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Embryology > PDL > Flashcards

PDL Flashcards

1
Q

PDL is a ____ CT structure

A

fibrous

*despite being fibrous in nature; it is also has many cells

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2
Q

is the PDL vasculaized and innervated?

A

YES!

-cementum is not

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3
Q

the thin PDL connects?

A

cementum layer to adjacent alveolar bone

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4
Q

where is the thinnest portion of PDL?

A

thinnest portion around middle third of root

*0.15-0.38mm

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5
Q

principle function of PDL?

A
  • supporting teeth in their sockets while permitting them to withstand forces of mastication
  • *sensory receptor for positioning of jaw (full of nociceptors)
  • remodeling for resorbing function
  • nutritive function due to being well-veascularized
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6
Q

principle fibers of the PDL form

A

strong fibrous union between teh root cementum and the bone

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7
Q

ankylosis

A

fusion of root to bone

*PDL fibroblasts may inhibit mineralization so this doesn’t occur

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8
Q

Name and describe the 5 PDL type 1 collagen fibrils bundles called?

A

1) alveolar crest group
- -below CE junction, down, out
2) horizontal group
- -right angle to root surface, apical
3) oblique group
- -oblique angle, coronally towards bone
4) periapical group
- -around apex, base of socket
5) interradicular group
- -in multirooted teeth at crest/furcation

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9
Q

PDL extracellular substances?

A

1) fcollagen fiberes
2) oxytalan fibers
3) glycosaminoglycans and glycoproteins (ground substance)

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10
Q

pressure-tension hypothesis

A

showing tooth displacement leading to compression and tension in the surrounding bone

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11
Q

alveolar bending hypothesis

A

tooth movement causing bending of the alveolar bone

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12
Q

stretched fibre hypothesis**

A

stretching and compression of PDL fibres leading to low and high strain areas in the surrounding bone

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13
Q

name and describe the 5 gingival ligament fibers’s fibers are imbedded

A

1) dento-gingival
- -most numerous, cervical cementum to free/attached gingiva
2) bone of the alveolar crest to free/attached gingiva
3) circular
- -around neck of teeth, free gingiva
4) apically over cementum over the outer cortical plate to alveolar process or vestibule of mouth
5) trans-septal
- -cementum between adjacent teeth, over the alveolar crest

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14
Q

bundle bone

A

where unraveled PDL fibers inter mesh with adjacent fibers and insert into the bone
*contain Sharpey’s fibers

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15
Q

define reversal line

A

location where the last cycle of bone resorption was followed by bone deposition
*the latter resulted from the production by osteoblasts of a thin seam of new bone in which very short Sharpey’s fibers are imbedded

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16
Q

TEM of periodontal ligament fibroblasts are responsible for?

A

1) synthesis of collagen and its assembly into collagen fibers
2) removal of collagen fibers during the continuous remodeling

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17
Q

digestive vacuoles majoridly remove?

A

collagen

*aka intracellular collagen in digestive vacuole

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18
Q

collagen fibrils are digested by _____ enzymes that have been added to the vacuoles

A

lysosomal enzymes

*the presence of these enzymes has been confrimed by cytochemical localization

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19
Q

are neural elements myelinated or not?

A
  • myelinated near the apical end

* unmyetlined more coronally

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20
Q

most of the neural branches near the apical end are?

A

MIXED. consisting of myelinated and non-myelinated axons

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21
Q

the distribution of nerve bracnhes is closely associated with that of?

A

blood vessels

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22
Q

PDL is rich in blood supply originating primarily from? communicating with what vessels?

A
  • *originating off dental arteries that enter through the apical foreman, LOTS of anastomoses
    • ligament vessels also communicate with supraperiosteal vessels
23
Q

the PDL contains an assortment of cells that are capable of generating and maintaining 3 distinct tissues. What are they?

A

1) ligament itself
2) mineralized tissues
3) alveolar bone

24
Q

what are the major cell types of PDL?

A

1) osteoblasts
2) osteoclasts
3) fibroblasts =MOST ABUNDANT
4) epithelial cells= hertwigs
5) macrophages= defense
6) undifferenciated cells
7) cementoblasts
8) vascular elements
() neural elements

25
Q

What is unique about mineralization and Sharpeys fibers?

A

one end of the fiber may be un-mineralized while the part IN the bond is mineralized— ONLY the mineralized part is referred to as Sharpey’s fiber

26
Q

cementoblasts provide?

A

ground substance that will imbed the fibers and allow mineralization to proceed

27
Q

formation of mature PDL

A
  • earliest remodeling along tooth and alveolar bone
  • grow thicker and longer, bone side is wider, until they meet
  • become organized once they meet
28
Q

fibroblasts are characterized by an ability to achieve an exceptionally high rate of?

A

turnover of proteins within the extracellular compartment (like collagen)

29
Q

what do integrins do?

A

bind ECM, serve as mechnotransducers to transmit the stimulus to the cell

30
Q

stimulus for ECM production?

A
  • mechanical stress

- changes in tensile and compressive forces during growth

31
Q

decrease in mechanical stress leads to?

A

increased collagenase secretion and a thinning of PDL

32
Q

epithelial cells in PDL resemble?

A

HERS (epithelial cell rests of Malassez)

*

33
Q

importance of undifferentiated mesenchymal cells?

A

theyare periovascular! differenciate into fibroblasts, osteoblasts, and cementoblasts

34
Q

what are the predominant collagens of PDL

A

1,3, 12

35
Q

what are the tyeps of elastin fiebrs

A

1) oxytalan- perpendicular to teeth

2) eluanin- found within gingival ligament

36
Q

does PDL contain immature or mature elastin protein?

A

immature forms of oxytalan and eluanin

37
Q

oxytalan fibers

A
  • thought to regualte vascular flow
  • dense in cervical region of ligament
  • associated with nueral and vascular elements
  • perpendicular to teeth OR vertically from cementum surface of root apically
38
Q

1) nerve supplu originates from?

2) enters from?

A

1) inferior or superior alveolar nerves
2) apical region and lateral socket walls
* *apical region contains more nerve endings

39
Q

interstital space

A
  • present between each bundle of ligament fibers
  • contains blood vessels and nerves
  • designed to withstand the impact of masticatory forces
40
Q

ground substance

A

-amorphous, highly hydrated ~70% water

41
Q

nature of ground substance explains?

A

why the PDL never mineralizes as it acts as an inhibitor for the process

42
Q

major ground substance components

A

1) glycosaminoglycan- hyaluronan and dermatan sulfate
2) proteoglycans- proteodermatan sulfate, decorin, biglycan
3) glycoproteins- fibronecin, tenasin and vitrabectib

43
Q

ground substance is critical for withstanding?

A
  • forces
  • ion water binding/exchange
  • binding to growth factors
  • collagen synthesis
  • fiber orientation
44
Q

PDL gets its blood supply from?

A

perforating arteries (from the cribiform plate of the bundle bone)

45
Q

is the posterior or anterior supply of blood greater?

A

posterior

46
Q

ligament in thicker in functioning or non-functioning teeth?

A

functioning and in areas of greater tension

47
Q

ligament cells are capable or remodeling the ligaement and adjacent?

A

bone

48
Q

PDL protects the tooth from normal remodeling processes why?

A

don’t want it getting resorbed with typical bone remodeling

49
Q

what is necrosis

A

cell death

50
Q

when would orthodontic tooth movement no longer be possible?

A

-when excessiev forces cause necrosis of ligament by cutting off the normal blood supply to the cells

51
Q

can accidentally exfolliated teeth be replatned? complications?

A

yes

*complication are external root resorption and ankylosis if portion of the ligament are permanently damages

52
Q

what is the mean width of PDL at coronal end of alveolus?

A
  • premolar in heavy function= 0.35mm

* light function= 0.14

53
Q

what is the mean width of PDL in middle of alveolus?

A
  • premolar in heavy function= 0.28

* light function= 0.10

54
Q

what is the mean width of PDL iat apical end of alveolus?

A

is somewhere between coronal end and middle

Embryology (12 decks)

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