Oral histology and anatomy: width of periodontal ligament: 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: width of periodontal ligament

Sample item

Along the root of a healthy tooth, in which region is the periodontal ligament space narrowest, close to the axis of rotation?

ACervical third of the rootBFurcation areaCMiddle third of the rootDApical third of the root

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

The answer and the reasoning

C. Middle third of the root

The periodontal ligament space is narrowest in the middle third of the root, near the fulcrum around which the tooth rotates, and widest near the alveolar crest and apex. Its average width is about 0.2 mm and it decreases with age.

Option by option

A. Cervical third of the root
The cervical third is wider because of its closeness to the crest.
B. Furcation area
The furcation area is wide and contains interradicular fibres.
C. Middle third of the root (correct)
Correct. The space is thinnest in the middle third, near the axis of rotation.
D. Apical third of the root
The apical third is wider and carries the apical vessels and nerves.

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, Middle third of the root. The periodontal ligament space is narrowest in the middle third of the root, near the fulcrum around which the tooth rotates, and widest near the alveolar crest and apex.

Why is "Cervical third of the root" not the answer?

The cervical third is wider because of its closeness to the crest.

Why is "Furcation area" not the answer?

The furcation area is wide and contains interradicular fibres.

Why is "Apical third of the root" not the answer?

The apical third is wider and carries the apical vessels and nerves.

What concept does this question test?

It tests Oral histology and anatomy: width of periodontal ligament in Dentistry. Its average width is about 0.2 mm and it decreases with age.

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: width of periodontal ligament?

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.