CAP 8- Dental caries - factors affecting imitation and progression of lesions

Question 1

what involved in the initation of the carious process?

Answer 1

Plaque formation (on a biofilm)

Question 2

what is a biofilm?

Answer 2

Community of micro-organisms attached to a surface

Question 3

Describe a biofilm.

Answer 3

-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

Question 4

Where can biofilms form?

Answer 4

• On enamel for coronal caries
• On root for root surface caries
• On the root canal when pulp has died off and become infected

Question 5

what is need for the imitation of the carious process?

Answer 5

susceptible tooth surface

Question 6

What happens to the susceptible tooth surface to innate the carious process?

Answer 6

-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)

Question 7

Describe the unique process of how occlusal caries starts and progresses.

Answer 7

-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)

Question 8

Name one common plaque stagnation area.

Answer 8

Approximal surface with adjacent tooth

Question 9

What happens at plaque stagnation areas?

Answer 9

• Gingival recession – root caries

- Adjacent to partial dentures

Question 10

What forms adjacent to restorations (around poorly polished and finished restorations)?

Answer 10

plaque stagnation areas

Question 11

Describe the microbial succession of the carious process.

Answer 11

Strept in first 1-4 deominate

But over 1-14 days this dominance can change to actinomyces

Question 12

what is acidogenic?

Answer 12

transport sugars in diet and convert to acid – lactic acid

Question 13

What is converted to acid?

Answer 13

Extracellular and intracellular polysaccarides – plaque matrix

Question 14

What is aciduric?

Answer 14

thrive at low pH

Question 15

what is the specific plaque hypothesis?

Answer 15

• Approx 300 species of intra-oral micro-organisms
• Specific limited number involved in carious process
• ? immunise against these

Question 16

What is the non-specific plaque hypothesis?

Answer 16

• Caries results from the over-all activity of the micro-organisms within the biofilm
• All plaque should be removed

Question 17

What is the ecological plaque hypothesis?

Answer 17

-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

Question 18

Describe the Stephan curve.

Answer 18

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)

Question 19

what autoimmune conditions produce a lot of caries?

Answer 19

Autoimmune conditions such as sjorgens that have a lack of saliva

Question 20

Describe what is seen in a ground section examined in polarised light -imbibition in water.

Answer 20

• 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

Question 21

What 2 zones are seen in ground sections examined in polarised light - ambition in quinoline?

Answer 21

• Translucent zone

- dark zone

Question 22

Name the 2 zones of carious dentine.

Answer 22

• the outer zone

- the inner zone

Question 23

Describe the outer zone.

Answer 23

-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

Question 24

Describe the inner zone.

Answer 24

-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).

Question 25

what challenges the biofilm?

Answer 25

- Fissure sealant studies - Ultraconservative caries removal - Stepwise excavation - Hall technique

Question 26

what are fissure sealants?

Answer 26

- 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

Question 27

what effect does acid etch have alone?

Answer 27

75% reduction in viable organisms

Question 28

What happens in the first visit of stepwise excavation?

Answer 28

- 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

Question 29

What happens in the second visit of stepwise excavation?

Answer 29

Re-clean cavity and restore

Question 30

Describe the outcome of a clinical and microbiological study of deep carious lesions during stepwise excavation using long treatment intervals.

Answer 30

- 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

Question 31

What is ultraconservative caries removal?

Answer 31

Clinical performance of sealed composite restorations placed over caries compared with sealed and unsealed amalgam restorations

Question 32

Describe how ultraconservative caries removal works.

Answer 32

- 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

Question 33

How does microbiology affect caries?

Answer 33

- 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