Dental materials and radiology basics: eugenol and resin: 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 · Dental materials and radiology basics: eugenol and resin

Sample item

A dentist places zinc oxide eugenol as a sedative base in a deep cavity and then bonds a composite directly over it in the same visit. What is the likely problem?

AEugenol dissolves the glass filler particles of the compositeBComposite shrinks more over a zinc oxide eugenol baseCEugenol inhibits resin cure, so the composite sets poorlyDZinc oxide reacts with the etchant to give toxic fumes

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

The answer and the reasoning

C. Eugenol inhibits resin cure, so the composite sets poorly

Eugenol is a free-radical scavenger and interferes with the polymerisation of methacrylate resins, so the layer next to it stays soft and bonding is weak. Eugenol-containing bases should therefore be avoided under resin restorations, and a calcium hydroxide liner or glass ionomer is chosen instead.

Option by option

A. Eugenol dissolves the glass filler particles of the composite
Eugenol does not dissolve the inorganic filler; it acts on the resin matrix chemistry.
B. Composite shrinks more over a zinc oxide eugenol base
Shrinkage depends on the resin and technique, not on the type of base beneath it.
C. Eugenol inhibits resin cure, so the composite sets poorly (correct)
Correct. Eugenol quenches the free radicals needed for resin polymerisation.
D. Zinc oxide reacts with the etchant to give toxic fumes
Etchant does not generate toxic gas with zinc oxide; the issue is chemical inhibition of cure.

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, Eugenol inhibits resin cure, so the composite sets poorly. Eugenol is a free-radical scavenger and interferes with the polymerisation of methacrylate resins, so the layer next to it stays soft and bonding is weak.

Why is "Eugenol dissolves the glass filler particles of the composite" not the answer?

Eugenol does not dissolve the inorganic filler; it acts on the resin matrix chemistry.

Why is "Composite shrinks more over a zinc oxide eugenol base" not the answer?

Shrinkage depends on the resin and technique, not on the type of base beneath it.

Why is "Zinc oxide reacts with the etchant to give toxic fumes" not the answer?

Etchant does not generate toxic gas with zinc oxide; the issue is chemical inhibition of cure.

What concept does this question test?

It tests Dental materials and radiology basics: eugenol and resin in Dentistry. Eugenol-containing bases should therefore be avoided under resin restorations, and a calcium hydroxide liner or glass ionomer is chosen instead.

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: eugenol and resin?

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.