Dental materials and radiology basics: zirconia transformation toughening: 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 · Dental materials and radiology basics: zirconia transformation toughening

Sample item

Yttria-stabilised zirconia crowns resist crack propagation better than most dental ceramics. Which mechanism is responsible?

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

The answer and the reasoning

D. Stress-induced tetragonal to monoclinic change

In partially stabilised zirconia the tetragonal phase transforms to the monoclinic phase under the stress at a crack tip. This change is accompanied by a volume increase that squeezes the crack closed. This transformation toughening gives zirconia its high flexural strength.

Option by option

  • A. Ductile plastic flow of the ceramic at the crack tip

    Ceramics do not flow plastically at body temperature; they fracture in a brittle way.

  • B. A glassy matrix that blunts cracks by softening

    Zirconia is polycrystalline with little glass, and glass phases do not toughen it.

  • C. Chemical bonding of the ceramic surface to silane

    Silane improves bonding to glass ceramics and has no role in zirconia crack resistance.

  • D. Stress-induced tetragonal to monoclinic change (correct)

    Correct. The stress-induced phase change expands locally and closes the advancing crack.

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.

More Dentistry questions

Questions about this Dentistry question

What is the answer to this Dentistry question?

The best answer is D, Stress-induced tetragonal to monoclinic change. In partially stabilised zirconia the tetragonal phase transforms to the monoclinic phase under the stress at a crack tip.

Why is "Ductile plastic flow of the ceramic at the crack tip" not the answer?

Ceramics do not flow plastically at body temperature; they fracture in a brittle way.

Why is "A glassy matrix that blunts cracks by softening" not the answer?

Zirconia is polycrystalline with little glass, and glass phases do not toughen it.

Why is "Chemical bonding of the ceramic surface to silane" not the answer?

Silane improves bonding to glass ceramics and has no role in zirconia crack resistance.

What concept does this question test?

It tests Dental materials and radiology basics: zirconia transformation toughening in Dentistry. This change is accompanied by a volume increase that squeezes the crack closed. This transformation toughening gives zirconia its high flexural strength.

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: zirconia transformation toughening?

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.