gingival fiber and PDL Flashcards
functions of gingival fiber ligaments
Provide rigidity and density to the marginal gingiva
Act as a periosteum for the interproximal crestal alveolar bone
Provide one-half of the biologic width
Act as a protective barrier for the crestal alveolar bone against the spread of gingival inflammation
Inhibit the apical migration of the junctional epithelium
GFL fiber groups, how they connect
- Dentogingival- tooth to gingiva
- Dentoperiosteal- tooth to periosteum
- Alveologingival- gingiva to alveolar bone
- Circular- surrounds tooth
- Transseptal- between teeth (MD)
- Semicircular- like a sling for the tooth
- Transgingival- from B to L papilla
GFL fibers labeled
GFL fiber labeled
biological width
The biological width is the area of junctional epithelium
and gingival fiber ligament attached to the root of a
tooth. Thus, the biological width extends from the most
coronal attachment of the junctional epithelium to the
crestal alveolar bone.
junc epithelium= 0.98mm
GFL= 1.02mm
violation of biological width
Violation of the biological width due to placement of
overextended restoration margins (subgingivally) will result in chronic
inflammation and, given sufficient time, induce loss of
supporting alveolar bone with formation of a diseased
periodontal pocket.
functions of PDL
Supportive Regenerative (possess undiff cells) Nutritional (possess blood supply) Sensory (ruffini/nocieption) Protective
PDL development
The PDL is derived from the ectomesenchymal cells (neural crest) in the intermediate zone of the dental follicle.
Cells in the most peripheral zone (outer) of the dental follicle give rise to the alveolar bone proper and those in the most proximal (inner) give rise to cementoblasts.
PDL assistance with eruption
form along with the tooth
will contract to assist with eruption
embedding of PDL fibers
collagen fibers grow from both the cementum and alveolar bone and branch
will interlock with one another to form the PDL
grow from principle fibers/ sharpey’s fibers
insertion of PDL in cementum: SEM
what supports the PDL?
The indifferent fiber plexus (arrows) consists of small diameter collagen fibers in random orientation that provide support for the sharpey’s fibers
cells of the PDL
Fibroblasts Osteoblasts Cementoblasts Macrophages Undifferentiated mesenchymal cells Endothelial cells Epithelial cells
PDL fiber groups labeled
Alveolar Crest
(pink arrow)
Horizontal
(greenarrow)
Oblique
Apical
Interradicular (only on multirooted teeth)cross section of PDL reveal
These x-sectional views of the PDL show the
arrangement of fibers that resist torque-like force
on the tooth.
ALL WORK TOGETHER TO RESIST ROTATIONAL FORCES
all PDL fibers tend to resist?
All PDL fiber groups tend to resist rotational forces
PDL Fiber Group Function Apical
Resist vertical force
PDL Fiber Group Oblique
Resist intrusive force
PDL Fiber Group Horizontal
Resist horizontal & tipping force
PDL Fiber Group Alveolar Crest
Resist vertical force
PDL Fiber Group Interradicular
Resist vertical & lateral force
GFL Fiber Group Transseptal
Resist tooth separation
GFL Fiber Group Dentogingival
Resist gingival displacemen
GFL Fiber Group Alveologingival
Resist gingival displacemen
GFL Fiber Group Circumferential
Resist gingival displacement
GFL Fiber Group Semicircular
Resist gingival displacement
& tooth separation
orthodontic relapse, fibers that contribute
PDL fibers possess memory> can relapse to original form after treatment
Transseptal Fibers (GFL)
Semicircular Fibers (GFL)
PDL Principle Fiber Groups
interstitial spaces of PDL, can provide?
Spaces around the blood vessels of the PDL
The PDL interstitial spaces are a source of mesenchymal cells that can differentiate into:
cementoblasts, osteoblasts, fibroblasts
Cementoblasts
- Regeneration and repair of cementum following injury
* Continuous physiologic deposition of cementum
Osteoblasts
• Continuous physiologic remodeling of supporting alveolar
bone
• Regeneration and repair of bone following orthodontic
therapy or disease
Fibroblasts
• Various phenotypes of fibroblasts are involved in collagen
production and physiologic collagen degradatio
PDL ankylosis
causes?
severity?
Fusion of cementum directly with the surrounding alveolar bone, without the intervening PDL
This is usually a reparative response to PDL injury
The degree of injury, and the type of cells that respond dictate the type of response
if the injury is significant, and the cells that respond
are from the surrounding alveolar bone, the result will be ankylosis (cementum fuses with alveolar bone)> intersitial spaces destroyed
if the injury is slight, and the responding cells are from themmPDL (i.e. undifferentiated cells), these cells have the potential to regenerate all tissues involved in tooth support, and the PDL will be restored> intersitial space not destroyed
ankylosis mechanism
initially macrophages and undiff cells enter the site of injury, macro will clear debris and undiff cells can become fibroblasts
PMN response=inflam, clear damaged tissue
depending on serveity PDL will then be regen or ankylosis will occur
ankylosis can complicate what?
extractions
PDL role in wound healing steps
The wound healing response is similar to the trauma response of the PDL.
- Undifferentiated cells migrate into the area, as macrophages and PMN’s remove damaged
tissues. - 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 the necessary cells reach their target.
basis of bone scraping/GTR
bone scrapping
can induce trauma to bone in attempt to induce bone formation> will cause macrophages and undiff cells to invade the space and lead to formation of granulation tissue and eventually bone
used to correct perio defects
guided tissue regen
A surgical technique of regenerating the periodontal attachment apparatus on periodontally involved teeth, which uses the differentiation of mesenchymal cells in the interstitial spaces of the PDL and marrow spaces of adjacent alveolar bone.
The membrane excludes gingival epithelial tissues from the deeper part of the wound,
and allows only cells from the existing PDL to repopulate the wound (promotes PDL/bone regen)
reflect tissue and scrape bone to induce this process, but also include the membrane
epithelial rests of malassez, activation/treatment?
most prevalent area?c
Remains of Hertwig’s root sheath – duct-like appearance Purpose is unknown
More prevalent in the apical areas of adolescents May have some effect on cementogenisis
if activated can form lateral periodontal cysts, appear radiolucent
treated with surgical removal
lateral periodontal cysts
treatment?
The lateral periodontal cyst typically occurs along the lateral root surface. It is believed to arise from epithelial rests (epithelial rest of Malassez in the PDL), when \stimulated. Treatment consists of surgical removal.
gingival cyst/ERS
may be correlated with?
The gingival cyst is derived from odontogenic epithelium located in the connective tissues of the gingiva known as the epithelial rests of Serres.
ERS are remnants of dental lamina
may be correlated to OKC
Orthodontic movement
Orthodontic tooth movement results in compression of the PDL on the side of the root corresponding to the direction of movement. Compression of the PDL results in loss of principle fiber orientation and resorption of adjacent bone.
The PDL on the tooth root opposite the compression side is characterized by tension or stretching of the PDL principle fibers. Controlled tension results in bone apposition (growth)
PDL trauma from occlusion
excessive functional stresses placed on a tooth by an antagonist (or removable prosthesis)
that exceeds the limits of physiologic adaptation.
• Resorption of alveolar bone parallel to the long axis of the root
• A PDL that is wider than normal average width (i.e., > 0.17 mm in
adult)
• Tooth mobility
disuse atrophy of PDL
A tooth with no occlusal antagonist will exhibit:
• A significant decrease in density of bony trabeculae
• Decreased width of the PDL (< 0.17 mm)
• Loss of orientation of the principle fibers of the PDL
• Increased volume of the bone marrow spaces
