MDS PREP
What are the general ideal requirements for a temporary restorative material?
1) High compressive strength and good thermal conductivity
2) Low compressive strength and good thermal conductivity
3) High compressive strength and good marginal sealing
4) Low compressive strength and good marginal sealing
Temporary restorative materials should have low compressive strength (less than 35 MP1) and good marginal sealing to facilitate easy removal and minimize thermal microleakage.
What is the primary purpose of using a thermal insulating base?
1) To protect the pulp from thermal changes
2) To increase the strength of the restoration
3) To improve the aesthetics of the restoration
4) To facilitate the removal of the restoration
The purpose of a thermal insulating base is to protect the pulp from temperature changes during the placement of a restoration.
The opacity in ceramics is achieved by adding
1) Boric oxide
2) Copper oxide
3) Silica
4) Titanium oxide
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.
Addition of carbon is contraindicated in which of the following investment materials :
1) Gypsum bonded
2) Silica bonded
3) Phosphate bonded
4) All
Dental Materials Answer: 3
Occurence of carbon contamination from investment can easily be observed in case casting temp. are high as seen in melting of high noble alloys for metal ceramic (eg. AgPd or Pd-Ag alloys) or base metal alloys.
Such contamination embrittles the alloy.
What is the maximum rate of acid erosion allowed for zinc polyacrylate cements according to ADA Specification No. 96?
1) 2.0 mm/hour
2) 4.0 mm/hour
3) 6.0 mm/hour
4) 8.0 mm/hour
The ADA specification sets a limit of 2.0 mm/hour for acid erosion to ensure the cement’s stability in the oral environment.
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.
Polyethers are susceptible to dimensional change if immersed for a long time. The recommended maximum time to immerse in disinfectant is
1) 1 minute
2) 10 minutes
3) 30 minutes
4) 1 hour
Dental Materials Answer: 2
The polyethers are susceptible to dimensional change if immersed for a long time (>10 min) because of their pronounced hydrophilic nature.