Dental materials and radiology basics: radiographic proximal caries: 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 · Dental materials and radiology basics: radiographic proximal caries

Sample item

On a bitewing radiograph, a proximal carious lesion reaches the dentine. Where does the base of the radiolucent triangle lie in the dentine?

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

The answer and the reasoning

D. At the dentinoenamel junction

Caries spreads laterally at the dentinoenamel junction and then along the dentinal tubules towards the pulp. In enamel, the triangle has its base at the surface and its apex at the junction, while in dentine the base lies at the junction and the apex points to the pulp. This helps in recognising dentine involvement.

Option by option

  • A. At the cementoenamel junction

    The cementoenamel junction is a cervical landmark and not where dentine caries spreads laterally.

  • B. Against the pulp chamber

    The apex, not the base, points to the pulp because tubules converge.

  • C. At the proximal tooth surface

    The base of the enamel triangle is at the surface, not that of the dentine lesion.

  • D. At the dentinoenamel junction (correct)

    Correct. The dentinal triangle has its base at the dentinoenamel junction and apex towards the pulp.

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, At the dentinoenamel junction. Caries spreads laterally at the dentinoenamel junction and then along the dentinal tubules towards the pulp.

Why is "At the cementoenamel junction" not the answer?

The cementoenamel junction is a cervical landmark and not where dentine caries spreads laterally.

Why is "Against the pulp chamber" not the answer?

The apex, not the base, points to the pulp because tubules converge.

Why is "At the proximal tooth surface" not the answer?

The base of the enamel triangle is at the surface, not that of the dentine lesion.

What concept does this question test?

It tests Dental materials and radiology basics: radiographic proximal caries in Dentistry. In enamel, the triangle has its base at the surface and its apex at the junction, while in dentine the base lies at the junction and the apex points to the pulp. This helps in recognising dentine involvement.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Dental materials and radiology basics: radiographic proximal caries?

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.