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