CAP 8- Dental caries - factors affecting imitation and progression of lesions Flashcards
what involved in the initation of the carious process?
Plaque formation (on a biofilm)
what is a biofilm?
Community of micro-organisms attached to a surface
Describe a biofilm.
-Community with collective physiology – work together and interact
-Commensal organisms
-Site to site variability
Tooth surface
Within the Biofilm
-Extra-cellular material
>Bacterial
>Oral Cavity
Where can biofilms form?
- On enamel for coronal caries
- On root for root surface caries
- On the root canal when pulp has died off and become infected
what is need for the imitation of the carious process?
susceptible tooth surface
What happens to the susceptible tooth surface to innate the carious process?
-Pellicle formation:
Acellular, proteinaceous film derived from saliva
-Bacterial colonization (0-4 hours) in stagnation areas (S. sanguis, S. oralis, S. mitis, Actinomyses species, Gram negative bacteria, mutans streptocci (2%))
-Microcolony formation (4-24 hours)
Describe the unique process of how occlusal caries starts and progresses.
-Biofilm will start to form bacteria in the biofilm will break down any sugar to produce acid and cause demineralisation
-Contines to get deeper until it hits ADJ and then the areas of demineralisation will merger causing a larger area
(Fluroide makes the enamel strongers and more resistant to this process)
Name one common plaque stagnation area.
Approximal surface with adjacent tooth
What happens at plaque stagnation areas?
- Gingival recession – root caries
- Adjacent to partial dentures
What forms adjacent to restorations (around poorly polished and finished restorations)?
plaque stagnation areas
Describe the microbial succession of the carious process.
Strept in first 1-4 deominate
But over 1-14 days this dominance can change to actinomyces
what is acidogenic?
transport sugars in diet and convert to acid – lactic acid
What is converted to acid?
Extracellular and intracellular polysaccarides – plaque matrix
What is aciduric?
thrive at low pH
what is the specific plaque hypothesis?
- Approx 300 species of intra-oral micro-organisms
- Specific limited number involved in carious process
- ? immunise against these
What is the non-specific plaque hypothesis?
- Caries results from the over-all activity of the micro-organisms within the biofilm
- All plaque should be removed
What is the ecological plaque hypothesis?
-Plaque can accumulate at all tooth sites
-Balance of microflora can change depending on local environment:
>Sugar
>Saliva
>Stagnation areas
-Favours aciduric and acidogenic species
-Remove plaque from susceptible sites and decrease frequency of sugar intake
Describe the Stephan curve.
pH within the biofilm on the surface pf the tooth will decrease after sucrose rinse and then buffering of saliva will increase and the pH will rise
(cariogenicty under 5.5)
what autoimmune conditions produce a lot of caries?
Autoimmune conditions such as sjorgens that have a lack of saliva
Describe what is seen in a ground section examined in polarised light -imbibition in water.
- When section is soaked in water you will see 2 zones
- Majority of mineral is lost in body of lesion
- Surface zone has very low demineralisation
- Thickenes of surface zone can indicate speed of caries – slow caries has a thicker surface zone
What 2 zones are seen in ground sections examined in polarised light - ambition in quinoline?
- Translucent zone
- dark zone
Name the 2 zones of carious dentine.
- the outer zone
- the inner zone
Describe the outer zone.
-The outer zone - demineralised, collagen denatured, infected and not remineralisable:
>Note for occlusal caries, only lesions radiographically visible extend to middle third of dentine and beyond, and are heavily infected.
>For proximal lesions lesions deeper clinically than they appear radiographically
Describe the inner zone.
-The inner zone - Dentine is demineralised, minimally infected, collagen fibers intact and dentine remineralisable.
>Note in deep caries, bacteria within the lesion obtain substrate from oral cavity, and possibly pulp (tissue glucose).
what challenges the biofilm?
- Fissure sealant studies
- Ultraconservative caries removal
- Stepwise excavation
- Hall technique
what are fissure sealants?
- Low viscosity resins that flow inton the poits and fissures of posterior teeth
- Primary prevention and also used above caries lesions that extend into the dentine
what effect does acid etch have alone?
75% reduction in viable organisms
What happens in the first visit of stepwise excavation?
- Remove only superficial layer of infected necrotic dentine.
- Ensure peripheral caries removal complete.
- Place Ca OH lining and Glass Ionomer.
- Leave for 6-12 months for pulp dentine complex reactions
What happens in the second visit of stepwise excavation?
Re-clean cavity and restore
Describe the outcome of a clinical and microbiological study of deep carious lesions during stepwise excavation using long treatment intervals.
- All sites after first excavation were soft, wet, pale and heavily infected
- sealed for 6-12 months
- all became harder, dry , dark and reduction in level of infection
What is ultraconservative caries removal?
Clinical performance of sealed composite restorations placed over caries compared with sealed and unsealed amalgam restorations
Describe how ultraconservative caries removal works.
- Remove superficial bit of tissue and apply composite
- Composite is thoigh to be stronger than a fissure seal
- No change in lesuons after 10 years no further deterioration
How does microbiology affect caries?
- Decrease in microbial load
- Reduction in microbial diversity
- Reduction in nutrient amount and complexity – derived from pulp
- Pulpal nutrient decrease in time with pulp dentine complex reactions
