Free AGD Dental Materials and Application Questions and Answers

Question 1

A dentist is taking a final impression for a three-unit fixed partial denture. The preparation margins are equigingival, and excellent moisture control is challenging. The dentist requires a material with high tear strength, outstanding dimensional stability, and inherent hydrophilicity to capture fine detail in a moist environment. Which impression material would be the most suitable choice?

Accepted Answer

Polyether

Answer

Polyether is an ideal choice for this scenario because it is inherently hydrophilic, meaning it performs well in moist environments and can capture fine details even with slight moisture presence. It also possesses high tear strength and excellent dimensional stability, which are critical for an accurate multi-unit fixed prosthesis master cast. While PVS has good properties, it is naturally hydrophobic and relies on added surfactants to work in moist areas. Alginate lacks the dimensional stability and tear strength required for fixed prosthodontics.

Question 2

To achieve a durable and retentive bond to a monolithic zirconia crown, which of the following surface treatment and priming combinations is considered the gold standard?

Accepted Answer

Airborne-particle abrasion with aluminum oxide followed by the application of a 10-MDP-containing primer.

Answer

Zirconia is a high-strength, non-glass polycrystalline ceramic, which means it cannot be effectively etched with hydrofluoric acid. The most effective and evidence-based protocol for bonding to zirconia involves creating micromechanical retention via airborne-particle abrasion (sandblasting) and then establishing a chemical bond using a primer that contains the 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) monomer. The phosphate ester group of 10-MDP forms a strong, water-resistant chemical bond with the zirconium oxide surface.

Question 3

Which of the following components in a modern hybrid composite resin is primarily responsible for providing radiopacity, allowing the restoration to be distinguished from tooth structure and secondary caries on a radiograph?

Accepted Answer

Barium, Strontium, or Zirconium glass fillers

Answer

The resin matrix, silane, and photoinitiators are organic components with low atomic numbers, making them radiolucent. To make composite restorations visible on radiographs, manufacturers incorporate filler particles containing elements with high atomic numbers, such as barium, strontium, or zirconium, into the glass filler. These heavy metal ions are radiopaque, allowing the final restoration to have a radiodensity similar to or greater than enamel, which aids in diagnosing recurrent caries at the margin.

Question 4

A dental assistant needs to pour diagnostic casts that will be used for patient education and the fabrication of custom whitening trays. The primary requirements are adequate surface detail, sufficient strength for handling, and cost-effectiveness. Which ADA type of gypsum product is most appropriate for this task?

Accepted Answer

Type III Dental Stone

Answer

According to ADA Specification No. 25, Type III Dental Stone is the standard material for fabricating diagnostic casts (study models) and working models for removable prosthodontics. It provides a good balance of strength, accuracy, and cost for these applications. Type II Plaster is generally too weak, while Type IV and V die stones are unnecessarily strong, dense, and expensive for this purpose.

Question 5

What is the primary clinical advantage of using a Resin-Modified Glass Ionomer (RMGI) cement for luting a metal-based crown compared to a conventional glass ionomer cement?

Accepted Answer

Improved early mechanical properties and lower initial solubility.

Answer

The addition of a resin component (like HEMA) to conventional glass ionomer improves its physical properties. RMGI cements have higher initial fracture toughness and flexural strength, and are much less soluble in oral fluids during the critical initial setting phase. This addresses the main weaknesses of conventional GIC, which are its initial brittleness and susceptibility to moisture contamination or desiccation.

(AGD) Academy of General Dentistry Certification Practice Test

(AGD) Academy of General Dentistry Certification Practice Test

Free AGD Dental Materials and Application Questions and Answers