Periodontal Ligament Flashcards
What is the gingival fiber ligament?
ligament that attach crown of tooth to the periodontal ligamnet
What are the functions of the GFL?
-provide rigidity and density to marginal gingiva
-act as periosteum for interproximal crestal alveolar bone
-provide one half of the biologic width
-act as a protective barrier for crestal alveolar bone against the spread of gingival inflammation
-inhibit the apical migration of junctional epithelium
What are the GFL fiber groups?
-dentogingival
-dentoperiosteal
-alevologingival
-circular
-transeptal
-semicircular
-transgingival
What does the transgingival giber group do?
hold papillae intact between the teeth
What is the biological width?
area of junctional epithelium and gingival fiber ligamnet attached to the root of the tooth
-from crest of gingiva to crest of alveolar bone
What is the border of the biological width?
most coronal attachment of the junctional epithelium to the crestal alveolar bone
What is caused with violation of biological width
chronic inflammation and potential of loss of supporting alveolar bone
Where is the PDL compared to GFL ?
more apical on the tooth compared to the GFL
What are the functions of PDL?
supportive
regenerative
nutritional
sensory
protective
What allows the PDL to be regenerative?
has undifferentiated cells that are able to be activated and differentiae into different tissues
What is the PDL derived frm?
neural crest cells
What zone of the dental follicle does the PDL come from?
the intermediate zone
What do cells in the outer zone of the dental follicle form?
alveolar bone proper
What do cells in the inner zone of the dental follicle form?
cementoblasts
How does the PDL help with tooth eruption:?
as the PDL grows, fiber groups form
-these fiber groups will contract and coronally push the tooth into the mouth
How does the PDL develop?
the fibers form, the interlock with other groups of fibers and form a mesh work
-the collagen from the fibers then gets embedded into the cementum
What are sharpey’s fibers”?
fibers of PDL that are stuck into the cementum
What surrounds the principle fibers of PDL?
indifferent fiber plexus
-small diameter collagen fibers in random orientation
What cell types are in the PDL?
-fibroblasts
-osteoblasts
-cementoblasts
-macrophages
-undifferentiated mesenchymal cells
-endothelial cells
-epithelial cells
What are the fiber groups of the PDL
-alveolar crest
-horizontal
-oblique
-apical
-interradicular
What is the function of apical fiber group? PDL
resist vertical force
What is the function of oblique fiber group? PDL
resist intrusive force
What is the function of horizontal fiber group? PDL
resist horizontal and tipping forces
What is the function of alveolar crest fiber group?: PDL
resist vertical force
What is the function of interradicular fiber groups? PDL
resist vertical and lateral forcesWh
What is the overall function of the PDL fiber groups?
to resist rotational forces
What is the function of the transseptal fiber group? GFL
resist tooth separatio n
What is the function of the dentogingival fiber gorup? GFL
resist gingival displacementW
What is the function of the alveologingival fiber? GFL
resist gingival displacement
What is the function of the circumferential fiber group? GFL
resist gingival displacement
What is the function of the semicircular fiber group? GFL
resist gingival displacement and tooth separation
What can an orthodontist do to prevent tooth movement after original adjustment?
cut the ligament fibers to avoid moving back
(transseptal, semicircular, and PDL principle fiber groups)
What can the mesenchymal cells in the PDL interstital space differentiate into?
cementoblasts, osteoblasts, and fibroblastsd
What do cementoblasts do?
regenerate and repair cementum following injury
-continuous deposition of cementum
What do osteoblasts do?
-continuous remodeling of alveolar bone
-regeneration and repair of bone following orthodontic therapy or disease
What do fibroblasts do?
various are involved with making collagen
(help recreate the PDL if it has been damaged )
What is ankylosis?
fusion of cementum directly with the surrounding alveolar bone without the intervening PDL
When does anklyosis typically occur?
when there is some type of injury (significant)
-trying to repair the PDL
What are the steps in anklyosis?
-injury
-undifferentiated mesenchymal cells differnentiate into macrophages
macrophages eat the bad
-become fibroblasts
-PMN response (inflammatory)
-can either restore the PDL or lose the PDL and form bone
What is the role of PDL in wound healing? >
- undifferentiated cells migrate into the area, macrophages and PMN remove damaged tissue
- fibroblasts and/or osteoblasts replace the damaged tissue
- a mast cell response is usually present, in which heparin and histamine are released. this inflammatory response helps necessary cells reach their target
When there has been a disruption to the biological width, what can be done?
a flap can be cut into the gingiva
-some of the top layers of the ligament and bone can be disturbed
-this willl cause the activation of the mesechymal cells to fill in the area properly
What is guided tissue regeneration?
a procedure done to try and repair defects in the PDL and alevolar bone
-use a membrane that blocks epithelial tissue from migrating down into the pocket
-forces the mesenchymal cells of PDL to differentiate and fill the space
-done when the PDL and bone need to be regenerated
What is hertwigs root sheath formed from?
the fusion of IEE and OEE
What is a rest of malassez?
a clump of cells from hertwig’s root sheath that remains in the PDL
Where and who are Rests of Malassez most common?
more prevalent in apical areas of adolescents
What are lateral periodontal cysts ?
cysts that form when the Rests of Malassez become activated
-can tell on radiographs because you can see the PDL through the cysts
What are gingival cysts ?
cysts that form from epithelial rests of serres
-made form odontogenic epithelium
-could be connected to OKCs
What are rests of serres?
groups of cells that are remnants of the dental lamina
-made of odontoblasts
What does compression of the PDL cause ?
loss of principle fiber orientation and resorption of adjacent bone
What does stretching of the PDL cause?
results in bone appositon
-helps to ensure the tooth stays where it is moved to
What occurs to PDL with orthodontic treatment?
the PDL is stretched and compressed
-causes the moving of tooth
What is trauma from occlusion ?;
excessive functional stresses placed on a tooth by antagonist that exceeds the limit of physiological adaption
What are some of the effects of trauma from occlusion?
-resorption of alveolar bone parallel to the long axis of the tooth
-A PDL that is wider than normal average width
-tooth mobility
What is disuse atrophy
a tooth with no occlusal antagonist with exhibit
-decrease in density of trabecular bone
-decreased width of PDL
-loss of orientation of principle fibers of the PDL
-increased volume of bone marrow spaces
