Demineralization of enamel occurs at what pH range?

• A. 3.0-3.5
• B. 4.5-5.5
• C. 6.5-7.5
• D. 7.5-8.5

Answer: (B)

Enamel demineralization begins when the acid produced by plaque bacteria lowers the local pH enough for hydroxyapatite to dissolve. The critical pH for enamel is about 5.5, so mineral loss starts once the pH falls into the mid-acidic range. The range 4.5 to 5.5 captures this window where demineralization occurs most readily, since acids within this span push the enamel toward mineral loss. Saliva can buffer and provide minerals to promote remineralization when pH rises again, and fluoride helps strengthen enamel against acid attack. Values at neutral or higher pH don’t drive demineralization, while extremely low pH would cause rapid loss but is less representative of typical oral conditions.