Microbiology of Caries

Question 1

What are the four key factors involved in caries progression?

what is the cycle they interact in?

Answer 1

Saliva, Diet, Microbiota, and Tooth.

These factors interact in a cycle of: Adhesion → Survival & growth → Biofilm formation → Complex plaque → Acid → Caries

Question 2

What are the key characteristics that make Streptococcus mutans considered an “arch villain” in caries?

Answer 2

• Glycolytic systems
• EPS/sucrose metabolism
• Attachment mechanisms (GTF, Ag I/II)
• Greater acidogenicity/aciduricity compared to competitor species
• Ecological competitiveness at low pH
• Specific genomic characteristics
• Clear link between S. mutans presence and caries
• Mutans strep proportions linked to high sugar diet

Question 3

Why is the relationship between S. mutans and caries being questioned?

Answer 3

The clinical evidence for frequent sugar consumption in caries etiology is much stronger than the belief that caries is an infectious disease caused by mutans streptococci.

Question 4

What makes carbohydrates besides sucrose cariogenic?

Answer 4

Cooked starches (like crisps and biscuits) can be cariogenic
“Sticky in the hand = sticky in the mouth” principle
Food retentivity is crucial
Micro-analytical methods provide supporting evidence
Some starches can yield prolonged glucose challenge leading to lactic acid production

Question 5

What were the key findings from Arcella et al (2002) and Campain et al (2003) regarding starch and caries?

Answer 5

Arcella et al findings:

• Starch can be equal to sugar in importance
• Starches can be as harmful or worse than chocolate
• Frequency of dietary intake is critical

Campain et al findings:

• Demonstrated interactions between sugar and starch concentrations
• Only low sugar/high starch combination was associated with caries

Question 6

How has molecular biology expanded our understanding of caries etiology?

Answer 6

• Revealed hundreds or thousands of microbial species in oral microbiome
• Identified wide spectrum of flora associated with caries
• Found subjects with caries but no S. mutans
• Showed mutans-streps presence is not predictive of caries

Question 7

What are the key findings regarding diet and microbial etiology in Severe Early Childhood Caries (SECC)?

Answer 7

• Presence of Bifidobacterium spp, lactobacilli, yeast (and mutans streps)
• Conditions favor mutans streps rather than mutans streps being a prerequisite
• Supports new paradigm of more complex oral microbial world
• Confirms “the environment selects” principle (Alexander, 1970)
• Supports ecological plaque hypothesis (Marsh, 1991)

Question 7

What were the findings of the study on occlusal surface biofilms in 12-year-olds?

Answer 7

• Study analyzed rRNA amplicon from occlusal surfaces
• Sites were classified as sound or adult white spot lesions (AWSL)
• S. mutans was found on all surfaces
• 18 distinct taxa were associated with disease
• Neither S. mutans nor lactobacilli were associated with AWSL sites
• S. sobrinus was only found in 3 out of 13 subjects