Instigated by the action of bacteria upon fermentable carbohydrates in the plaque biofilm on tooth surfaces.
Leading to acid demineralisation and proteolytic destruction of the organic component of dental tissues.
Define primary caries.
The process and lesion
Occuring on a previously sound tooth surface.
Where is primary caries found?
On a previously sound tooth surface.
Define root caries.
Primary caries
On an exposed root surface
Usually after gingival recession
Often leads to more easy penetration into exposed dentine.
Where does recurrent caries occur?
Margin of a restoration.
What is the carious process and what is its initial form?
The metabolic activity in the plaque biofilm on tooth surface.
It is initially adsorbed as the acquired pellicle.
What does the acquired pellicle consist of?
Salivary proteins and glycoproteins.
What causes a cariogenic environment in the carious process?
Increase in density of biofilm.
Increase in bacteria.
pH changes.
Oxygen tension.
Can the carious process be prevented?
No, the carious process cannot be prevented but it can be controlled so there is no clinically visible enamel lesion.
How can the cariogenic environment be controlled?
Inhibiting the demineralisation of enamel.
Encouraging the remineralisation process.
This can be done using a toothbrush and fluoride toothpaste.
This controls the environment but cannot prevent it.
How does a carious lesion form?
Due to metabolic activity within the biofilm.
Demineralisation is greater than remineralisation.
Can the carious lesion be prevented?
Yes, by regularly disturbing the tooth biofilm with a toothbrush and using fluoride toothpaste to help remineralise the tooth surface.
What 4 factors cause dental caries?
Bacteria in plaque
Susceptible tooth surface.
Fermentable carbohydrates.
Time.
What are the 4 stages in plaque formation?
Acquired pellicle formation
Pioneer microbial colonisers: the adherence of these to the acquired pellicle.
Co-aggregation: and enrichment of microbial species present.
Maturation: of dental plaque.
How is the acquired pellicle formed?
Acquired pellicle formation:
Salivary glycoproteins, phosphoproteins and lipids ADHERE to the enamel surface.
Low Molecular Weight (MW) proteins attach and then High MW proteins such as MUCINS attach.
These mucins ABSORB further proteins to form the pellicle.
What bacteria is the microbiological marker for caries, and how is its role described in the carious process?
Streptococcus mutans.
Associative role.
What 2 other bacteria are significant in the caries process?
Lactobacillus.
Bifidobacteria.
What is meant by a susceptible tooth surface?
Surfaces that have accumulated plaque and have stagnated.
Carious lesions are more prone to occur here.
Give 4 examples of susceptible tooth surfaces.
Depths of pits and fissures on posterior teeth (especially newly erupting molars).
Approximal surfaces (especially crowded teeth).
Smooth surfaces adjacent to the gingival margin.
Ledged/overhangs/defective margins of restorations.
How do plaque bacteria act on fermentable carbohydrates, and what does this cause?
Plaque bacteria metabolize certain dietary carbohydrates like sucrose and glucose.
This produces organic acids (lactic, acetic and propionic acids).
This causes plaque pH to fall within 1-3 minutes.
When the pH is 5.5, this is the critical pH, and this causes demineralisation to occur.
pH can take 60 mins to go back to normal.
What organic acids do plaque bacteria produce?
Lactic, acetic & propionic acids.
Why is time required to cause dental caries?
Sufficient time is needed for the plaque biofilm to produce a net mineral loss.
This equates to eventual hard tissue damage at the tooth surface.
What does the Stephan Curve show?
Changes in plaque pH over time after an oral glucose rinse at time 0 min.
Draw and label the Stephan Curve.
Oral glucose rinse at time 0 mins
What is the critical pH of enamel?
5.5
What is the critical pH of dentine?
6.2
How long does it take the pH to climb back to normal after falling below enamel critical pH?
The pH can take up to 60 minutes to climb back to normal, aided by the buffering capacity of saliva (pH 7).
How long does it take for the carious process to become clinically detectable and why?
Several weeks.
As the metabolic balance at the ion level is slow and can be moderated by OHI, fluoride and diet.
Saliva also acts as a buffer to plaque acids, also increasing this time.
What is rampant caries?
When the caries process is accelerated and lesions form rapidly.
What are the predisposing factors/4 groups of people does rampant caries affect most often?
Primary dentition with milk bottle caries.
Teens with a high sugar intake.
Drug addicts.
Adults with xerostomia- from Sjogren’s syndrome, or from therapeutic drugs that retard salivary flow.
What is Sjogren’s syndrome?
A chronic autoimmune condition characterized by degeneration of the salivary and lachrymal glands, causing dryness of the mouth and eyes.
What is arrested caries?
When a lesion has stopped progressing and it is inactive.
When does arrested caries occur?
When the oral environment conditions have changed from a carious one to conditions that slow caries progression.
What does arrested caries look like?
A dark, shiny, smooth exposed dentine surface.
What is the carious lesion?
The progressive destruction from the enamel surface to the pulp.
What are the conditions for the carious lesion’s ability to be arrested and reversed?
If it is only in enamel it can be arrested and reversed.
If it is in dentine, it can only be reversed if no proteolytic destruction of the organic collagen matrix has occurred.
How does dentine appear and feel when the caries is active?
Appears moist and matte.
Feels soft, wet and leathery on probing.
How does dentine appear and feel when caries is inactive?
Appears shiny and hard.
Scratchy on gentle probing.
What is the carious process within enamel?
Subsurface demineralisation from plaque acids causes POROSITES to form within the prism structure. This starts with the outer surface of enamel.
The presence of porosites in the subsurface layer is a result of the surface layer being mineralised by fluoride in toothpaste, and the remineralisation metabolism of the biofilm on the tooth surface.
The developing pore, volumes through the depth of the enamel lesion as a result of long exposure to reduced pH.
Why must the surface of enamel in the carious process remain intact and how can it heal?
The surface must remain intact, as it gives the lesion potential to heal.
It can heal if the biofilm is removed regularly and toothpastes containing high amounts of calcium and phosphates are used.