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Histo > Root development/periodontium > Flashcards

Root development/periodontium Flashcards

1
Q

Hertwig’s epithelial root sheath (HERS) is the “architect” of the root, defining ____ and ____ (morphogenesis); it also induces root _____

A

size; shape; odontoblast differentiation

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2
Q

multi-rooted teeth depend on epithelial growth through epithelial _____, in which tongues of epithelium grow toward one another

A

interradicular process(es)

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3
Q

size and shape of root(s) depends on HERS ____ and ____

A

cell migration; proliferation

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4
Q

in differentiation of the root, HERS induces ____ cells to differentiate into ____, then _____

A

dental papilla; pre-odontoblasts; odontoblasts

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5
Q

root dentin forms in step with _____

A

HERS proliferation

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6
Q

HERS is a ____ structure and ____ shortly after inducing root odontoblast differentiation

A

transient; disintegrates

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7
Q

some HERS cells become _____

A

Epithelial rests of Malassez (ERM)

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8
Q

ERM appear as clumps, strands, or networks of cells in the ____; surrounded by a _____

A

PDL; basement membrane

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9
Q

ERM can cause ____ and are also speculated to be involved with ____ or _____

A

cysts; periodontal homeostasis; regeneration

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10
Q

without ____, dental papilla cells cannot respond to HERS signaling and cells do not differentiate into odontoblasts; result is a rootless tooth

A

Nfic TF

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11
Q

defects of HERS growth and/or root dentin formation

A
  • “rootless tooth”
  • dilaceration: deformity in shape/direction of root
  • taurodontism: large pulp chamber at expense of root/furcation
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12
Q

cementum comes in 2 main types, defined by:

A
  1. presence/absence of cells within its matrix

2. origin of collagen fibers of the matrix

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13
Q

covers 2/3 of the root

A

primary acellular cementum (acellular extrinsic fiber cementum)

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14
Q

covers apical 1/3 of the root

A

secondary cellular cementum (cellular intrinsic fiber cementum)

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15
Q

a mix of alternating acellular and cellular layers

A

cellular mixed stratified cementum (CMSC)

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16
Q

cells in the cellular cementum

A

cementocytes

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17
Q

4 special functions of cementum

A
  1. attachment (acellular cementum primarily)
  2. protecting root from resorption/repairing resorption pits
  3. adjusting tooth position (cellular cementum only)
  4. sealing dentinal tubules
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18
Q

cementoblasts are thought to be derived from _____

A

dental follicle (ectomesenchyme)

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19
Q

products of cementoblasts

A

collagens, extracellular matrix (ECM) proteins, enzymes that promote mineralization of cementum

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20
Q

a subset of cementoblasts that become embedded in cellular cementum matrix (i.e. from dental follicle, ectomesenchyme)

A

cementocytes

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21
Q

cementocytes reside in ____ (small space in the matrix), extend _____ through _____ to communicate and receive nutrients

A

lacuna; dendrites (cell processes); canaliculi (small tunnels)

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22
Q

dental follicle is the precursor to:

A

cementoblasts, PDL fibroblasts, and osteoblasts

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23
Q

the “scaffold” for cementum formation

A

root dentin

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24
Q

just before cementum can form, ____ disintegrates, exposing root dentin surface

A

HERS

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25
Q

cementoblasts secrete _____ that intermingle with dentin collagen fibers at the CDJ

A

initial collagen fibers

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26
Q

short initial collagen fibers are ____ and not yet connected with the PDL

A

intrinsic

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27
Q

the DCJ is a _____ interface between cementum and dentin

A

less hard “cushion”

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28
Q

the cervical loop defines the edge of the ____ during the bell stage; it is a ____ structure

A

enamel organ; crown

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29
Q

HERS defines the _____

A

forming root

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30
Q

composition of cementum

A

-similar to bone and dentin
about 50% inorganic mineral: hydroxyapatite
about 35% organic (90% type I collagen; 10% non-collagenous proteins and GAGs
15% water

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31
Q

physiology of cementum

A
  • different from bone

- avascular, non-innervated, and no turnover (growth by apposition)

32
Q

classic hypothesis for cementum origins:

A

ectomesenchyme > dental follicle > cementoblast

33
Q

produce primary collagen fiber bundles of PDL space ; stitched to first cementum intrinsic fibers

A

PDL fibroblasts

34
Q

extrinsic fibers will become mineralized ____ within cementum

A

Sharpey’s fibers

35
Q

____ fibers are the major fiber group for acellular cementum

A

extrinsic

36
Q

extrinsic fibers enter acellular cementum at _____

A

high density

37
Q

extrinsic fibers are critical to the ____ of acellular cementum

A

function

38
Q

dense, highly organized Sharpey’s fibers insert into both the ____ and _____

A

acellular cementum; alveolar bone

39
Q

sharpey’s fibers are _____ collagen fiber bundles, providing strong anchorage of _____

A

mineralized; tooth-PDL-bone

40
Q

_____ promote hydroxyapatite deposition between and within collagen fibers

A

cementoblasts

41
Q

maintains tooth in proper occlusal position by compensating for enamel attrition throughout life

A

“adaptive cementum”

42
Q

____ can repair cementum resorption anywhere on the root

A

cellular cementum

43
Q

cellular cementum mineralization begins with a clear, unmineralized _____

A

cementoid

44
Q

cementoid is equivalent to ____ or ____

A

predentin; osteoid

45
Q

in cellular cementum mineralization, ____ secrete collagen and other proteins, there is a ____, and then the matrix mineralizes

A

cementoblasts; time lag

46
Q

embedded in cellular cementum matrix, connected to one another and the surface (PDL)

A

cementocytes

47
Q

cellular and acellular cementum continue growing slowly throughout life, by _____ growth

A

appositional (adding to the existing layer)

48
Q

deposited following root resorption by osteoclasts/odontoclasts

A

reparative cementum

49
Q

reparative cementum fills ____/_____

A

resorption pit; Howship’s lacuna

50
Q

reparative cementum is often _____, regardless of location (i.e. even on cervical root)

A

cellular

51
Q

rare skeletal disease, caused by mutations in ALPL, gene for tissue non-specific alkaline phosphatase (TNAP protein)

A

hypophosphatasia (HPP)

52
Q

TNAP breaks down ____, an inhibitor of mineralization

A

pyrophosphate (PPi)- causes high levels of PPi

53
Q

HPP causes ____ or ____

A

acellular cementum aplasia ; hypoplasia

54
Q

HPP results in:

A

defective/absent acellular cementum: loose teeth, premature loss of primary and/or secondary teeth

55
Q

excessive cementum growth from trauma, genetic disease, or idiopathic; generally asymptomatic, may cause ankylosis or difficulty in extraction

A

hypercementosis

56
Q

protein important in acellular cementum mineralization; promotes hydroxyapatite mineral formation

A

bone sialoprotein (BSP)

57
Q

bone lining the tooth socket, inner aspect facing the tooth root

A

bundle bone

58
Q

bundle bone includes _____, mineralized _____ (similar to acellular cementum)

A

extrinsic collagen fiber bundles; Sharpey’s fibers

59
Q

primary fibers entering bundle bone are larger in _____ and less ____ (compared to cementum)

A

diameter; dense

60
Q

radiographic feature of alveolar bone; radiopaque layer lining the socket

A

lamina dura

61
Q

increased radiopacity from thick bone without _____, NOT because of increased mineral content

A

trabeculation

62
Q

lamina dura is ____ and PDL is _____

A

radiopaque ; radiolucent

63
Q

“mechanostat” theory of bone loading

A

bone loading causes growth (tennis player effect)

bone unloading causes loss (astronaut effect)

64
Q

soft fibrous connective tissue between tooth and alveolar bone (i.e. occupies the periodontal space)

A

peridontal ligament (PDL)

65
Q

PDL connects ___ to ____ in a unique joint called a ____, or tooth socket

A

tooth; bone; gomphosis

66
Q

composition of PDL

A
  • ground substance
  • collagen fibers
  • oxytalan fibers
67
Q

collagen fiber bundles spanning PDL from mature tooth to bone

A

PDL principal fiber groups

exception is transseptal group which is tooth-tooth

68
Q

the 6 principal fiber groups

A 
transseptal
alveolar crest
horizontal
oblique
apical
interradicular
69
Q

____ group of principal fibers is predominant; main group resisting occlusal loads (intrusive force)

A

oblique

70
Q

majority of cells in the PDL; secrete and remodel matrix

A

fibroblasts

71
Q

fibroblasts are intimately associated with _____; cells may act as _____

A

collagen fibers; mechanotransducers

72
Q

4 types of nerve endings identified in the PDL

A
  1. free endings, tree-like (nociceptors and mechanoreceptors)
  2. Ruffini endings (mechanoreceptors)
  3. coiled endings
  4. encapsulated endings
73
Q

ectopic cementum in PDL; attached or unattached

A

cementicle

74
Q

cementum-bone fusion; loss of PDL space

A

ankylosis

75
Q

4 groups of gingival ligaments

A

circular
dentogingival
dentoperiosteal
alveologingival

Histo (14 decks)

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