periodontal ligament-summer
TRANSCRIPT
The PeriodontalThe Periodontal LigamentLigament
Dr. Khansa AbabnehDr. Khansa Ababneh
The Periodontal LigamentThe Periodontal LigamentThe PDL is the connective tissue that surrounds the root and attaches it to the alveolar bone
Continuous with the connective tissues of the gingiva and communicates with marrow spaces in bone
Physically small,
functionally important
PDLSubjected to continuous mechanical loading
High turnover rate
Embryonic-like tissue
PDLComposed of
1. Fibres
2. Cells
3. ECM
4. Nerves
5. Blood & lymphatic vessels
General Functions of PDL
Tooth support
Proprioception
Regulation of alveolar bone volume
Fibres
Most important are the principal fibres. Other fibres are oxytalan and eluanin fibres (immature elastic fibres).
Principal fibresType I and III collagen
Type I arranged in bundles
Follow a wavy course
Terminal portions inserted into cementum and bone are termed Sharpey’s fibres
Types V & VI collagen
Groups of fibresGroups of fibres
Transseptal groupConnect adjacent teeth
Alveolar crest groupResist extrusion, lateral movements
Horizontal groupResist lateral movements
Oblique groupReceive the bulk of vertical forces
Apical group
Resist intrusion & extrusion
Interradicular group Furcation areas of multirooted teeth
Formation of Principal FibresSharpey’s fibres start to form before cementum and
alveolar bone are mineralised.
Collagen Fibre BundlesCollagen Fibre Bundles
Sharpey’s fibresSharpey’s fibres
At insertion, PDL fibres are fully or partially mineralised
High levels of non-collagenous proteins , such as osteopontin
Cells
FibroblastsOsteoblastsCementoblastsDefence cells:macrophages, mast cells, eosinophils
OsteoclastsSensory cellsEpithelial rests of Malassez
Epithelial rests of Malassez
Interconnected Network
FibroblastsFormation & remodeling of PDL fibres
necessitates special signaling system
Different populations
(origin, protein sysnthesis; ALP)
ECM
CollagenCollagen
PGPG
Glycoproteins:Glycoproteins: fibronectin, tenascin, undulinfibronectin, tenascin, undulin
Growth factorsGrowth factors
CytokinesCytokines
Functions of PDL☻ Mechanical (physical)☻ Formative☻ Nutritive☻ Sensory
Physical Functions
Protection of vessels and nerves
Transmission of occlusal forces to bone (tension & compression)
Attachment of teeth to bone
Maintenance of gingival position
Shock absorption
Theories regarding mechanical function of the PDL
Tensional theory
Viscoelastic theory
Thixotropic theory
Force Transmission
Vertical forces
Horizontal or tipping forces
Axis of rotation
Hourglass shape of PDL
Shape & structure of PDL are adapted to its function
During normal functionDuring normal function
During orthodontic treatmentDuring orthodontic treatment
Normal Jiggling Forces
Widened PDLAdaptation
After Occlusal Adjustment