AGD Dental Materials & Technology 4

Question 1

What is the primary purpose of adding barium sulfate or strontium to composite resins?

Accepted Answer

Provide radiopacity for radiographic detection

Answer

Heavy metal salts like barium sulfate absorb X-rays, making composite restorations detectable on radiographs and distinguishable from recurrent caries.

Question 2

Which factor most significantly affects the working time of polyether impression materials compared to vinyl polysiloxane?

Accepted Answer

Polyether has a significantly shorter working time due to faster polymerization

Answer

Polyether materials typically offer 2–3 minutes of working time compared to the 4–5 minutes available with most VPS materials.

Question 3

Which type of stress does a cantilever pontic primarily place on the retaining abutment crown?

Accepted Answer

Torsional and bending (torque) stress

Answer

A cantilever pontic acts as a lever arm, generating rotational torque and bending moments that concentrate at the abutment connector.

Question 4

The Knoop hardness of enamel (~340 KHN) compared to dentin (~70 KHN) has which clinical implication for composite selection?

Accepted Answer

Restorations must withstand occlusal forces against a very hard substrate requiring adequate filler content

Answer

Because enamel is very hard, opposing restorations and the composite itself must have sufficient hardness and wear resistance to avoid premature wear.

Question 5

What is the function of the coupling agent (silane) applied to ceramic restoration surfaces before bonding?

Accepted Answer

Creates chemical bonds between the inorganic ceramic and organic resin cement

Answer

Silane is a bifunctional molecule with methoxysilyl groups that bond to silica in glass ceramics and methacrylate groups that co-polymerize with resin cement.

(AGD) Academy of General Dentistry Certification Practice Test

(AGD) Academy of General Dentistry Certification Practice Test

AGD Dental Materials & Technology 4