Orthodontics and paediatric dentistry: Tanaka-Johnston mixed dentition analysis: 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: Tanaka-Johnston mixed dentition analysis

Sample item

In the Tanaka-Johnston mixed dentition analysis, the space needed for the unerupted mandibular canine and premolars on one side is estimated from which measurement?

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

The answer and the reasoning

A. Half the mesiodistal width of the four mandibular incisors plus a constant

Tanaka-Johnston predicts the combined width of the unerupted canine and premolars as one half of the sum of the four mandibular incisors plus 10.5 mm for the mandibular arch and 11 mm for the maxillary arch. The prediction is compared with the available space. Moyers uses probability tables from the same incisor measurement.

Option by option

  • A. Half the mesiodistal width of the four mandibular incisors plus a constant (correct)

    Correct. Half the mandibular incisor width plus a constant gives the estimate.

  • B. The width of the first permanent molars

    Molar widths are not used in this prediction.

  • C. The arch length multiplied by two

    Arch length is a measure of available, not needed, space.

  • D. The width of the maxillary central incisors alone

    Maxillary central incisors alone are not the basis for the lower arch estimate.

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 A, Half the mesiodistal width of the four mandibular incisors plus a constant. Tanaka-Johnston predicts the combined width of the unerupted canine and premolars as one half of the sum of the four mandibular incisors plus 10.

Why is "The width of the first permanent molars" not the answer?

Molar widths are not used in this prediction.

Why is "The arch length multiplied by two" not the answer?

Arch length is a measure of available, not needed, space.

Why is "The width of the maxillary central incisors alone" not the answer?

Maxillary central incisors alone are not the basis for the lower arch estimate.

What concept does this question test?

It tests Orthodontics and paediatric dentistry: Tanaka-Johnston mixed dentition analysis in Dentistry. 5 mm for the mandibular arch and 11 mm for the maxillary arch. The prediction is compared with the available space. Moyers uses probability tables from the same incisor measurement.

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 Orthodontics and paediatric dentistry: Tanaka-Johnston mixed dentition analysis?

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.