MDS PREP
What is the primary advantage of using the frozen slab technique with zinc phosphate cement?
1) It increases the working time.
2) It decreases the setting time.
3) It increases the mechanical properties.
4) It changes the pH of the cement.
The frozen slab technique increases the working time of zinc phosphate cement by allowing more moisture to condense on the cool glass slab.
Epoxy resins are compatible with which of the following impression material :
1) Polysulphide impression material
2) Polyether impression material
3) Agar
4) Alginate
Dental Materials Answer: 2
Epoxy resins
· Abrasion resistance is many times greater than gypsum
· More expensive
· Undergoes 0.1 – 0.2% shrinkage, thus their shrinkage is approximately equal to gypsum. This is less of problem with newer formulations & polyurethane resin.
· Their detail reproduction is better.
· Hydrocolloids, polysulfides are not compatible with them.
What is Goldent, and how is it used in dental restorations?
1) A brand of gold alloy used for inlays and onlays
2) A form of gold foil with a high platinum content
3) A combination of powdered gold and gold foil in a pellet form
4) A gold-plated stainless steel mesh used for subgingival retention
Goldent is a form of direct gold restoration where pellets of powdered gold are wrapped in a No. 3 gold foil. The foil acts as a container for the gold particles and allows for better handling and condensation during placement. Each pellet contains approximately 95% powdered gold and 5% gold foil, making it more economical than using gold foil alone for restorations.
What is the typical setting time for gypsum-based products like dental plasters and stones?
1) Less than 10 minutes.
2) 10-30 minutes.
3) 30-60 minutes.
4) More than 60 minutes.
The setting time for gypsum products can range from a few minutes for impression plaster to up to 30 minutes for some dental stones, depending on the specific formulation and water to powder ratio.
What is the primary function of a dental sealer in restorative procedures?
1) To prevent microleakage
2) To desensitize the tooth
3) To enhance the aesthetics of the restoration
4) To reinforce the tooth structure
A dental sealer is used to fill the microscopic spaces between the restorative material and the tooth structure, primarily to prevent microleakage.
What is the significance of the direction of the applied force during condensation?
1) It is not important for the success of the restoration.
2) It affects the marginal integrity of the restoration.
3) It influences the adaptation of the material to the cavity walls.
4) It does not affect the physical properties of the restoration.
The significance of the direction of the applied force during condensation is that it affects the marginal integrity and adaptation of the material to the cavity walls. It is important to direct the force at an appropriate angle to ensure proper condensation and seating of the material.
What is the purity requirement for mercury in dental amalgams according to ANSI/ADA Specification No. 6?
1) It must be at least 99.9% pure.
2) It must be at least 99.0% pure.
3) It must be at least 95.0% pure.
4) It must be at least 90.0% pure.
Mercury that complies with the requirements of the United States Pharmacopoeia also meets requirements for purity in ANSI/ADA Specification No. 6, which is typically 99.9% pure.
What are the typical operating speeds for low-, medium-, and high-speed amalgamators?
1) 3000 to 3200 cpm for low-speed, 3500 to 3700 cpm for medium-speed, and 4000 to 4400 cpm for high-speed.
2) 3200 to 3400 cpm for low-speed, 3700 to 3800 cpm for medium-speed, and 4000 to 4400 cpm for high-speed.
3) 3000 to 3200 cpm for medium-speed, 3500 to 3700 cpm for high-speed, and 4000 to 4400 cpm for low-speed.
4) 3200 cpm for low-speed, 3700 cpm for medium-speed, and 4400 cpm for high-speed.
Low-speed amalgamators operate at 3200 to 3400 cpm, medium-speed at 3700 to 3800 cpm, and high-speed at 4000 to 4400 cpm.