24. Gingiva and GDJ Flashcards
Define ‘gingiva’
part of oral mucosa that surrounds and is attached to teeth and alveolar bone
- continuum with oral mucosa and periodontal ligament
What creates the DGJ?
tooth eruption
How does tooth eruption create a DGJ?
- during tooth eruption, reduced enamel epithelium fuses with oral epithelium to establish dentogingival junction
- tooth approaches oral epithelium, only a thin layer of connective tissue separates the REE from oral epithelium (stratified squamous)
- fusion of REE with OE and degeneration of central epithelial cells
- epithelial continuity at all times (no connective tissue exposure - no bleeding)
- tooth erupted and DGJ formed - junctional epithelium are for tooth attachment
Immediately after tooth eruption, junctional epithelium is entirely …
- reduced enamel epithelium
- not keratinised and attaches firminly to enamel of teeth
What happens to epithelium some time after tooth eruption?
- gingival epithelium (is stratified, keratinised) appears to overgrow and replace REE
- sulcular epithelium then (statified, non keratinised)
- switch from gingival to sulcular keratinocyte identity and stratification of REE cells and rete peg formation
- development of sulcus induced by masticatory forces acting on gingiva
- base of sulcus is same level as free gingival groove
- junctional epithelium still appears like REE
What happens to gingival epithelium 2-3 years after tooth eruption?
- gingival ep appears to have completely replaced REE (based on epithelial morphology e.g stratified rete pegs
- small epithelial tag from REE remains - cell remnants and primary enamel cuticle (Nasmyth’s membrane)
Are junctional and gingival epithelial cells the same?
- molecular markers indicate no
- REE can become stratified and develop rete pegs
- stem cells can reform JE - tooth attachment restored after gingivectomy and gingival tissue grafting
Origin of junctional epithelium
-amelotin and odontogenic ameloblast-associated
- normally expressed by maturation stage ameloblasts - forming REE
- expression in internal basal lamina and junctional epithelial cells suggests junctional epithelium is derived from REE
How is there tight attachments of junctional epithelium to teeth?
- epithelial cells secrete primary enamel cuticle - internal basal lamina - onto enamel surface where it bonds with enamel proteins
- cells attach via hemidesmosomes
- external basal lamina (typical composition) attaches to lamina propria
- very strong epithelial attachment to tooth
- once lost in periodontal disease, it is difficult to regenerate
Junctional epithelium is … due to …
- permeable
- due to reduced number of desmosomes and larger intercellular spaces
- allows passage of gingival crevicular fluid and defence cells into sulcus
Gingival crevicular fluid contains …
- immunoglobulin molecules
- complement factors
- macrophages
- cytokines and metalloproteases (during infection)
- desquamated sulcular and junctional epithelial cells (around 5-6 days turnover)
What is the function of GCF?
- defence against pathogens
What if GCF is overproduced?
- tissue damage through overproduction of MMPs
- these degrade extracellular matrix and collagen fibres of gingival connective tissue
Composition of GCF can be measured and is an indicator of …
periodontal health
Gingival features and landmarks
- attached gingiva - tightly attached to tooth and alveolar bone
- alveolar mucosa - loosely attached to alveolar bone
- submucosa (of alveolar mucosa)
- free gingiva (not bound to other tissue)
- free gingival groove
- gingival margin
- gingival sulcus
- junctional epithelium
- sulcular (crevicular) epithelium
What is the mucogingival junction?
- boundary between alveolar mucosa (lining mucosa) - non-keratinised
- darker colour, more translucent revealing superficial blood vessels and attached gingiva (masticatory mucosa - parakeratinised or partially orthokeratinised)
- lighter colour shows characteristic ‘surface stipples’ in healthy gingiva
What makes up the attached gingiva?
- epithelium is thick and parakeratinised - becomes orthokeratinised
- lamina propria - long, narrrow papillae with dense collagen fibres
- mucoperiosteum (fibrous connection) instead of submucosa - provides stability to withstand forces of mastication
Clinical relevance of mucoperiosteum
- difficult to inject and painful for patient
- does not require suturing (in constract to lining mucosa)
The gingiva forms a mucoperiosteum. What does this mean?
- submucosa provides mobility and acts as a ‘cushion’ e.g in lining mucosa
- mucoperiosteum is where the lamina propria is more fibrous and directly joined with periosteum of bone e.g masticatory mucosa (middle of hard palate, gingiva)
List groups of gingival principle fibres
Which are seen in buccal/mesial view?
- transeptal - buccal
all below mesial - dentogingival
- alveogingival
- dentoperiosteal
- circular
Explain transseptal gingival fibres
- run interdentally from CEJ over alveolar crest to CEJ of neighbouring tooth
- fiber system that connects all teeth to jaw
- controls mesio-distal spacing
Clinical relevance of transseptal fiber group
- slow pace of remodelling even under mechanical stress
- can cause post-retention relapse of orthodontically repositioned teeth
Which is the largest and smallest group of gingival fibres?
- dentogingival
- circular
What do dentogingival fibres do?
- connect cervical cementum to lamina propria of free and attached gingiva
What do alveogingival fibres do?
- connect alveolar crest to lamina propria of free and attached gingiva
What do dentoperiosteal fibres do?
- run from cementum over outer surface of alveolar process and insert either into alveolar process or vestibular muscle/floor of mouth
What do circular fibres do?
- form band around neck of teeth and interlace with other fibres in free gingiva
- binds free gingiva to tooth
What causes gingivitis?
mild inflammation
Explain how mild inflammation causes gingivitis
- dental plaque accumulation causes inflammatory response in gingival connective tissue
- 70% of collagen fibres are destroyed within 3-4 days
What does treatment of gingivitis aim to do?
- stop spread of inflammation into periodontal tissues (PDL and bone)
Why is there abnormal wound healing in periodontitis?
- persistant inflammation causes further destruction of connective tissue by inflammatory cells
- causes apical migration of junctional epithelium
- formation of gingival pocket
- advanced cases show loss of PDL and alveolar bone
What is the mechanism of epithelial down growth?
- growth until intact connective tissue is reached
- compensation for loss of mechanical stability
How to prevent epithelial down growth in periodontal surgery?
- insertion of membrane (physical barrier)
- formation of fibrin clot against root surface
What is the main indicator of periodontal health?
depth of gingival sulcus
What is a healthy and diseased gingival sulcus?
- 0.5-2mm is healthy
- over 3mm is diseased (a periodontal pocket)
Is probing gingival sulcus accurate?
- generally overestimates anatomic sulcus/pocket depth
- probe usually penetrates into inflamed tissue
