Aetiology of Caries Flashcards
What are dental caries?
bacterial disease of calcified tissues of the teeth characterised by the demineralisation of the inorganic and destruction of the organic substance of the tooth
What’s the Acidogenic theory?
- Caries is the result from a shift in metabolic activity accompanied by a gradual change in ecology of the dental biofilm
- Acid production by oral bacteria as a result of carbohydrate fermentation leads to decalcification of the hard tissue tooth substance and disintegration of the organic matrix
What are Primary modifying factors for Dental Caries?
- Tooth Anatomy
- Saliva
- Biofilm pH
- Use of Fluoride
- Oral hygiene
- Immune System
What are the Secondary modifying factors for Dental Caries?
- Socioeconomic status
- Education
- Life-style
- Environment
- Occupation
What’s the development of dental biofilms?
- Pellicle formation
- Attachment of eary bacterial colonisers (0-14hrs)
- Co-adhesion and growth of attached bacteria leading to the formation of microcoloconies (4-24hrs)
4 Microbial succession leading to increased species diversity concomitant with continued co-adhesion and growth of microcolonies (1-7 days) - Climax community/mature biofilm (1 week +)
What are examples of the Initial colonisers?
Streptococci: Sangius, Oralis, Mitis
- 95% of the Streptococci
- Actinomyces spp
Nutrients: from endogenous molecules from saliva
What are the next colonisers of biofilm?
- Actinomyces dominate
- Bacteria produce polysaccharodes and these contribute to the biofilm matrix
What’s the composition of a mature biofilm?
- Diverse composition
- Majority are facultative or obligately anaerobic
- Acid producing gram+ cocci
What are the cariogenic features of dental biofilm bacteria?
- Rapidly transport fermentable sugars when in competition with other plaque bacteria - conversion of such sugars to ACID
- Maintain sugar metabolism under extreme environmental conditions (low pH)
- Production of extracellular and intracellular polysaccharides
Microbiology of Dental Caries: Does Streptococci Mutans play a role?
- It plays an important role in caries initiation, while other bacteria such as lactobacilli may be important in lesion progression
Are Lactobacilli important in dentine caries?
YES
- Contributes to demineralisation of teeth once lesions are established
What’s special about Oral Actinomyces?
- Gram + , non-spore, rods and filaments
- Goof plaque former
- ALL SPECIES FERMENT GLUCOSE AND MOSTLY PRODUCE LACTIC ACID
- A. Ciccosus + naeslundii have the ability to INDUCE ROOT CARIES
What are some of the Intrinsic factors for caries susceptibility?
- Enamel composition
- Enamel structure
- Tooth morphology
- Tooth position
What are some of the extrinsic factors for caries susceptibility?
- Saliva
- Diet
- Use of fluoride
- Immunity
What’s the resting plaque pH?
- 6.5-7
What happens to the pH in the mouth after an oral rinse of sucrose?
- Drops to 5 within 2-3 minutes
- Takes 20 minutes for the pH to go back to normal
The speed with which pH drops is an indicator of?
- The speed of sugar metabolism in the plaque
What happens to dietary sugars when they interact with plaque?
- They diffuse through the plaque
- Convert into lactic acid (mainly), acetic and propionic acids by bacteria
What’s the critical pH?
5.5 - below this enamel begins to dissolve
Can bacteria store Carbohydrates?
- YES
- They can store them and use them at a later date
What’s the role of Polysaccharides in plaque formation and cariogenesis?
- Plaque store glucose as glycogen
- S.mutans synthesise other polymers given access to sucrose
- Increases the bulk of the plaque and are more cariogenic
- Glucans & Fructans are deposited extracellularly thus providing a voluminous sticky environment for the plaque organisms
The ability of microorganisms to form plaque on teeth is directly related to…
- Their ability to synthesis glucans and fructans
- Plaque control methods have targeted Glucosyltransferases
Is plaque composition influenced by diet?
- YES
- S.mutans are more prevalent with sucrose rich diets
- Lactobacilli is acid tolerant and gound in greater proportions in carious cavities
Why is sucrose important in caries development?
- Sucrose intake affects the composition of early plaque leading to higher numbers of bacterial species capable of synthesising glucan from sucrose
How does Sucrose alter the composition of plaque?
- Makes it bulkier due to increased Glucan and Fructan secretions
Are non-sugar sweeteners cariogenic?
- NO
- Some have caries preventative features (xylitol)
How might sugarfree chewing gum prevent caries?
- Increases salivary flow rate and doesn’t contain sugar to feed the plaque
What are the preventative qualities of Xylitol?
- Affects bacterial growth and metabolism
- Reduced biofilm formation
- Decreases the number of S.mutans
What effect do Fluoride ion have on plaque?
- Inhibit bacterial metabolism
What happens to Hydroxyapatite crystals with Carbonate incorporation?
- Promotes the carious attack
