Caries, pulp and periodontal disease: Stephan curve: practice question

A Dentistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Dentistry · Caries, pulp and periodontal disease: Stephan curve

Sample item

A student plots plaque pH after a sucrose rinse and observes a rapid drop followed by slow recovery. Which statement about the curve is correct?

AThe curve is flat if saliva flow is highBpH falls within minutes and takes about 30 to 60 minutes to return toward baselineCpH rises first and then falls after 2 hoursDpH remains unchanged in plaque

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. pH falls within minutes and takes about 30 to 60 minutes to return toward baseline

The Stephan curve records a fall in plaque pH to around 5 within 5 to 10 minutes of a sugar challenge, with recovery over 30 to 60 minutes. Frequent exposure keeps the pH low for longer.

Option by option

A. The curve is flat if saliva flow is high
High salivary flow speeds recovery but does not abolish the fall.
B. pH falls within minutes and takes about 30 to 60 minutes to return toward baseline (correct)
Correct. A sharp fall and slow recovery describes the curve.
C. pH rises first and then falls after 2 hours
The pH falls immediately after sugar and does not rise first.
D. pH remains unchanged in plaque
Plaque pH does fall after sugar, which is the whole principle of the curve.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Dentistry question

What is the answer to this Dentistry question?

The best answer is B, pH falls within minutes and takes about 30 to 60 minutes to return toward baseline. The Stephan curve records a fall in plaque pH to around 5 within 5 to 10 minutes of a sugar challenge, with recovery over 30 to 60 minutes.

Why is "The curve is flat if saliva flow is high" not the answer?

High salivary flow speeds recovery but does not abolish the fall.

Why is "pH rises first and then falls after 2 hours" not the answer?

The pH falls immediately after sugar and does not rise first.

Why is "pH remains unchanged in plaque" not the answer?

Plaque pH does fall after sugar, which is the whole principle of the curve.

What concept does this question test?

It tests Caries, pulp and periodontal disease: Stephan curve in Dentistry. Frequent exposure keeps the pH low for longer.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Caries, pulp and periodontal disease: Stephan curve?

Learn the dental formula, eruption ages and tooth structure once, as tables. Then use the flashcards and the other Dentistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.