AGD Dental Materials and Application 3

Question 1

Which mechanism is responsible for the self-adhesive property of glass ionomer cement to tooth structure?

Accepted Answer

Chelation of polyacrylic acid with calcium in hydroxyapatite

Answer

GIC bonds chemically via chelation between the carboxylate groups of polyacrylic acid and calcium ions in hydroxyapatite, requiring no separate etching step.

Question 2

What is the working time of a dental material most directly influenced by?

Accepted Answer

The operator's mixing technique and temperature

Answer

Working time is primarily affected by mixing technique (spatulation rate/area) and ambient temperature — higher temperatures accelerate the reaction and shorten working time.

Question 3

A flowable composite would be preferred over a packable composite in which clinical situation?

Accepted Answer

Lining the internal walls of a deep Class I preparation

Answer

Flowable composites are ideal as liners in cavity preparations due to their low viscosity, easy adaptation, and elastic modulus that provides a stress-absorbing layer.

Question 4

Galvanic corrosion in the mouth is most likely to occur when:

Accepted Answer

Dissimilar metals contact each other in the presence of saliva

Answer

Galvanic corrosion results from electrochemical reactions between dissimilar metals connected through an electrolyte such as saliva, generating a small electric current.

Question 5

Which cement is contraindicated as a final luting agent for porcelain-fused-to-metal crowns due to its high acidity?

Accepted Answer

Zinc phosphate cement

Answer

Zinc phosphate cement's initial low pH (~2) can cause transient pulpal inflammation and is generally considered less biocompatible than newer cements for final cementation.

(AGD) Academy of General Dentistry Certification Practice Test

(AGD) Academy of General Dentistry Certification Practice Test

AGD Dental Materials and Application 3