Oral histology and anatomy: dentine caries zones: 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.

Try it

Dentistry · Oral histology and anatomy: dentine caries zones

Sample item

A ground section of a carious tooth shows a zone of dentine ahead of the advancing bacteria that looks transparent because minerals have filled the tubules. What is this zone?

AZone of decomposed dentineBZone of demineralisationCZone of sclerosisDZone of bacterial invasion

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

The answer and the reasoning

C. Zone of sclerosis

The translucent zone, or zone of sclerosis, is the deepest layer of dentine caries, where calcium salts are deposited in the tubules as a defence. It lies ahead of the demineralised and infected zones.

Option by option

A. Zone of decomposed dentine
The decomposed zone is the superficial, grossly broken-down dentine.
B. Zone of demineralisation
The demineralisation zone is softened by acid and lies closer to the cavity than the sclerotic zone.
C. Zone of sclerosis (correct)
Correct. Tubules are occluded by mineral, making the dentine translucent.
D. Zone of bacterial invasion
The bacterial invasion zone contains microorganisms and is opaque, not transparent.

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 C, Zone of sclerosis. The translucent zone, or zone of sclerosis, is the deepest layer of dentine caries, where calcium salts are deposited in the tubules as a defence.

Why is "Zone of decomposed dentine" not the answer?

The decomposed zone is the superficial, grossly broken-down dentine.

Why is "Zone of demineralisation" not the answer?

The demineralisation zone is softened by acid and lies closer to the cavity than the sclerotic zone.

Why is "Zone of bacterial invasion" not the answer?

The bacterial invasion zone contains microorganisms and is opaque, not transparent.

What concept does this question test?

It tests Oral histology and anatomy: dentine caries zones in Dentistry. It lies ahead of the demineralised and infected zones.

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 Oral histology and anatomy: dentine caries zones?

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.