Week 5 - Periodontal & Gingival Fiber Ligaments Flashcards
Where are gingival fiber ligaments located?
Coronally
What does the gingival fiber ligament do for the marginal gingiva?
Provide rigidty and density to the marginal gingiva
What does the gingival fiber ligament act as for the alveolar bone?
Periosteum (attachment zone) for the interproximal crestal alveolar bone
What width does the gingival fiber ligament provide?
One half of the biologic width
- 2mm barrier space between restoration and edge of pocket depth
What does the gingival fiber ligament do in terms of protection?
Protective barrier for the crestal alveolar bone against the spread of gingival inflammation apically
What does gingival fiber ligament inhibit?
The apical migration of the junctional epithelium
- to keep the pocket depth at a minimum
What are the fiber groups of the GFL?
- alveologingival
- circular (alveolar crest to gingival tissue)
- dentogingival (tooth to gingiva)
- dentoperiosteal (tooth to periosteum (alveolar crest))
- semicircular (stabilize buccal lingually)
- transseptal (tooth to tooth; keep stable mesiodistally)
- transgingival (buccal to lingual papilla to stay in tact)
What is the biological width?
The area of the junctional epithelium and gingival fiber ligament attached to the root of a tooth
Where does the biological width extend from?
The most coronal attachment of the junctional epithelium to the crestal alveolar bone
What does violation of the biological width due to placement of overextended restoration margins result in?
Chronic inflammation and induce loss of supporting alveolar bone with formation of a diseased periodontal pocket
- ‘body saying you are too close to the alveolar crest, i need that 2mm of space so back off’
Describe the measurements of the biological width
Junctional epithelium:
0.98mm
- Used in measuring pocket depth. Where probe is pushed down and cannot go farther
Gingival fiber ligaments:
1.02
= 2.00mm of biological width results
What happens if there is violation of the biologic width?
Chronic irritation and possibility to do crown lengthening
Where is the periodontal ligament?
More apical than GFL
What are the functions of the PDL?
- supportive (suspends tooth in socket)
- regenerative (undifferentiated cells for repair and cementum/bone repair)
- nutritional (blood vessels to deliver)
- sensory (tactile receptors)
- protective (cushioning tooth)
What cells if the PDL derived from?
Ectomesenchymal cells (neural crest) in the intermediate zone of the dental follicle
What do cells in the most peripheral zone (outer) of the dental follicle give rise to?
Alveolar bone proper
What do cells in the most proximal (inner) give rise to?
Cementoblasts
How does the PDL help with development?
As tooth grows, the PDL fibers contract and push tooth up into mouth
How is the PDL made?
Due to interlocking branches from both sides
- embedding of collagen fibers of the PDL into cementum
What are the embedding of collagen fibers of the PDL into cementum?
Sharpey’s fibers
What provides support for the principle fiber groups of the PDL?
Indifferent fiber plexus of small diameter collagen fibers in random orientations
What are resident cell populations of the PDL?
- fibroblasts (repair collagen)
- osteoblasts (repair bone)
- cementoblasts (repair cementum)
- macrophages (immune response, resorption)
- undifferentiated mesenchymal cells (backup to make mature cells)
- endothelial cells (line blood vessels)
- epithelial cells (come form gingiva)
What are the PDL fiber groups?
- alveolar crest
- horizontal
- oblique
- apical
- interradicular (in furications of multirooted teeth)
What do x-sectional views of the PDL show?
The arrangement of fibers that resist torque-like force on the tooth
What is the function of apical fiber groups?
Resist vertical force
What is the function of oblique fiber groups?
Resist intrusive force
What is the function of horizontal fiber groups?
Resist horizontal and tipping force
What is the function of alveolar crest fiber groups?
Resist vertical force
What is the function of interradicular fiber groups?
Resist vertical and lateral force
What do all PDL fiber groups together tend to resist?
Rotational forces
What is the function of transseptal fiber groups?
Resist tooth separation
What is the function of dentogingival fiber groups?
Resist gingival displacement
What is the function of alveologingival fiber groups?
Resist gingival displacement
What is the function of circumferential fiber groups?
Resist gingival displacement
What is the function of semicircular fiber groups?
Resist gingival displacement and tooth separation
What fibers can succumb to orthodontic relapse?
Transseptal fibers
Semicircular fibers
PDL principle fiber groups
What are interstitial spaces?
Areas centered around vascular spots
What are PDL interstitial spaces a soruce of?
Mesenchymal cells that can differentiate into cementoblasts, osteoblasts, and fibroblasts
What is the function of cementoblasts?
Regeneration and repair of cementum following injury
- continuous physiologic deposition of cementum
What is the function of osteoblasts?
Continuous physiologic remodeling of supporting alveolar bone
- Regeneration and repair of bone following orthodontic therapy or disease
What is the function of fibroblasts?
involved in collagen production and physiologic collagen degradation
What is ankylosis?
Fusion of cementum directly with the surrounding alveolar bone, without the intervening PDL
When do tissues use ankylosis?
As a reparative response to PDL injury
What dictates the type of response when using anyklosis?
Degree of injury and type of cells that respond
How do cells respond in a significant injury?
the cells that respond are from the surrounding alveolar bone, the result will be ankylosis
How do cells respond in a slight injury?
responding cells are from the PDL (i.e. undifferentiated cells), these cells have the potential to regenerate all tissues involved in tooth support, and the PDL will be restored
What are the steps of ankylosis injury repair?
- site of injury
- Undifferentiated mesenchymal cell
- Macrophages and fibroblasts
- PMN response (inflammatory reaction to remove damaged tissue)
- Restored PDL or loss of PDL depending on severity
What is the wound healing 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
How can the PDL be used in wound healing?
“Flap surgery”
- scrape bone so cells can come in and cause tissue to form when bleeds
How can PDL be used in guided tissue regeneration?
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
How does the membrane work in guided tissue regeneration?
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
- they want cells to grow up NOT down
What are epithelial rest cells of malassez?
Remains of hertwig’s root sheaths when some areas don’t fuse, duct like appearance
What is the purpose of epithelial rest cells of malassez?
Unknown purpose
Where are epithelial rests more prevelent?
In apical areas of adolescents
What may epithelial rests have an effect on?
Cementogenesis
What is a lateral periodontal cyst?
It is believed to arise from epithelial rests (epithelial rest of Malassez in the PDL), when stimulated
Where does a lateral periodontal cyst occur?
Along the lateral root surface
tx: surgical removal
What is the gingival cyst derived from?
Odontogenic epithelial when the epithelial rests of serres cells become active
Where is the gingival cyst?
Connective tissue of the gingiva known as the epithelial rests of Serres (remainders of dental lamina)
What is treatment for gingival cysts?
Surgical intervention
What does orthodontic tooth movement result in?
Compression of the PDL on the side of the root corresponding to the direction of movement
What does compression of the PDL result in?
loss of principle fiber orientation and resorption of adjacent bone
What is the PDL on the tooth root opposite the compression side characterized by?
tension or stretching of the PDL principle fibers
What does controlled tension result in?
Bone apposition
What is trauma from occlusion?
excessive functional stresses placed on a tooth by an antagonist (or removable prosthesis) that exceeds the limits of physiologic adaptation
What are examples of trauma from occlusion?
- 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
What is disuse atrophy?
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
