MDS PREP
What is the main disadvantage of using zinc phosphate cement?
1) Low compressive strength
2) Potential for pulpal irritation
3) Difficulty in removal
4) High cost
While it has good mechanical properties, poorly placed zinc phosphate cement can cause pulpal irritation.
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.
Which phase in high-copper amalgams is associated with the formation of CuCl23Cu(OH)2 as a corrosion product?
1) The ? (delt1) phase.
2) The ? (gamm1) phase.
3) The ? (epsilon) phase.
4) The ? (zet1) phase.
The n' phase in high-copper amalgams is associated with the formation of CuCl23Cu(OH)2.
What are microfilled composites known for?
1) Their high wear resistance.
2) Their high translucency.
3) Their ease of manipulation.
4) Both A and B.
Microfilled composites contain very fine silica particles (0.04 to 0.2 µm in diameter), which give them excellent translucency and a high surface area for better filling of small restorations.
What are the advantages of using Ormocers in dental restorations?
1) High elasticity and low thermal conductivity.
2) Low shrinkage and excellent biocompatibility.
3) Easy to manipulate and high modulus of elasticity.
4) Good radiopacity and high load deflection rate.
Ormocers have several advantages, including low shrinkage, excellent biocompatibility, and superior resistance to masticatory forces. These properties make them suitable for restorations that resemble natural teeth.
Which of the following is not a type of temporary cementing material?
1) Zinc oxide-eugenol (type III)
2) Calcium hydroxide
3) Glass ionomer cement (type 1)
4) Resin-modified glass ionomer cement
Resin-modified glass ionomer cement is not listed as a type of temporary cementing material in the text.
Modern dental noble metal casting alloys generally have equiaxed fine grain structures because of the incorporation of small amounts of
1) Chromium
2) Indium
3) Iridium
4) Palladium
Dental Materials Answer: 3
The term equiaxed refers to the fact that three dimensions of each grain are similar. In dendritic structure, grains are elongated. Dendritic micro structures are not desirable for cast dental alloys, reason being the inter dendritic regions can serve as sites for
crack propagation.
Addition of about 1 wt% of ruthenium, Iridium or rhenium as grain refiners makes modern dental noble metal casting alloys as equiaxed microstructures.
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.