PAP 1 - The periodontium anatomy and function Flashcards
What does the periodontium mean?
“Around the tooth”
what 4 (3) major structures is the periodontium comprised of?
- Gingiva
- Periodontal ligament
- alveolar bone
- Cementum (sometimes not included)
What is the function of the periodontium?
- Attachment of teeth to the jaws.
* Effective support during masticatory function ( transport forces through teeth to dissipate it)
What are the 2 parts of the gingiva?
- free gingiva
- attached gingiva
where is the free gingiva found?
coronal to the epithelial attachment
where is the attached gingiva found?
tightly bound to the underlying bone = muco-periosteum
what is the function of the gingiva?
- Provides attachment between the oral mucosa membrane and the teeth
- Prevents bacterial invasion of the underlying periodontal tissues
Where is the gingiva attached in health?
Attached to the teeth at or just coronal (above) to the Amelo-Cemental Junction (ACJ)
What does the gingiva comprise of?
- fibrous connective tissue covered by epithelium
- extends from mucogingival junction to the tooth surface
Describe gingival health.
- Firm.
- Pale pink.
- Stippling of the attached gingiva: orange peel appearance
- Interdental papillae fill space under tooth contacts.
- No bleeding on probing (BOP).
In pristine gingival health, what do you see?
Gingival groove: junction between the free and attached gingiva
What is the part of the gingiva between the teeth?
interdental papilla
In health, what does the interdental papilla look like?
triangular/pyramidal in shape -
Describe the contact point.
The contact point between immediately adjacent
incisors is narrow. Between molars it is broader
what is the Col?
Where the buccal & lingual papillae meet interdentally
(premolars/molars) and this is below the contact point
What problems arise at the Col?
• Covered in non-keratinised epithelium.
• Difficult to clean – interdental cleaning.
• Fragile blood supply – at the junction between the
buccal & lingual microvessels.
• Therefore the col is an area is very prone to periodontal
inflammation & disease progression
what is the basic structure of the oral epithelium?
Stratified squamous epithelium
What 2 groups of cells compose the oral epithelium ?
- Keratinocytes (90%)
- Non-keratinocytes
Name 4 types of non-keratinocytes -clear cells.
- Langerhans cells (involved in defence - antigen presenting cells)
- Melanocytes (produce the pigment melanin)
- Lymphocytes (immune).
- Merkel cells (slowly adapting sensory touch receptors)
In keratinised sites , what are the 4 layers histologically?
- Basal cell layer (stratum basale/ germinativum)
- Prickle cell Layer (stratum spinosum)
- Granular cell layer (stratum granulosum)
- Keratinized layer (stratum corneum)
Where does cell division of epithelium occur?
- Cell division basal cell layer.
* Cells tend to move through the epithelium towards the surface - shed.
During the cell division, what happens to the cells?
Cells increase in size + become more flattened + keratin is produced
what does the process of the cells changing their shape do?
- This process packs cells together in the keratinized layer.
- Creates a mechanically tough outer surface
What is this maturation of the cells called?
Differentiation
Give an example of non-keratinizng epithelium?
Alveolar mucosa
what is less marked in non-keratnized epithelium?
changes in the keratinocytes
what layers are absent in non-keratinised epithelium?
Granular & keratinized layers are absent
What is the granular layer replaced with in non-keratnisied epithelium?
Intermediate layer
What is the keratinised layer replaced with in non-keratnisied epithelium?
surface layer
Why is alveolar mucosa more red?
so the blood shines throguh as blod vessels are close to surface
what is synthesised during epithelial differentiation and in what layers?
Membrane Coating Granules (MCG) are synthesized in the prickle & granular cell layers
What do membrane coating granules contain?
lipids which are discharged into intercellular spaces in both keratinized & non-keratinized epithelium
What do these discharged lipids do?
- Forms a barrier to free permeability of water & water- soluble substances.
- Barrier incomplete & varies from site to site
What 3 regions is the gingival epithelium divided into?
- Oral gingival epithelium
- Oral sulcular epithelium
- Junctional epithelium
Where is the oral gingival epithelium found?
-Faces towards the oral cavity : attached gingiva + free gingiva
Where is the oral sulcular epithelium found?
Faces towards the tooth but not attached to it
Where is the junctional epithelium found?
In contact with the tooth
What is oral gingival epithelium?
Orthokeratinised - cells in the keratinised layer of thew epithelium are flattened and do not contain nuclei
Describe the appearance of the junction between the oral gingival epithelium and the underlying gingival connective tissue.
-“wavy” course as the tissues project into each other :
>connective tissue papillae
>rete pegs (epithelial ridges)
Describe the oral sulcular epithelium?
- Lines the gingival sulcus/crevice.
- Faces the tooth surface
- Non-keratinized
- Rapid turnover of epithelial cells to help shed attached bacteria in the gingival sulcus.
- Shallow rete-peg pattern.
Describe junctional epithelium .
- Forms epithelial attachment to the tooth.
- Non-keratinised.
- Hemi-desmosomes anchor basal keratinocytes to the basement membrane
what is found at the base of the sulcus?
Amelo-cemental junction
How is the junctional epithelium formed?
- Formed by fusion of the Reduced enamel epithelium with the Oral epithelium on tooth eruption.
- As the tooth reaches occlusion the attachment moves apically down the crown.
- Stabilizes near the Amelocemental junction (ACJ)
where does the junctional epithelium terminate?
coronally in the base of the gingival crevice
How are junctional epithelium cells orientated?
parallel to the tooth surface
What is the turnover of junctional epithelium?
JE rapidly turns over - every 4-11 days (mean = 5 days)
Where do cell divisions occur in the junctional epithelium and where do they shed?
- Cell divisions occurs throughout the JE.
* Cells shed into the gingival sulcus
what do a small number of neutrophils do in the junctional epithelium?
Small numbers of neutrophils pass through the JE to enter the gingival crevice (defence)
How is the differentiation of the junction epithelium and what does it not synthesise?
JE cells are poorly differentiated & do not synthetize membrane coating granules
What makes the junctional epithelium readily permeable?
large intercellular spaces making it readily permeable
what is found in the gingival connective tissue immediately adjacent to the junctional epithelium?
dense dentogingival plexus of blood vessels
What is produced from the post-capillary venues of the dentogingival plexus?
Gingival crevicular fluid (GCF)
Where does gingival crevicular fluid flow?
gingival crevice and into the mouth
-mixes into the salvia
How much gingival crevicular fluid is there when the mouth is healthy?
Very little GFC - as it is used to wash away bacteria and toxins
What does GCF contains?
Various components of blood and cells:
- various plasma proteins
- Defence cells/proteins
- Neutrophils (PMNs)
- Antibodies
- complement
when does volume/flow of GCF increase?
gingival / periodontal disease
what is the main components of the gingiva?
gingival connective tissue -highly vascular connective tissue
What are the 2 main components of gingival connective tissue?
- Collagen fibres (60% volume)
- extracellular matrix
what produces gingival connective tissue?
fibroblast
What cells types are found in gingival connective tissue?
•Fibroblasts (predominant). -spinde shaped or stellate cells -oval shaped nucleus •Macrophages -inflammtory defence cells •Polymorphs / Neutrophils -inflammatory defence cells •Lymphocytes & Plasma cells -defence cells
In gingival connective tissue, how are the collagen fibres arranged?
- Circular fibres (ring around tooth)
- Trans-septal fibres (embedded in the cementum of adjacent teeth)
- Dento-ginigval fibres
- Dento-periosteal fibres
- Crestal fibres
What do the college bundles do?
Attaches gingival tissues tooth and bone
where do crestal fibres go from?
Fan out from the crest of the alveolar bone into the attached gingiva
what is collagen in gingival connective tissue synthesised and degraded by?
gingival connective tissue fibroblasts:
- type I collagen most common in gingiva
- others found in gingiva are type III, IV and V
What is the extracellular matrix?
A complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells. Serves as a structural element in the tissues and also influences their development and physiology
what synthesises extracellular matrix?
fibroblasts
what role does extracellular matrix play?
important role in the regulation of cell behaviour
what does the extracellular include?
glycosaminoglycans (GAG) / proteoglycans / glycoproteins
what is the most common GAG?
hyaluronic acid
What are GAGs?
GAGs are negatively charged long unbranched polysaccharides:
- bind a lot of H20
- thus acts to resist compressive forces -hydrostatic cushion
what is a periodontal ligament?
-Specialised vascular connective tissue :
>continuous with the gingiva and pulp
>derived from the dental follicle
where is the periodontal ligament found?
- Fibrous attachment of the tooth (collagen).
* Inserts into root cementum one side & onto alveolar bone on the other
what are the functions of the periodontal ligament?
-Physical : >attachement of teeth to the jaws >absorption/ transmission of forces >roles in tooth movement -Tissue formation/ maintenance -Nutrition: >bone/cementum -Sensory : >mechanoreception/ touch/ reflexes >nociception / pain
Describe the variable width of the periodontal ligament?
- Ranges from 0.15mm to 0.38mm
- thinnest in the middle third of the tooth
- Progressively decrease in width with age
