Pathology of Dental Caries Flashcards
What is enamel structure like?
Most highly mineralised extracellular matrix
Hard, thin, translucent layer
Vary in thickness and hardness
What is the problem with enamel?
Once enamel is gone it cannot be restored.
What is the chemical composition of enamel?
88% of inorganic mineral made of hydroxyapatite crystals.
2% of organic material/proteins
10% of water
Various ions strontium, magnesium, lead, fluoride
What is enamel composed of histologically?
Enamel rods
Perpendicular to dento-enamel junction (DEJ)
Run parallel from DEJ to surface
- 4 - 8 micrometers in diameter
Formed during amelogenesis
Clusters of small crystallites
What causes demineralisation and remineralisation to take place?
Demin:
Frequent carb intake
Frequent acid exposure
Plaque presence
Decreased salivary flow
Remin:
Exposure to fluoride
Removal of plaque
Balanced diet
Limited exposure to carbs
What are the zones of enamel caries?
Translucent zone
Dark zone
Body of the lesion
Surface zone
What happens in dentin following superficial enamel lesions?
Superficial enamel lesions
No reaction in the dentine and pulp in mature enamel
Dentinal reaction in immature enamel
What are the features of deep enamel lesions?
Dentinal reactions in immature enamel
Dentine tubules more obviously open to dyes and isotopes
Odontoblastic layer more obviously affected and even disrupted
What are the features of enamel caries with cavitation?
Irreversible
Reduced remineralisation potential
Organic destruction
What is dentine composed of?
It is porous and yellow-hued.
50% mineral, 25% organic matrix, and 25% water by weight.
Mineral content is mainly hydroxyapatite
Organic content mainly fibrous proteins, lipids, and non-collagenous matrix proteins.
How do dentinal tubules change as they get closer to the enamel? Why are they shaped this way?
Dentinal tubules at the pulp are numerous and wide open.
Diameter decreases towards the enamel.
They are shaped this way to allow superficial dentine to slow bacterial infiltration. If bacteria get near the pulp they invade the pulp rapidly.
What is the difference between infected and affected dentine?
Infected dentine:
Bacteria present
Collagen is irreversibly denatured
Not remineralizable and must be removed
Affected dentine:
No bacteria
Collagen is reversibly denatured
Remineralizable and should be preserved
What are the features of superficial dentinal lesions look like?
They are leathery clinically with few microorganisms and nutrients, they are anaerobic
Multiplication and metabolism is prohibited
Immature teeth (odontoblastic layer is affected, pulp-dentine membrane disrupted, and contains inflammatory cells)
What are the features of sclerosis?
Immediately located under the decalcified layer (reprecipitation of dissolved mineral)
Second layer acquires calcium through the pulp
Obstruction of dentinal tubules maintains a barrier
How does dental pulp respond to injury?
Large volume of tissue with a small volume of blood supply.
Terminal circulation with few collateral vessels and confined in calcified tissue walls.
A positive hydrostatic pressure is built up from the movement of proteins and minerals
Outward flow limits rate of diffusion of noxious agents (bacterial acids, metabolic products, cell wall components all of these diffuse pulpwards)
