alleryStart learning →Tooth decay begins when the pH of the mouth falls below about
A7.0
B5.5
C8.5
D10.0
Answer & Solution
Correct answer: B. 5.5
1. Bacteria in the mouth produce acids from sugar.
2. When the pH of the mouth drops **below 5.5**, tooth enamel (calcium phosphate) starts to corrode.
3. Using a basic toothpaste neutralises the excess acid and prevents decay.
_Source: Karnataka SSLC (KSEEB) Class 10 Science, Ch2 'Acids, Bases and Salts', §2.3 (pH in everyday life)_
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