MDS PREP
What is the relationship between the concentration of zinc and the setting expansion of an amalgam alloy?
1) A higher zinc concentration results in greater setting expansion.
2) A lower zinc concentration results in greater setting expansion.
3) There is no relationship between zinc concentration and setting expansion.
4) The relationship is not specified in the given text.
The relationship between zinc concentration and setting expansion is not specified in the given text. However, the presence of zinc in amalgams can affect the rate and extent of setting.
What is the mechanism of action for acid etching of dentin?
1) Formation of a smear layer.
2) Selective dissolution of hydroxyapatite crystals.
3) Dehydration of the dentin matrix.
4) Both A and B.
Acid etching selectively dissolves the hydroxyapatite crystals in dentin, creating microscopic tags and channels for resin infiltration, which enhances the bond between the restorative material and the tooth structure.
What is the role of a primer in the bonding process of resin cements?
1) To clean the tooth surface
2) To increase the surface energy of the tooth structure
3) To reduce the surface tension of the bonding agent
4) To accelerate the setting of the cement
A primer increases the surface energy of the tooth structure, enhancing the ability of the bonding agent to wet and infiltrate the surface.
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.
What are the main components of a typical dental composite resin?
1) Monomers, fillers, initiators, and accelerators.
2) Resins, fillers, catalysts, and diluents.
3) Polymers, pigments, and plasticizers.
4) Monomers, fillers, and cross-linking agents.
Dental composite resins typically consist of a resin matrix (monomers), filler particles (such as silica or glass), initiators (like camphorquinone), and accelerators (such as amines) to control the setting process.
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 the typical mixing time for temporary cementing materials?
1) 1-5 minutes
2) 5-15 minutes
3) 15-30 minutes
4) 1-15 minutes
The text does not specify the exact mixing time for temporary cements, but it states that the mixing time for all three varieties is approximately 1-15 minutes.
What is the typical polymer-to-monomer ratio required for denture base resin?
1) 1:1
2) 2:1
3) 3:1
4) 4:1
The accepted ratio of polymer to monomer for denture base resin is 3:1 volume, allowing sufficient wetting of the polymer particles.