PDL Flashcards
average width of PDL
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
PDL two components
extracellular fibers - ECM/matrix - the ligament connecting part
Cells - the maintenance or regeneration aspect. comprised of fibroblasts and neurovascular elements
height of PDL
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
three main functions of the PDL
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
Rheologic Principle
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?
collagen fiber groups in PDL (from CEJ to apical)
alveolar crest horizontal oblique apical interradicular group
alveolar crest group
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
lateral periodontal cyst
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
immature elastic fiber variants
in the PDL - and because they are immature result in the dynamic aspects of the PDL
examples - oxytalin and Elaunin
oxytalin and elaunin
immature elastic fiber variants
dermatan sulfate
main proteoglycan / glycosaminoglycan in the PDL
% of water in pdl and reason
70% - due to the viscoelastic feature of the PDL (also why we have immature elastin)
what does the PDL develop from?
From the dental follicle - sometimes referred to as the sac
-originally derived from ectomesenchymal cells from neural crest cells
importance of lysyl oxidase?
needed for collagen biosynthesis - lysyl oxidase dependent cross linking
changes in alveolar crest fibers as tooth errupts
first oblique –> horizontal–> then oblique the other way (inserting into the coronal crest)
hyperfunction in PDL
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
tooth avulsion
- means pulling or tearing away
- reattachment of PDL can occur in two ways - ankylosis or by gomphosis
reattchment of PDL in tooth alvulsion - two mechanisms
ankylosis - if there is NO source dental follicle cells - basically the bones fusing
gomphosis - if there IS A SOURCE DENTAL FOLLICLE CELLS
guided tissue regeneration
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??
Emdogain
mimics the embryologic development events via use of enamel protiens
trying to get back ACELLULAR CEMENTUM FORMATION?? - main cementum for attachment
hyalinization
the light microscopy term for trauma-induced acellularity of the PDL
which fibers are believed to provide the mechanism for eruptive tooth movement and also for the phenomenom of vertical drift?
OBLIQUE fibers
mesial drift?
due to the transseptal fibers of the gingiva - anterior component of occlusal forces
