24. Gingiva and GDJ

Question 1

Define ‘gingiva’

Answer 1

part of oral mucosa that surrounds and is attached to teeth and alveolar bone
- continuum with oral mucosa and periodontal ligament

Question 2

What creates the DGJ?

Answer 2

tooth eruption

Question 3

How does tooth eruption create a DGJ?

Answer 3

• 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

Question 4

Immediately after tooth eruption, junctional epithelium is entirely …

Answer 4

• reduced enamel epithelium
• not keratinised and attaches firminly to enamel of teeth

Question 5

What happens to epithelium some time after tooth eruption?

Answer 5

• 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

Question 6

What happens to gingival epithelium 2-3 years after tooth eruption?

Answer 6

• 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)

Question 7

Are junctional and gingival epithelial cells the same?

Answer 7

• 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

Question 8

Origin of junctional epithelium

Answer 8

-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

Question 9

How is there tight attachments of junctional epithelium to teeth?

Answer 9

• 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

Question 10

Junctional epithelium is … due to …

Answer 10

• permeable
• due to reduced number of desmosomes and larger intercellular spaces
• allows passage of gingival crevicular fluid and defence cells into sulcus

Question 11

Gingival crevicular fluid contains …

Answer 11

• immunoglobulin molecules
• complement factors
• macrophages
• cytokines and metalloproteases (during infection)
• desquamated sulcular and junctional epithelial cells (around 5-6 days turnover)

Question 12

What is the function of GCF?

Answer 12

• defence against pathogens

Question 13

What if GCF is overproduced?

Answer 13

• tissue damage through overproduction of MMPs
• these degrade extracellular matrix and collagen fibres of gingival connective tissue

Question 14

Composition of GCF can be measured and is an indicator of …

Answer 14

periodontal health

Question 15

Gingival features and landmarks

Answer 15

• 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

Question 16

What is the mucogingival junction?

Answer 16

• 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

Question 17

What makes up the attached gingiva?

Answer 17

• 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

Question 18

Clinical relevance of mucoperiosteum

Answer 18

• difficult to inject and painful for patient
• does not require suturing (in constract to lining mucosa)

Question 19

The gingiva forms a mucoperiosteum. What does this mean?

Answer 19

• 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)

Question 20

List groups of gingival principle fibres
Which are seen in buccal/mesial view?

Answer 20

• transeptal - buccal
  all below mesial
• dentogingival
• alveogingival
• dentoperiosteal
• circular

Question 21

Explain transseptal gingival fibres

Answer 21

• run interdentally from CEJ over alveolar crest to CEJ of neighbouring tooth
• fiber system that connects all teeth to jaw
• controls mesio-distal spacing

Question 22

Clinical relevance of transseptal fiber group

Answer 22

• slow pace of remodelling even under mechanical stress
• can cause post-retention relapse of orthodontically repositioned teeth

Question 23

Which is the largest and smallest group of gingival fibres?

Answer 23

• dentogingival
• circular

Question 24

What do dentogingival fibres do?

Answer 24

• connect cervical cementum to lamina propria of free and attached gingiva

Question 25

What do alveogingival fibres do?

Answer 25

• connect alveolar crest to lamina propria of free and attached gingiva

Question 26

What do dentoperiosteal fibres do?

Answer 26

• run from cementum over outer surface of alveolar process and insert either into alveolar process or vestibular muscle/floor of mouth

Question 27

What do circular fibres do?

Answer 27

• form band around neck of teeth and interlace with other fibres in free gingiva
• binds free gingiva to tooth

Question 29

What causes gingivitis?

Answer 29

mild inflammation

Question 30

Explain how mild inflammation causes gingivitis

Answer 30

• dental plaque accumulation causes inflammatory response in gingival connective tissue
• 70% of collagen fibres are destroyed within 3-4 days

Question 31

What does treatment of gingivitis aim to do?

Answer 31

• stop spread of inflammation into periodontal tissues (PDL and bone)

Question 32

Why is there abnormal wound healing in periodontitis?

Answer 32

• 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

Question 33

What is the mechanism of epithelial down growth?

Answer 33

• growth until intact connective tissue is reached
• compensation for loss of mechanical stability

Question 34

How to prevent epithelial down growth in periodontal surgery?

Answer 34

• insertion of membrane (physical barrier)
• formation of fibrin clot against root surface

Question 35

What is the main indicator of periodontal health?

Answer 35

depth of gingival sulcus

Question 36

What is a healthy and diseased gingival sulcus?

Answer 36

• 0.5-2mm is healthy
• over 3mm is diseased (a periodontal pocket)

Question 37

Is probing gingival sulcus accurate?

Answer 37

• generally overestimates anatomic sulcus/pocket depth
• probe usually penetrates into inflamed tissue