Orthodontics and paediatric dentistry: Tweed triangle: 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 · Orthodontics and paediatric dentistry: Tweed triangle

Sample item

The Tweed diagnostic triangle is used in cephalometric planning. Which three angles make up the triangle?

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

The answer and the reasoning

B. FMA, IMPA and FMIA

The Tweed triangle consists of the Frankfort mandibular plane angle (FMA), the incisor mandibular plane angle (IMPA) and the Frankfort mandibular incisor angle (FMIA). A favourable FMIA of about 65 degrees was the treatment goal. It was used to decide extraction and anchorage needs.

Option by option

  • A. SNA, SNB and ANB

    SNA, SNB and ANB are Steiner skeletal angles.

  • B. FMA, IMPA and FMIA (correct)

    Correct. FMA, IMPA and FMIA are the angles of the Tweed triangle.

  • C. Interincisal angle, SN-MP and Y axis

    These are other cephalometric measures and are not the triangle.

  • D. Facial angle, angle of convexity and A-B plane

    These angles belong to the Downs analysis.

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 B, FMA, IMPA and FMIA. The Tweed triangle consists of the Frankfort mandibular plane angle (FMA), the incisor mandibular plane angle (IMPA) and the Frankfort mandibular incisor angle (FMIA).

Why is "SNA, SNB and ANB" not the answer?

SNA, SNB and ANB are Steiner skeletal angles.

Why is "Interincisal angle, SN-MP and Y axis" not the answer?

These are other cephalometric measures and are not the triangle.

Why is "Facial angle, angle of convexity and A-B plane" not the answer?

These angles belong to the Downs analysis.

What concept does this question test?

It tests Orthodontics and paediatric dentistry: Tweed triangle in Dentistry. A favourable FMIA of about 65 degrees was the treatment goal. It was used to decide extraction and anchorage needs.

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 Orthodontics and paediatric dentistry: Tweed triangle?

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.