OE L4 Dentine Structure Flashcards
Describe the composition of dentine.
- 70% inorganic: hydroxyapatite + small amounts of non-crystalline amorphous calcium phosphate
- 20% organic: 90% collagen + 10% lipids
- 10% water
Describe the physiology of dentine.
- Hard tissue
- Elastic properties due to tubular structure, supports brittle enamel
- Yellow
Circumpulpal dentine refers to…
Primary, secondary and predentine.
Doesn’t include predentine or tertiary dentine.
Describe mantle dentine.
First type of dentine formed, seen at outer edges and mineralised through matrix vesicles.
Describe primary dentine.
Refers to all of the dentine formed during tooth development. Includes mantle dentine and cirumpulpal dentine.
Describe secondary dentine.
Dentine laid down post eruption.
Made after root formation.
Odontoblasts continue to secrete dentine at a slow rate of 3-4microns a day.
Tubular structure.
Describe predentine.
The layer closest to pulp chamber (opposite of mantle dentine).
Unmineralised.
Secreted by odontoblasts as organic matrix, later remodelled to allow for mineralisation.
Describe tertiary dentine.
Formed in response to disease or trauma e.g. caries, abrasion. Aka. noxious stimuli.
Response is directly beneath region of disease or pathology.
Increases distance between noxious agent and pulp cells.
Divided into reactionary and reparative.
Describe reactionary dentine.
- Mild stimulus
- Pre-existing odontoblasts secrete dentine
Describe reparative dentine.
- Strong stimulus
- Odontoblasts killed and stem cell population recruited from pulp
- Odontoblast-like cells secrete a dysplastic dentine with irregular/no tubules
Also called osteodentine
Does pulp respond to restorative materials?
Yes.
Dental materials can trigger responses such as sensitivity, chronic inflammation and cellular toxicity.
This is because materials can leak through dentinal tubules and reach the pulp.
Describe the appearance of carious dentine.
Heavily stained brown with soft texture.
Bacteria demineralising the dentine can be visualised as dark staining lines in tubules under microscope, also note presence of demineralisation front.
What 2 types of curvature do dentinal tubules show?
Primary curvature- sigmoidal path of dentinal tubules due to crowding towards pulp
Secondary curvature- of the dentinal tubule walls themselves (wobbly)
Where are there more tubules, at the pulp or ADJ?
At the pulp (45,000/mm^2).
At enamel it is 20,000mm^2.
Consequences of branched tubules.
- Good for elasticity and nutrient supply
- However, not so good for caries development and response to restorative materials
