The Periodontal Ligament Flashcards
What are the principle four components of the periodontium?
Alveolar bone Cementum Gingiva PDL These structures function as a unit, if one of them is damaged the whole unit itself is also weakened.
Why is the PDL important?
It is important b/c it is like a shock absorber during mastication. It connects the tooth to the alveolar bone.
It also contains many fibers and is mostly composed of Collagen Type I fibers.
What is ground substance? From the definition you should be able to note why ground substance is so important, and why it would be located in the PDL.
The ‘ground substance’ of extracellular matrix is an amorphous gelatinous material. It is transparent, colourless, and fills the spaces between fibres and cells. It actually consists of large molecules called glycosoaminoglycans (GAGs) which link together to form even larger molecules called proteoglycans. These molecules are very good at absorbing water, rather like a sponge, such that 90% of the extracellular matrix is made up of water. This means that the ECM is very good at resisting compressive forces.
PDL
Highly vascular and complex connective tissue
Surrounds the tooth root and connects it to the alveolar bone.
Mean width is 0.2mm
Name the principle fibers of the PDL. Collagen Type I.
Transseptal Alveolar crest Horizontal Oblique Apical Interradicular
What are Sharpey’s Fibers?
These fibers insert into the cementum and alveolar bone. Once these fibers become embedded in the cementum and alveolar bone they calcify.
The site of insertion of Sharpey’s fibers in alveolar bone proper is termed?
Bundle bone.
Bundle bone exhibits multiple perforations due to the penetration of Sharpey’s fibers.
Transseptal Fibers (Principle fiber of PDL)
These fibers extend interdentally between adjacent teeth (cementum to cementum).
They are especially important in maintaining the health of the dental arch.
Transseptal Fibers (Principle fiber of PDL)
Cementum to Cementum
There is no osseous attachment
Alveolar Crest Principle FIbers of PDL
These fibers extend obliquely from the cervical portion of the root cementum just apical to the junctional epithelium to the alveolar crest.
Alveolar Crest principle fibers are important to prevent what?
Alveolar crest fibers prevent EXTRUSION and lateral movement of the teeth.
Horizontal Principle PDL fibers
These fibers extend at right angles to the long axis of the tooth from the cementum to the alveolar bone.
Oblique Principle FIbers
Largest group of fibers, extend from cementum in a coronal direction obliquely to the bone.
Oblique fibers are important b/c why?
They bear the brunt of vertical masticatory forces.
Apical Principle Fibers
These fibers radiate irregularly from cementum to the bone at the apical region of the socket. They are found ONLY on teeth whose roots are completely formed.
Interradicular Principle Fibers
These fibers fan out from the cementum to the tooth in the furctation areas of MULTI-ROOTED teeth.
Why are interradicular fibers important?
Interradicular fibers are important b/c they resist NON-AXIALLY directed occlusal forces.
Furcation involvement is associated with the destruction of these fibers, either from perio disease or occlusal trauma.
What amino acids are associated with the PDL?
Hydroxylysine, hydroxyproline, glycine, and proline. Type I Collagen is produced by fibroblasts
Structure and composition of the PDL includes
Type I Collagen is produced by fibroblasts
Type III collagen
Oxytalan and elaunin (immature elastin fibers)
Why are oxytalan fibers important?
these immature elastin fibers regulate blood flow
Why is fibronectin important?
it is a glycoprotein for periodontal ligament collagen attachment to the tooth surface. Secreted by fibroblasts found within ground substance of PDL.
What are Cell Rests of Malassez?
They are remnants of Hertwig’s Epi Root Sheath
Can calcify to from cementicles
Can proliferate to form lateral periodontal cyst or periapical cyst
Cell Rests of Malassez can proliferate to cause what?
Lateral Periodontal Cyst
Periapical cyst
What is a cyst?
A cyst is a sac-like pocket of membranous tissue that contains fluid, air, or other substances. Cysts can grow almost anywhere in your body or under your skin. There are many different types of cysts. Most cysts are benign, or noncancerous.
Why is it important to have some much H2O in the PDL?
The PDL contains a high content of water because of the physical-chemical water binding properties of GAGs and glycoproteins contained within ground substance.
Heavy compressive force decreases water binding by disaggregating the GAGs and glycoproteins, resulting in PDL collagen fiber bundle compression, and emptying of blood vessels.
PREVENTS STRUCTURAL DAMAGE TO THE BONE AND LIGAMENT.
List 5 functions of the PDL?
Attachement of cementum to bone Protection Nerve transmission Resistance to impact of occlusal forces Formative and Remodeling Nutritional and Sensory
Tensional Theory , what does it describe?
Describes principal fibers of PDL transmitting occulsal forces to bone.
Viscoelastic System theory, what does it describe?
Not only are the principle fibers involved, but cells in the ECM have cells that help with dissipating occlusal forces. Main occlusal forces are displaced into the cells of the ECM.
The PDL has Meissner corpuscles that do what?
Involved with tactile light touch
The PDL has Ruffini mechanoreceptors that do what?
Respond to pressure and vibration
