MDS PREP
What is the primary cause of delayed expansion in zinc-containing low-copper or high-copper amalgams?
1) Contamination by oxygen during trituration.
2) Contamination by water during trituration or condensation.
3) Over-trituration.
4) The presence of the ?2 phase.
A large expansion can take place if the amalgam is contaminated by moisture during trituration or condensation, known as delayed expansion or secondary expansion.
During crown cementation, complete filling of crown with cement is not advisable due to :
1) Increased risk of bubble entrapment
2) Increased seating time
3) Increased pressure required for seating crown
4) All of the above
Dental Materials Answer: 4
It is not advisable to fill the crown completely with cement due to following 4 reasons:
1. the time for removal of excess cement elevates.
2. the risk for bubble entrapment increases
3. increased pressure may be needed
4. the time for seating increases
What is the most corrodible phase in the low-copper amalgam system?
1) Sn7. Hg
2) ? (gamm1) phase
3) Cu3Sn phase
4) ? (delt1) phase
The Sn7. Hg or ? (gamm1) phase is the most corrodible in the low-copper amalgam system.
What is the primary function of a base material in dental restoration?
1) To seal the tooth from microleakage
2) To provide insulation from thermal changes
3) To reinforce the tooth structure
4) To enhance the aesthetics of the restoration
A base material in dental restoration is primarily used to provide a seal against microleakage.
What are the ideal requirements for a luting agent according to ANSI/ADA Specification No. 96 (ISO 9917)?
1) High compressive strength and long setting time
2) Low compressive strength and short setting time
3) High compressive strength and short setting time
4) Low compressive strength and long setting time
The text does not provide specifics on luting agent requirements in terms of compressive strength and setting time.
What is the classification of amalgam alloys based on zinc content?
1) Alloys with more than 0.01% zinc are classified as zinc-free, and those with less than 0.01% as zinc-containing.
2) Alloys with more than 0.01% zinc are classified as zinc-containing, and those with less than 0.01% as uno-zinc.
3) Alloys with more than 0.01% zinc are classified as high-zinc, and those with less than 0.01% as low-zinc.
4) Alloys with more than 0.01% zinc are classified as uno-zinc, and those with less than 0.01% as zinc-containing.
Alloys with more than 0.01% zinc are classified as zinc-containing, and those with less than 0.01% as uno-zinc.
What is the effect of pH on the bond strength of zinc polycarboxylate cement?
1) High pH increases bond strength.
2) Low pH increases bond strength.
3) pH has no effect on bond strength.
4) High pH decreases bond strength.
The bond strength is influenced by the acidity; a lower pH can enhance the bond strength.
What is hysteresis in the context of dental gels?
1) The difference between setting and working time
2) The difference between the temperature of gelation and liquification
3) The difference between the initial and final setting times
4) The difference between the maximum and minimum viscosities
Hysteresis in dental gels refers to the temperature lag or difference between the gelation temperature and the temperature at which the gel reverts back to a liquid state.