucan and decorin) and glycosaminoglycans (chondroitin 4 sulfate and chondroitin 6 sulfate)
-osteonectin
-osteopontin
-receptor binding sequence arginine-glycine-asparagine (RGD) binding complex

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4
Q

what orientation does type 1 collagen in dentin run in relation to the basal lamina

A

parallel

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5
Q

what are the differences in type 1 collagen in dentin vs bone

A
  • higher ratio or proline and hydroxyproline
    -higher prevalence of molecular cross-linking
    -higher level of bound water
    -random orientation of the hydroxyapatite crystals
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6
Q

what are the life cycle stages of dentin

A

-pre-odontoblast
-secretory odontoblast
-transitional odontoblast
-resting odontoblast

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7
Q

what happens with fibronectin in the pre-odontoblast stage

A

-stimuli is derived from fibronectin from pre-ameloblasts located within the basal lamina of the inner enamel epithelium and growth factors derived from the IEE
-the fibronectin receptors on pre-odontoblasts allow the cells to align themselves along the basal lamina, assume polarity and differentiate into secretory cells

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8
Q

what do fibronectin receptor help do

A

align pre-odontoblasts along basement membrane with pre-ameloblasts on opposite side

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9
Q

what is odontoblast differentiation stimulated by

A

growth factors secreted by the IEE

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10
Q

what are the growth factors secreted by the IEE in odontoblast differentation

A

-transforming growth factor
- bone morphogenic protein
- IGF
-fibroblast growth factor

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11
Q

what happens in odontoblast differentiation in the pre-odontoblast stage

A

-complete differentiation of odontoblasts required a set number of replications to express necessary receptors to recognize growth factors
- the GF then help odontoblasts differentiate resulting in a mature odontoblast and a daughter cell that is forced into the subodontoblastic layer

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12
Q

what is the subodontoblastic cell layer and what is it responsible for

A

layer under the primed replicated pre-odontoblasts, “back up layer”, responsible for reparative dentin formation via reparative odontoblasts that differentiate from pulpal cells

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13
Q

what protects the subodontoblastic cell layer from growth factors

A

the layer above it

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14
Q

when is the subodontoblastic layer activated

A

when something injures the odontoblastic layer growth factors will trickle down to this layer causing maturation

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15
Q

describe the cells and their role in the subodontoblastic layer

A

they represent ectomesenchymal cells exposed to the entire cascade of developmental controls for odontoblastic differentiation except for the inductive influence of the growth factors with the IEE

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16
Q

describe the mature odontoblasts in the secretory odontoblast stage

A

tall columnar cells with extensive junctional complex and gap junctions formed

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17
Q

what do the mature odontoblasts in the secretory odontoblast stage do

A

-formation/crystallization of hydroxyapatite
-secrete type 1 collagen and trace type 3 and 5
- secrete matrix vesicles

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18
Q

how does formation/crystallization of hydroxyapatite by odontoblasts occur

A

significant alkaline phosphatase activity

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19
Q

what do the matrix vesicles secreted by odontoblasts contain

A

-alkaline phosphatase, phospholipids, phosphoproteins, pyrophosphatase
-calcium and phosphate
-annexin
-calcium hydroxyapatite crystals

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20
Q

what does annexin do

A

mediates flow of calcium into the matrix vesicle and serves as a collagen receptor that binds matric vesicles to collagen

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21
Q

what is mantle dentin and describe it

A

-first formed dentin
-50-100 um thick layer
- consists of type 1 and 3 collagen

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22
Q

how are the collagen fibers in mantle dentin arranged in orientation to the basal lamina of the IEE

A

perpendicular

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23
Q

what is the mantle dentin secreted by and then what happens

A

odontoblasts which then stimulates ameloblasts to secrete enamel matrix

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24
Q

how often is the organic matrix of dentin deposited

A

incrementally at a rate of 4-8 um per 24 hours

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25
Q

what are incremental lines in dentin and what is another name for them

A

-lines of von ebner
-represent a hesitation in matrix formation and subsequent altered mineralization that occured after 4-20 days of matrix deposition

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26
Q

what are neonatal lines/contour lines of owen

A

deficiencies and irregularities in dentiogenesis resulting in areas of hypomineralization in the dentin matrix

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27
Q

what are incremental lines in dentin a counterpart to and what does it occur

A

striae of retizius of enamel happening every 4-8 days

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28
Q

where are odontoblastic processes/dentin tubules located in the secretory odontoblast

A

extend out, trapped in dentin and branches out connecting to basal lamina. always remains connected with the basement membrane

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29
Q

where are anastomoses/branches in secretory odontoblast located

A

occurs as the tubule gets closer to the basement membrane. increases surface area/attachment points

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30
Q

what are the anastomoses/branches in the secretory odontoblast important in

A

bonding agents for composite

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31
Q

where does mineralization in dentin tubules occur

A

around the odontoblastic process

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32
Q

how are the dentin tubules tapered

A

narrower (0.9 um) near the DEJ and wider (2.5 um) as it nears the pulpal surface (and 1.2 um at mid-length)

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33
Q

dentinal tubules per unit area increases as ___

A

you reach the pulp due to pulpal chamber decreasing in size

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34
Q

where are dentinal tubules greater

A

near the pulpal surface (40,000) and about 20,000 near the DEJ

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35
Q

what are the types of dentin near the tubules

A

peritubular dentin and intertubular dentin

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36
Q

describe peritubular dentin

A

-more calcified/harder and more resistance to etch
-greater content of inorganic salts/more mineralized

37
Q

describe intertubular dentin and its location

A

demineralized
-located between the tubules

38
Q

what are the patterns of mineralization of dentin

A

linear
-globular/interglobular

39
Q

describe linear mineralization

A

calcified uniform manner and has solid appearance

40
Q

describe globular/interglobular mineralization

A

has areas of unmineralized and hypomineralized dentin between normal calcified dentinal layers

41
Q

where is globular/interglobular mineralization typically seen

A

in root surfaces and crowns of teeth

42
Q

does globular/interglobular mineralization indicate that somethings wrong

A

no just a different mineralization pattern

43
Q

what is tome’s granular layer

A

dentin that is formed globularly found in the root just adjacent to the cementum

44
Q

what is tomes granular layer used to distinguish

A

root dentin from crown dentin

45
Q

what is primary dentin

A

all the dentin (except mantle dentin) formed up to the time the tooth achieves functional occlusion

46
Q

what is secondary dentin

A

all the dentin formed (except tertiary/reparative dentin) formed after the tooth achieves functional occlusion

47
Q

what are dead tracts, what are they filled with and what do they look like

A

dentinal tubules that are void of the odontobalstic processes
-either filled with air or organic debris
-appear black in transmitted light microscope

48
Q

what is sclerotic dentin

A

dentin in which the tubules are occluded with mineral (no odontoblasts) the dentin is non-tubular and is nearly transparent

49
Q

when does sclerotic dentin occur

A

incidence occurence increases with increasing age of patient

50
Q

how often are incremental lines of von ebner depositied

A

increments of 4-8 um every 24 hours

51
Q

when do incremental lines of von ebner occur and what are they

A

4-20 days of matrix deposition and are thought to represent hesitations in matrix deposition and therefore altered mineralization

52
Q

what are contour lines of owen caused by

A

exaggerated von ebner lines caused by hesitations in maturation stages of the dentin

53
Q

what is the neonatal line

A

exaggerated von ebner line caused by trauma from birth
-whatever part of the tooth was forming at the time of birth will hold and then continue on

54
Q

what is tetracycline staining

A

lines/change in color of tooth occurs due to tetracycline taken at formation of certain tooth development

55
Q

what kind of stain results from tetracyclin

A

deep intrinsic stain

56
Q

what is reparative dentin/tertiary dentin

A

dentin deposited by newly differentiated odontoblasts at the site of pulpal trauma
-a defensive reaction attempting to wall off the pulp from the site of injury (caries)

57
Q

where does reparative/tertiary dentin form

A

when carious lesion reaches DEJ it will form at the pulp interface of the dentin

58
Q

what is the process of reparative dentin formation

A

cells in the subodontoblastic layer once exposed to growth factros released by stimulated pulpal cells differentiate and form the matrix of reparative dentin

59
Q

what is the goal of reparative dentin

A

wall off the site of injury and protect the pulp from more damage

60
Q

what is pulp capping/pulpotomy

A

process of removing infected pulp and pulp capping it. caused injury to pulp so a bridge of reparative dentin in root canal can form to protect the tooth and save it from having to get a root canal

61
Q

what is dentinogenesis imperfecta

A

hereditary defect that results in bluish gray teeth with an apalescent sheen

62
Q

describe the enamel and dentin in dentinogenesis imperfecta

A

-the enamel is normal but chips off due to lack of support by the abnormal dentin
- very little connection between enamel and dentin due to lack of enamel tufts

63
Q

describe the pulp chambers in dentinogenesis imperfecta

A

pulp chambers and canals are usually obliterated by defective dentin formation

64
Q

what is dental attrition due to bruxism

A

loss of wear of surface caused by tooth to tooth contact during mastication of parafunction

65
Q

which wears faster in dental attrition due to bruxism: enamel or dentin

A

same rate

66
Q

is dental attrition due to bruxism cold/temperature sensitive

A

yes

67
Q

what is dental erosion

A

loss of hard dental tissue by chemical processes

68
Q

describe what dental erosion looks like

A

-broad concavities with cupping of occlusal surfaces and dentin exposure
- incisal translucency as well as wear on non-occluding surfaces
- amalgam restorations appear raised and have non-tarnished appearance

69
Q

what is the caries balance

A

the balance between pathological and protective factors

70
Q

what does the hydroxyapatite core consist of

A

a more soluble carbonate apatite

71
Q

where does the carbonate subsitution occur in hydroxyapatite core

A

at the phosphate site

72
Q

what is the core of carbonated apatite eroded by

A

acids due to its greater susceptibility to dissolution

73
Q

what does fluoride replace and do in hydroxyapatite

A

may substitute hydroxyl ions in hydroxyapatite conferring greater stability and resistance to acidic dissolution

74
Q

how is bacteria responsible for dental caries (mechanism)

A

-bacteria ferments carbohydrates
-excrete acids
-acid attacks hydroxyapatite core and weakens it

75
Q

what bacteria are responsible for enamel and dentin caries

A

-streptococcus mutans
-streptococcus sorbinus
-streptococcus gorgonoid
-lactobacillus acidophilus

76
Q

what bacteria are responsible for root caries

A

actinomyces viscosus

77
Q

what is the dental caries process from enamel to dentin to pulp

A

enamel: a substantial cavitation is produced beneath the adjacent enamel surface. initally the caries lesion exhibits a small opening in the enamel and a pyramidal shaped dentin lesion with the apex of the pyramid pointing towards the tooth pulp
dentin: as it reaches DEJ it spreads laterally due to branching of dentinal tubules at the DEJ and then penetrates towards the pulp within the dentinal tubules
pulp: pulp necrosis can occur due to overwhelming of the pulpal tissue with carious lesions

78
Q

how much of the population is affected by dentinal sensitivity

A

1 in 5 people

79
Q

what teeth are most commonly affected by dentinal sensitivity and why

A

canine and premolars usually due to occlusal forces

80
Q

what stimuli are associated with dentinal sensitivity

A

-cold/hot beverages
-sweet/sour food
- aggressive brushing
-acidogenic plaque bacteria
-cosmetic bleaching of teeth
-clenching or bruxism

81
Q

what causes sensitivity in free nerve endings

A

excitability

82
Q

what are the dentinal sensitivity theories

A

-direct innervation theory
- transduction theory
- brannstroms hydrodynamic theory

83
Q

what is the direct innervation theory

A

direct stimulation of nerve endings in dentinal tubules

84
Q

what is the transduction theory

A

stimulation of odontoblasts that are coupled to nerves in the pulp

85
Q

what is brannstroms hydrodynamic theory

A

stimulation of dentinal tubules or exposed odontoblastic cell processes causes movement of tissue fluids within dentinal tubules that stimulate nerve endings in close associcated with dentin at the dentin/pulpal interface

86
Q

what is brannstroms hydrodyanmic theory rooted in and what is it

A

charles law- the volume of gas or fluid is directly protportional to the amount of heat applied at a constant pressure

87
Q

what does charles law say if heat is applied to the tooth

A

the volume of the fluid in the tubules increases stimulating nerve endings

88
Q

what does charles law say if cold is applied to the tooth

A

volume of fluid in the tubules decreases stimulating nerve endings

Histopathology (14 decks)

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