MDS PREP
What is the typical pH of zinc polycarboxylate cement immediately after mixing?
1) Less than 2
2) Between 2 and 4
3) Between 4 and 7
4) Greater than 7
The pH is mentioned to be around 2.8 after 3 minutes, which indicates an acidic nature initially.
What is the primary difference between the setting mechanism of light-cured and chemically cured composite resins?
1) Light-cured resins shrink towards the external surface, while chemically cured resins shrink towards the center.
2) Chemically cured resins require light activation.
3) Light-cured resins require a chemical catalyst.
4) There is no significant difference in the setting mechanism.
The setting mechanism of light-cured resins involves free radical polymerization initiated by light, which causes the material to contract away from the light source (typically the external surface).
What are the common types of water-based dental cements?
1) Zinc polycarboxylate
2) Calcium sulfate
3) Zinc oxide-eugenol
4) All of the above
Water-based cements include zinc polycarboxylate and calcium sulfate.
How do resin teeth typically bond with denture base resins?
1) Through mechanical undercuts.
2) Through silanization.
3) By forming chemical bonds.
4) Both A and B.
Resin teeth are capable of forming chemical bonds with commonly used denture base resins, which allows for a stronger and more durable bond compared to porcelain teeth.
What are the typical mixing and setting times for zinc phosphate cement?
1) Mixing time: 1-2 minutes, Setting time: 5 minutes
2) Mixing time: 5-10 minutes, Setting time: 20 minutes
3) Mixing time: 1-15 minutes, Setting time: 1-2 minutes
4) Mixing time: 3-5 minutes, Setting time: 5-10 minutes
According to the text, the mixing time for zinc phosphate cement is about 1-15 minutes.
Which type of amalgam alloy has the lowest compressive strength at 1 hour?
1) High-copper lathe-cut alloy
2) Low-copper lathe-cut alloy
3) High-copper spherical alloy
4) Low-copper spherical alloy
The compressive strength at 1 hour is lowest for the low-copper lathe-cut alloy, which is 45 MPa.
What are the stoichiometric formulas for the gamma (?), epsilon (?), and zeta (?) phases in dental amalgams?
1) ?: Ag3Sn, ?: Cu3Sn8, ?: Cu3Sn
2) ?: Ag3Sn, ?: AgSn, ?: CuSn
3) ?: AgSn, ?: Cu3Sn, ?: Ag3Sn8
4) ?: AgSn, ?: CuSn, ?: Ag3Sn.
?: Ag3Sn, ?: Cu3Sn8, ?: Cu3Sn
What is the typical film thickness for a resin cement?
1) 50 µm
2) 25 µm
3) 15 µm
4) 5 µm
Resin cements are generally applied in a film thickness of 25 µm or less for optimal performance.