Periodontium Flashcards
What is the periodontium
Tissues surrounding and supporting the teeth
What is the purpose of the periodontium
Retain tooth in socket
Resist masticatory loads
Defensive barrier, protecting tissues against threats from the oral environment
What separates the body tissues from the oral environment
Junctional epithelium
What are the two divisions of periodontal diseases
Diseases of the gingiva alone
Diseases of all the periodontal tissues
What are the periodontal tissues
Cementum
Gingiva
Periodontal ligament
Alveolar bone
What are the properties of cementum
Covers root dentine
Very similar in structure to bone
-Collagen matrix
-Lamellar arrangement
Provides attachment for some periodontal fibres
Two types:
-Cellular cementum
-Acellular cementum
Laid down by cementocytes
What makes cementum
Cementocytes
What is the differnece between acellular and cellular cementum
Acellular cementum
-No cells within
-Usually adjacent to dentine
-First formed (primary cementum)
Cellular cementum
-Contains cementocytes
-Later formed (secondary cementum)
-Present in apical part of root and in furcation regions
What happens to alveolar bone when teeth are lost
The alveolar process is resorbed leaving the ‘residual ridge’
What is the periodontal ligament
A connective tissue containing cells, extracellular matrix, fibres, nerves and blood vessels
What makes up the PDL matrix (ground substance)
Hyaluronate GAGs
Glycoproteins
-Fibronectin
Proteoglycans
-proteodermatan sulphate
-chondroitin/dermatan SO4 hybrid
What behaves like a viscoelastic gel
Ground substance
What cells are found in the PDL
Fibroblasts
Cementoblasts
Osteoclasts & Cementoclasts
Epithelial cells (cell rests of malassez)
Defence cells
What is the breakdown of the nerves within the PDL
Sensory
-Mechanoreceptors (A and Aδ fibres)
Rapidly or slowly adapting
Proprioception; chewing control
-Nociceptors (Aδ and C fibres)
Protective reflexes;
inhibit jaw elevator motor neurons
Autonomic (sympathetic)
-blood vessels control - vasoconstriction
What is the blood supply of the PDL
From inferior and superior alveolar arteries, passing into PDL from alveolar bone
From lingual and palatine arteries, supplying gingivae
What is the ‘gingival’ ligament
Fibres mainly above the alveolar crest, including ‘free gingival’ fibres
What does the periodontal ligament do
Attaches tooth to jaw
Transmits biting forces to alveolar bone
Organised (regular) connective tissue
Width of PDL is approx. 0.2mm
What is the approx width of the PDL
0.2mm
What fibres are present in the PDL
Collagen (type 1,3), support tooth
Oxytalan
Elastic (absent in humans)
What are the principle PDL fibre groups
Alveolo-dental ligament:
-Alveolar crest
-Horizontal
-Oblique
-Apical
-Interradicular (multi-rooted teeth)
Interdental ligament
-Transseptal fibres
What fibre groups are within the gingival ligament
Circular
Alveolo-gingival
Dento-periosteal (dashed)
Dento-gingival
What are intrusive forces
Mastication
Swallowing
Speech
What are extrusive and horizontal forces
Sticky foods, orthodontic forces
In which direction do the principal oblique fibres lie, relative to the alveolar bone and cementum?
They attach to the cementum apically and to the bone cervically
What is the main protein in the principal (Sharpey’s) fibres?
Collagen I,III
In which part of the root the cementum is thicker?
Apical region
Are oblique fibres wavy or straight
Wavy
What cells lie in the cementum surface?
Cementocytes
On which side of the periodontal ligament are the Sharpey fibres bundled more closely?
They are bundled closely at the cementum and spread at the bone
What are the epithelial cells found in periodontal ligament known to be the cause of?
Periapaical cyst
What is the difference between a cyst and a granuloma
Cyst moves tooth, granuloma engulfs tooth
Why is a periapical cyst odontogenic
Related to odontogenic material (debree of malassez) used to form a tooth.
What is a col
Region between two anterior teeth
non-keratinised,
