Restorative & Materials · patient case question
Below approximately what pH does enamel begin to demineralize?
Patient case: Soda habit with multiple deep lesions
Patient: 22-year-old patient who arrives sipping a soft drink.
Chief complaint: Sensitivity in several teeth.
History: Drinks two to three sodas daily, sipped over hours. Brushes once daily, no flossing, no fluoride rinse.
Findings: Multiple carious lesions across several quadrants, several radiographically extending into the inner third of dentin close to the pulp. All teeth respond normally to cold with no lingering pain and no periapical changes.
Show answer and explanation
Correct answer: B. 5.5
- A. 6.5 is above the enamel threshold, although it is within the demineralizing range for root dentin.
- B. CORRECT. The CRITICAL pH for enamel is approximately 5.5. Below that, plaque fluid is undersaturated with respect to hydroxyapatite and net mineral loss begins. Root surface dentin and cementum have a higher critical pH of about 6.2 to 6.7, which is why root caries progresses at pH values enamel would tolerate. Colas themselves sit near pH 2.5.
- C. pH 3 is far below critical and describes the drink itself rather than the threshold being asked for.
- D. 7.0 is neutral. Resting plaque pH sits above the critical value and enamel is stable.
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