periodontal ligament 1
DESCRIPTION
a fully packed ppt on the periodontal ligamentTRANSCRIPT
Periodontal LigamentPeriodontal Ligament
Introduction
Soft fibrous specialised connective tissue present in periodontal space b/w cementum of root & bone forming the socket wall
Other names Gomphosis Desmodent Pericementum Dental Periosteum Alveo-dental ligament Periodontal membrane
Is the dense, fibrous connective tissue ...
Average width is 0.2mmNonfunctional,unerupted Heavy occlusal stressHour-glass shapedWidest cervically
Evolution
Reptiles teeth are ankylosed to bone & growth is by sutures
Mammals teeth are suspended by ligaments in sockets & growth is by cartilage
Hertwigs Epith Root Sheath
Epithelial Rests of Malassez
Cells of dental follicle migrate to root dentin
Migrated follicular cells – cementoblast lay cementum
Other cells of dental follicle differentiate into fibroblast, synthesize fibers & extra cellular
substance of PL
Dental follicle cells
CONSTITUENTS OF THE PDL…..
1.Fibres 2.Ground
substance3.Cells 4.Blood
vessels 5.Nerves6.lymphatics
PRINCIPAL FIBERS -
Primarily composed of type I collagen fibrils.
Also contains oxytalan fibers -related to the microfibrillar component of elastic fibers.
Principal fibers of the PDL
Alveolar crest groupHorizontal groupOblique groupApical groupInterradicular group
ALVEOLAR CREST FIBRES-
HORIZONTAL FIBERS -
OBLIQUE FIBRES -
APICAL FIBERS -
INTER RADICULAR FIBRES -
TRANSEPTAL FIBRES -
•Do not have osseous attachment•Run from cementum to cementum•Reconstructed even after destruction
Arrangement of principle fibres –
Previously –
Fibres embedded in bone intercalated with fibres from cementum
Recent evidence – fibres cross entire width but en route branch & join adjacent fibre
Intermediate plexus –
Randomly arranged
SHARPEYS FIBRES -
ELASTIC FIBRE SYSTEM
FIBRES OF THE PDL -
FIBRES & CELLS OF THE PDL….
collagen
These are principal fibres of the periodontal ligament.
Type1 & type 3 collagen are present.They are high molecular weight protein
attached to small number of sugars & glycoproteins.
They are rod like & arranged in the form of bundles or fibres.
Oxytalan fibres
These are elastic fibres found in the PL They are restricted to the walls of the blood
vessels.They originate from cementun or bone & are
embedded into walls of the blood vessels.They support blood vessels in the PL.
CELLS OF THE PDL -
1.Fibroblasts2.Cementoblasts3.Cementoclasts4.Osteoblasts5.Osteoclasts6.Epithelial cell rests7.Defense cells –
macrophage leucocytes
lymphocytes mast cells plasma
cells
FIBROBLASTS-
Most numerous
65% of total cells
Densely packed population
Parallel to the collagen
fibres
Oriented along principal
fibresInterconnected by desmosomes. Nexus type junctions.
Prominent nucleus- flat, disc
shaped
Occupys 30% of cell space
Single distinct nucleolus
Clearly defined nuclear pores
Spindles / flat disks
Long ovoid nuclei, numerous
Cytoplasmic processes
Mitochondria – numerous, well
distributed
Lysosomes – large , membrane
bound vesicles
CEMENTOBLASTS & CLASTS -
Only observed during phases of active cementum deposition Oval to cuboidal shape Basophilic due to high % membrane bound and free ribosomes Easy to recognize, even under the light microscope Cementoblasts lining the cementum- plump cells, rich in cytoplasm Squat, cuboidal cells with large nuclei Structure – depends on activity
CEMENTOBLASTS & CLASTS -
Only observed during phases of active cementum deposition Oval to cuboidal shape Basophilic due to high % membrane bound and free ribosomes Easy to recognize, even under the light microscope Cementoblasts lining the cementum- plump cells, rich in cytoplasm Squat, cuboidal cells with large nuclei Structure – depends on activity
OSTEOBLASTS -
Near bone surfaceForm a layer of
cuboidal cellsBasophilic cytoplasmProminent nucleusNumerous orgenellesGet incorporated as
osteocytes
OSTEOCLASTS - Seen adjacent to the bone surface Irregular distribution Appear only in active resorption / deposition Form a continuous layer lining the osteoid Located in Howships lacunae.Large & multinucleatedRuffled border, clear/annular zone
Progenitor cells
Other cells
Epithelial cell rests of mallasezMast cells macrophages
GROUND SUBSTANCE
They are present between cells & fibers of the PL.
They contain GAG ;hyaluronic acid & proteoglycan & glycoproteins like fibronectin & laminin.
They control fibrillogenesis & fiber orientation.
They transport food to cells & waste products from cells to blood vessels.
Glycoproteins
Fibronectin; this is in filamentous form & promotes attachment of cells to collagen fibrils.it is involved in cell migration & orientation.
Tenascin; this glycoprotein is present adjacent to alveolar bone & cementum.
Interstitial tissue
Blood vessels,lymphatics & nerves of PL are surrounded by loose connective tissue which are called interstitial tissue
Structures present in the connective tissue
Blood vessels LymphaticsNervesCementicles
Blood vessels
The PL has rich vascular supply from superior & inferior alveolar arteries.
Blood vessels derived from; branches from apical vessels branches from intraalveolar vessels branches from gingival vessels
BLOOD SUPPLY -
Multiple supplyAverage diameter– 20υmGlomeruli-like arterio
venous shunts Veins- prominent beneath
JECirculus –Wong & Sims
1971
Lymphatics
The lymphatic drainage is from PL to the alveolar bone.they follow the path of blood vessels.
Nerve supply
Nerves pass through apical foramen to enter the PL.
Finer branches enter middle & cervical portions of the PL through openings in the alveolar bone
Types of nerves
Non myelinated nerves; they are autonomic nerves having a diameter of 0.5µm & supply blood vessels.
Myelinated nerves; they are sensory nerves having a diameter of 5µm.the sensation of pain,pressure & touch are felt by finer myelinated nerves & proprioception through larger myelinated nerves.
Free nerve endings –
sensory
More near cementum
For pain perception
Ruffini type endings –
mechanoceptors
Extraordinarily defined
pressure sensation
Coiled meissners- midroot region, mechanoceptors
Spindle-like endings – apex, surrounded by fibrous capsule
Cementicles
These are small calcified bodies present in the periodontal ligament.
They may remain free in the connective tissue or may fuse into large calcified mass.
They may be joined with cementum to form excementoses.
Degenerated epithelial cells form the nidus for their calcification.
CEMENTICLES
Functions of the PL
PhysicalFormativeNutritiveSensoryHomeostasis
Aging of the PL
As the aging occurs in the PL the number of cells & their activity decreases.
Scalloping occurs in the cementum & the alveolar bone.
There is increase in elastic fibers & decrease in vascularity,mitotic activity.
There is decrease in width & masticatory musculature strength.
Clinical considerations
Width of PL varies from 0.15-0.38mm,it decreases with age.
Gingivitis,Periodontitis.Trauma to ligament.Orthodontic tooth movement.Dental granuloma. Regeneration of PL.
GINGIVITIS,PERIODONTITIS
PERIODONTAL DISEASE
ORTHODONTIC TOOTH MOVEMENT
DENTAL GRANULOMA
PERIODONTAL REGENERATION
GTR
Guided tissue regeneration
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