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Root development/periodontium Flashcards

(75 cards)

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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
cementoblasts secrete _____ that intermingle with dentin collagen fibers at the CDJ
initial collagen fibers
26
short initial collagen fibers are ____ and not yet connected with the PDL
intrinsic
27
the DCJ is a _____ interface between cementum and dentin
less hard "cushion"
28
the cervical loop defines the edge of the ____ during the bell stage; it is a ____ structure
enamel organ; crown
29
HERS defines the _____
forming root
30
composition of cementum
-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
31
physiology of cementum
- different from bone | - avascular, non-innervated, and no turnover (growth by apposition)
32
classic hypothesis for cementum origins:
ectomesenchyme > dental follicle > cementoblast
33
produce primary collagen fiber bundles of PDL space ; stitched to first cementum intrinsic fibers
PDL fibroblasts
34
extrinsic fibers will become mineralized ____ within cementum
Sharpey's fibers
35
____ fibers are the major fiber group for acellular cementum
extrinsic
36
extrinsic fibers enter acellular cementum at _____
high density
37
extrinsic fibers are critical to the ____ of acellular cementum
function
38
dense, highly organized Sharpey's fibers insert into both the ____ and _____
acellular cementum; alveolar bone
39
sharpey's fibers are _____ collagen fiber bundles, providing strong anchorage of _____
mineralized; tooth-PDL-bone
40
_____ promote hydroxyapatite deposition between and within collagen fibers
cementoblasts
41
maintains tooth in proper occlusal position by compensating for enamel attrition throughout life
"adaptive cementum"
42
____ can repair cementum resorption anywhere on the root
cellular cementum
43
cellular cementum mineralization begins with a clear, unmineralized _____
cementoid
44
cementoid is equivalent to ____ or ____
predentin; osteoid
45
in cellular cementum mineralization, ____ secrete collagen and other proteins, there is a ____, and then the matrix mineralizes
cementoblasts; time lag
46
embedded in cellular cementum matrix, connected to one another and the surface (PDL)
cementocytes
47
cellular and acellular cementum continue growing slowly throughout life, by _____ growth
appositional (adding to the existing layer)
48
deposited following root resorption by osteoclasts/odontoclasts
reparative cementum
49
reparative cementum fills ____/_____
resorption pit; Howship's lacuna
50
reparative cementum is often _____, regardless of location (i.e. even on cervical root)
cellular
51
rare skeletal disease, caused by mutations in ALPL, gene for tissue non-specific alkaline phosphatase (TNAP protein)
hypophosphatasia (HPP)
52
TNAP breaks down ____, an inhibitor of mineralization
pyrophosphate (PPi)- causes high levels of PPi
53
HPP causes ____ or ____
acellular cementum aplasia ; hypoplasia
54
HPP results in:
defective/absent acellular cementum: loose teeth, premature loss of primary and/or secondary teeth
55
excessive cementum growth from trauma, genetic disease, or idiopathic; generally asymptomatic, may cause ankylosis or difficulty in extraction
hypercementosis
56
protein important in acellular cementum mineralization; promotes hydroxyapatite mineral formation
bone sialoprotein (BSP)
57
bone lining the tooth socket, inner aspect facing the tooth root
bundle bone
58
bundle bone includes _____, mineralized _____ (similar to acellular cementum)
extrinsic collagen fiber bundles; Sharpey's fibers
59
primary fibers entering bundle bone are larger in _____ and less ____ (compared to cementum)
diameter; dense
60
radiographic feature of alveolar bone; radiopaque layer lining the socket
lamina dura
61
increased radiopacity from thick bone without _____, NOT because of increased mineral content
trabeculation
62
lamina dura is ____ and PDL is _____
radiopaque ; radiolucent
63
"mechanostat" theory of bone loading
bone loading causes growth (tennis player effect) | bone unloading causes loss (astronaut effect)
64
soft fibrous connective tissue between tooth and alveolar bone (i.e. occupies the periodontal space)
peridontal ligament (PDL)
65
PDL connects ___ to ____ in a unique joint called a ____, or tooth socket
tooth; bone; gomphosis
66
composition of PDL
- ground substance - collagen fibers - oxytalan fibers
67
collagen fiber bundles spanning PDL from mature tooth to bone
PDL principal fiber groups | exception is transseptal group which is tooth-tooth
68
the 6 principal fiber groups
``` transseptal alveolar crest horizontal oblique apical interradicular ```
69
____ group of principal fibers is predominant; main group resisting occlusal loads (intrusive force)
oblique
70
majority of cells in the PDL; secrete and remodel matrix
fibroblasts
71
fibroblasts are intimately associated with _____; cells may act as _____
collagen fibers; mechanotransducers
72
4 types of nerve endings identified in the PDL
1. free endings, tree-like (nociceptors and mechanoreceptors) 2. Ruffini endings (mechanoreceptors) 3. coiled endings 4. encapsulated endings
73
ectopic cementum in PDL; attached or unattached
cementicle
74
cementum-bone fusion; loss of PDL space
ankylosis
75
4 groups of gingival ligaments
circular dentogingival dentoperiosteal alveologingival

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