PDL

Question 1

average width of PDL

Answer 1

about .15-.4 mm and is considered to be about a quarter of a millimeter
thinnest at the mid-radiular aspect of the tooth. - hourglass shape.
decreases with age of patient by about .05-.10 mm

Question 2

PDL two components

Answer 2

extracellular fibers - ECM/matrix - the ligament connecting part
Cells - the maintenance or regeneration aspect. comprised of fibroblasts and neurovascular elements

Question 3

height of PDL

Answer 3

coincides with the height of the cribriform plate of alveolar bone
Approx. 1-2 mm apical to CEJ
CEJ–> crest of bone about 1-22 mm

Question 4

three main functions of the PDL

Answer 4

Attachment - via the tensile strength components
Adaption - via the viscoelastic components (withstand the forces and bruxism +nocturnal grinding)
Sensory perception - via the nerves - properly position teeth during chewing and withstand forces

Question 5

Rheologic Principle

Answer 5

fluids under pressure are incompressible - application of force on tooth displaces fluids either through the foramina of the cribriform plate or onto other PDL regions - causes dilation / widening of the socket due to fluid displacement

abnormal widening of PDL seen on radiographs - significant marker for occlusal overload?

Question 6

collagen fiber groups in PDL (from CEJ to apical)

Answer 6

alveolar crest 
horizontal
oblique
apical 
interradicular group

Question 7

alveolar crest group

Answer 7

attach to cementum 1-2 mm apical to CEJ - run apically in an oblique direction toward the alveolar bone
insert into the coronal crest of aveolar bone

Question 8

lateral periodontal cyst

Answer 8

from the HERS and the Rest cells of M. - could result in this and lead to a translucent in a radiograph - by the activaiton of the rests cells

Question 9

immature elastic fiber variants

Answer 9

in the PDL - and because they are immature result in the dynamic aspects of the PDL
examples - oxytalin and Elaunin

Question 10

oxytalin and elaunin

Answer 10

immature elastic fiber variants

Question 11

dermatan sulfate

Answer 11

main proteoglycan / glycosaminoglycan in the PDL

Question 12

% of water in pdl and reason

Answer 12

70% - due to the viscoelastic feature of the PDL (also why we have immature elastin)

Question 13

what does the PDL develop from?

Answer 13

From the dental follicle - sometimes referred to as the sac

-originally derived from ectomesenchymal cells from neural crest cells

Question 14

importance of lysyl oxidase?

Answer 14

needed for collagen biosynthesis - lysyl oxidase dependent cross linking

Question 15

changes in alveolar crest fibers as tooth errupts

Answer 15

first oblique –> horizontal–> then oblique the other way (inserting into the coronal crest)

Question 16

hyperfunction in PDL

Answer 16

due to traumatic occlusion and leads to widening of the PDL
- primarily due to fluid displacement and results in not only widening of the PDL but also the collagen fibers and the bone
- increasing width of PDL
can see this radiographically and histologically

Question 17

tooth avulsion

Answer 17

• means pulling or tearing away

- reattachment of PDL can occur in two ways - ankylosis or by gomphosis

Question 18

reattchment of PDL in tooth alvulsion - two mechanisms

Answer 18

ankylosis - if there is NO source dental follicle cells - basically the bones fusing
gomphosis - if there IS A SOURCE DENTAL FOLLICLE CELLS

Question 19

guided tissue regeneration

Answer 19

selective re-population by PDL cells via use of a PHYSICAL barrier that excludes gingival fibroblasts and epithelial cells - trying to get back CELLULAR CEMENTUM FORMATION??

Question 20

Emdogain

Answer 20

mimics the embryologic development events via use of enamel protiens
trying to get back ACELLULAR CEMENTUM FORMATION?? - main cementum for attachment

Question 21

hyalinization

Answer 21

the light microscopy term for trauma-induced acellularity of the PDL

Question 22

which fibers are believed to provide the mechanism for eruptive tooth movement and also for the phenomenom of vertical drift?

Answer 22

OBLIQUE fibers

Question 23

mesial drift?

Answer 23

due to the transseptal fibers of the gingiva - anterior component of occlusal forces