MDS PREP
What are the main properties of Compomers?
1) High elasticity and high load deflection rate.
2) High modulus of elasticity and low shrinkage.
3) Easy to inject, shape, and polish with good aesthetics.
4) High thermal conductivity and good radiopacity.
Compomers are known for their ease of use, being non-sticky, and simple to place and shape. They are a hybrid of glass ionomer and composite resin properties, offering good aesthetics and user-friendly handling.
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 type of dental cement is used in cases of rampant caries and unhygienic oral conditions?
1) Zinc polyacrylate
2) Calcium sulfate
3) Zinc oxide-eugenol
4) Calcium hydroxide
Calcium hydroxide is used in cases of rampant caries and unhygienic oral conditions due to its antibacterial and tissue-dissolving properties.
What is the primary concern with using zinc oxide-eugenol cement in large restorations?
1) Low compressive strength
2) Potential for pulpal toxicity
3) High thermal conductivity
4) High solubility
The primary concern is the potential for pulpal toxicity due to the diffusion of eugenol.
Brinnel hardness number of a dental gold alloy is directly proportional to its:
1) Tensile strength
2) Elongation
3) Modulus of elasticity
4) Modulus of resiLience
Dental Materials Answer: 1
Brinnel and Rockwell tests are cLassified as macrohardness tests and they aie not suitable for brittle materials.
The Knoop and Vickers tests are classified as microhardness tests. Both of these tests employ toads less than 9.8N.
The Shore and the Barcot tests are used for measuring the hardness of rubbers and plastics.
The Bnnnel test is the one of oldest tests used for determining the hardness of materials and is directly related to proportional limit and the ultimate tensile strength of dental gold alloys.
The convenience of the Rockwell test, with direct reading of the depth of the indentation, has lead to its wide usage.
The Knoop hardness test is used to obtain the values for both exceedingly hard and soft materials. The hardness value is independent of the ductility of the material.
The Vickers test is employed for dental costing gold alloys. It is suitable for determining the hardness of brittle materials.
Which of the following cements bonds to tooth structure, which has an anticariogenic effect, has a degree of translucency and does not irritate the pulp?
1) Polycarboxylate cement
2) Resin cement
3) Silicate Cement
4) Glass ionomer cement
Dental Materials Answer: 4
Chelation of carboxyl groups of the polyacids with the calcium in the apatite of enamel and dentin is the main mechanism through which glass ionomer bonds to tooth structure.
Glass ionomers release fluoride which results in the inhibiton of the progression of secondary caries. GIC is relatively biocompatable.
They elicit a greater pulp reaction as compared to ZnoE but generally less compared to zinc phosphate cement.
What is the typical polymerization shrinkage of Bis-GMA?
1) 1-2%.
2) 3-4%.
3) 5-6%.
4) 5%.
Bis-GMA undergoes a free radical addition polymerization reaction with a shrinkage of about 1-2%, forming a highly rigid cross-linked setting material.
What is the typical timeframe for the initiation of dimensional change measurement in an amalgam?
1) At the beginning of trituration.
2) Between 5 minutes and 24 hours after the beginning of trituration.
3) At the end of trituration.
4) 40 days after the restoration.
Dimensional change measurement is typically initiated between 5 minutes and 24 hours after the beginning of trituration.