Which hypothesis describes that non-mutans bacteria in the right biofilm environment can adapt to produce acid and destabilize plaque, leading to demineralization?

• A. Extended caries ecological hypothesis
• B. Specific plaque hypothesis
• C. Non-cariogenic bacteria theory
• D. Genetic virulence model

Answer: (A)

The concept being tested is that dental caries arise from ecological shifts in the plaque biofilm in response to the oral environment, allowing a broader range of bacteria to become acid producers and drive demineralization. The extended caries ecological hypothesis says it’s not just one species (like mutans streptococci) that matters; when conditions such as frequent sugar intake lower the biofilm pH, many non-mutans bacteria can adapt to become acidogenic. This shift in the microbial community leads to more acid in the plaque, keeping the pH below the critical level for enamel and dentin and promoting demineralization.

In other words, caries result from the environment selecting for acid-producing bacteria within the biofilm, and not from a single pathogen alone. The other choices describe more singular ideas (a single pathogen driving caries, or entirely non-cariogenic bacteria, or a host-genetics focus) that don’t capture the community-wide, environmental shift described here.