CDT Dental Materials & Laboratory Techniques 1 — Questions and Answers

Question 1: What is the main purpose of dental waxes in the laboratory?

To serve as permanent restorations.
To create patterns and models for casting (Correct answer)
To clean dental instruments.
To disinfect impression materials.

Correct answer: To create patterns and models for casting

Dental waxes are fundamental in the laboratory for creating precise patterns of dental restorations like crowns, bridges, or partial denture frameworks. These wax patterns are then embedded in an investment material, and the wax is subsequently burned out. This 'lost wax technique' leaves a hollow mold, which is then filled with molten metal or ceramic to produce the final, accurately shaped dental appliance.

Question 2: Which material is commonly used for dental impressions?

Gold alloy.
Alginate (Correct answer)
Acrylic resin.
Porcelain.

Correct answer: Alginate

Alginate is a widely utilized impression material in dentistry due to its ease of use, cost-effectiveness, and ability to capture sufficient detail for many applications. It is an irreversible hydrocolloid that sets quickly, making it ideal for creating study models, orthodontic appliances, and preliminary impressions for dentures. While other materials exist, alginate remains a popular choice for general dental impressions.

Question 3: What is the purpose of using a dental articulator?

To measure tooth color.
To simulate jaw movements for accurate restoration alignment (Correct answer)
To sterilize dental models.
To harden impression materials.

Correct answer: To simulate jaw movements for accurate restoration alignment

A dental articulator is a mechanical device designed to simulate the movements of a patient's jaw. By mounting dental models on an articulator, technicians can accurately assess and adjust the occlusion (bite) of restorations such as crowns, bridges, or dentures. This ensures that the fabricated appliances fit correctly, function harmoniously with the patient's natural dentition, and prevent occlusal interferences.

Question 4: Why is burnout important in the casting process?

To cool the mold.
To remove wax and prepare the mold for casting (Correct answer)
To add strength to the wax.
To color the final restoration.

Correct answer: To remove wax and prepare the mold for casting

Burnout is a critical step in the lost wax casting technique, where the invested wax pattern is heated in a furnace to high temperatures. This process completely vaporizes the wax, leaving a clean, hollow cavity within the investment mold that precisely replicates the original wax pattern. The empty mold is then ready to receive molten metal, ensuring an accurate and contaminant-free casting for the final restoration.

Question 5: What is the main advantage of using porcelain for dental crowns?

High flexibility.
Superior aesthetics and translucency (Correct answer)
Extreme toughness.
Easy reshaping after cementation.

Correct answer: Superior aesthetics and translucency

Porcelain is highly valued in dentistry for its exceptional aesthetic qualities and translucency, allowing it to closely mimic the natural appearance of tooth enamel. This makes porcelain crowns virtually indistinguishable from natural teeth, especially in visible areas of the mouth. While other materials offer strength, porcelain excels in providing a lifelike and aesthetically pleasing restoration.

Question 6: What is the function of gypsum products in dental labs?

To etch tooth enamel.
To fabricate precise dental models (Correct answer)
To bond orthodontic brackets.
To polish restorations.

Correct answer: To fabricate precise dental models

Gypsum products, such as dental plaster and stone, are indispensable in dental laboratories for fabricating accurate positive reproductions (models) from dental impressions. These precise models serve as working casts for the construction of various dental appliances, including crowns, bridges, dentures, and orthodontic devices. Their ability to set hard and capture fine anatomical details is crucial for the precision required in lab work.

Question 7: Which metal is commonly used in dental casting alloys?

Aluminum.
Cobalt-chromium (Correct answer)
Lead.
Iron.

Correct answer: Cobalt-chromium

Cobalt-chromium alloys are extensively used in dentistry for casting partial denture frameworks and certain types of crowns. These alloys are favored for their excellent strength, rigidity, and superior corrosion resistance, making them highly durable and long-lasting. They are also biocompatible, providing a reliable and stable foundation for dental prosthetics.

Question 8: Why is investment material used in the casting process?

To polish restorations.
To create a heat-resistant mold for metal casting (Correct answer)
To reduce metal weight.
To cool down castings quickly.

Correct answer: To create a heat-resistant mold for metal casting

Investment material is a specialized refractory material that surrounds the wax pattern during the casting process. Its primary function is to create a strong, heat-resistant mold capable of withstanding the extreme temperatures of the burnout process and the subsequent injection of molten metal. This ensures the mold maintains its integrity and shape, allowing for an accurate and precise metal casting that replicates the original wax pattern.

Question 9: What safety precaution is essential when using rotary instruments?

Use bare hands for better grip.
Wear eye protection to prevent injury from debris (Correct answer)
Increase speed beyond limits.
Work without ventilation.

Correct answer: Wear eye protection to prevent injury from debris

When using rotary instruments, such as dental handpieces or lab grinders, high-speed debris, dust, and aerosols are generated, posing a significant risk of eye injury. Wearing appropriate eye protection, like safety glasses or a face shield, is therefore essential to safeguard the eyes from these projectiles. This critical safety precaution protects the technician from potential harm and ensures a safe working environment.

CDT Dental Materials & Laboratory Techniques 1

What is the main purpose of dental waxes in the laboratory?