Community dentistry: chlorhexidine and toothpaste detergent: 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 · Community dentistry: chlorhexidine and toothpaste detergent

Sample item

A patient rinses with chlorhexidine immediately after brushing and the antiplaque effect is much reduced. What is the most likely reason?

AAnionic toothpaste detergent inactivates chlorhexidineBToothpaste abrasives strip chlorhexidine from the enamelCSaliva buffers inactivate chlorhexidine within secondsDChlorhexidine works only in a strongly alkaline medium

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

The answer and the reasoning

A. Anionic toothpaste detergent inactivates chlorhexidine

Chlorhexidine is a cationic antiseptic, and the anionic sodium lauryl sulphate and some other ingredients in toothpastes bind and inactivate it. The patient should rinse with water and wait, or use the mouthwash at a different time. This interaction is why it is not mixed with ordinary toothpaste.

Option by option

A. Anionic toothpaste detergent inactivates chlorhexidine (correct)
Correct. Anionic detergent binds the cationic chlorhexidine and inactivates it.
B. Toothpaste abrasives strip chlorhexidine from the enamel
Abrasives act on plaque and stain, and do not specifically remove chlorhexidine from enamel.
C. Saliva buffers inactivate chlorhexidine within seconds
Saliva does not inactivate chlorhexidine within seconds; its substantivity lasts hours.
D. Chlorhexidine works only in a strongly alkaline medium
Chlorhexidine is effective at the ordinary oral pH and does not need an alkaline medium.

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 A, Anionic toothpaste detergent inactivates chlorhexidine. Chlorhexidine is a cationic antiseptic, and the anionic sodium lauryl sulphate and some other ingredients in toothpastes bind and inactivate it.

Why is "Toothpaste abrasives strip chlorhexidine from the enamel" not the answer?

Abrasives act on plaque and stain, and do not specifically remove chlorhexidine from enamel.

Why is "Saliva buffers inactivate chlorhexidine within seconds" not the answer?

Saliva does not inactivate chlorhexidine within seconds; its substantivity lasts hours.

Why is "Chlorhexidine works only in a strongly alkaline medium" not the answer?

Chlorhexidine is effective at the ordinary oral pH and does not need an alkaline medium.

What concept does this question test?

It tests Community dentistry: chlorhexidine and toothpaste detergent in Dentistry. The patient should rinse with water and wait, or use the mouthwash at a different time. This interaction is why it is not mixed with ordinary toothpaste.

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 Community dentistry: chlorhexidine and toothpaste detergent?

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.