Caries, pulp and periodontal disease: subantimicrobial doxycycline: 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: subantimicrobial doxycycline

Sample item

Low-dose doxycycline (20 mg twice daily) is used as an adjunct in periodontitis. Which action explains its effect at this dose?

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

The answer and the reasoning

D. Inhibition of host matrix metalloproteinases such as collagenase

At subantimicrobial dose, doxycycline does not kill bacteria or change the flora but inhibits collagenase and other matrix metalloproteinases, reducing tissue destruction. It is used with scaling and root planing. Standard antibiotic doses act differently.

Option by option

  • A. Bactericidal killing of periodontal pathogens

    Bactericidal action needs a standard antibiotic dose.

  • B. Remineralisation of root surfaces

    Fluoride, not doxycycline, drives remineralisation.

  • C. Stimulation of salivary flow

    It has no sialogogue effect.

  • D. Inhibition of host matrix metalloproteinases such as collagenase (correct)

    Correct. It modulates the host response by blocking collagenase.

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.

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Questions about this Dentistry question

What is the answer to this Dentistry question?

The best answer is D, Inhibition of host matrix metalloproteinases such as collagenase. At subantimicrobial dose, doxycycline does not kill bacteria or change the flora but inhibits collagenase and other matrix metalloproteinases, reducing tissue destruction.

Why is "Bactericidal killing of periodontal pathogens" not the answer?

Bactericidal action needs a standard antibiotic dose.

Why is "Remineralisation of root surfaces" not the answer?

Fluoride, not doxycycline, drives remineralisation.

Why is "Stimulation of salivary flow" not the answer?

It has no sialogogue effect.

What concept does this question test?

It tests Caries, pulp and periodontal disease: subantimicrobial doxycycline in Dentistry. It is used with scaling and root planing. Standard antibiotic doses act differently.

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: subantimicrobial doxycycline?

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.