A patient arrives having just finished an energy drink. What is the most likely pH in the mouth at that moment?

Correct answer: A. Around 5.0 or lower

• A. CORRECT. Energy drinks and sports drinks are strongly acidic, most measuring between pH 2.5 and 3.5 in the can, driven by citric, phosphoric and malic acid. Immediately after consumption the oral pH plunges well below the CRITICAL pH of 5.5 for enamel, and salivary buffering takes 20–40 minutes to bring it back. Of the values offered, 5.0 or lower is the answer.
• B. 7.5 is slightly alkaline and does not occur after an acidic drink.
• C. 8.0 is well above any physiological oral pH following acid exposure.
• D. 6.5 is close to resting salivary pH and would represent a mouth that has already recovered.

Note: Critical pH values worth memorising: enamel demineralises below 5.5, root/dentine below about 6.2 — which is why root surfaces are so much more vulnerable. Advise rinsing with water, waiting 30–60 minutes before brushing, and using a straw.