MDS PREP
What is the primary advantage of zinc polycarboxylate cement?
1) High thermal conductivity
2) Low film thickness requirement
3) Chemical bonding with tooth structure
4) Fast setting time
Zinc polycarboxylate cement was formulated to have the strength of zinc phosphate and the biological acceptability of zinc oxide-eugenol cements, with the added advantage of chemical bonding to tooth structure.
What is the pH of zinc polycarboxylate cement after 28 days?
1) 2.8
2) 3.7
3) 5.2
4) 5.8
The pH values provided in the text indicate that zinc polycarboxylate cement reaches a pH of 5.8 after 28 days.
Gypsum Bonded Investment should NOT be heated above
1) 700°C
2) 750°C
3) 800°C
4) 900°C
Dental Materials Answer: 1
What is the typical particle size of silica in microfilled composites?
1) 0.5-1 µm.
2) 0.04-0.2 µm.
3) 1-10 µm.
4) 10-30 µm.
Microfilled composites have a very high surface area with silica particles diameters of 0.04 to 0.2 µm, which provides excellent aesthetic results and polishability.
Which type of composite has a filler particle size of 8-12 µm?
1) Microfilled composite
2) Small particle composite
3) Conventional composite
4) Hybrid composite
Conventional composites have a filler particle size of 8-12 µm. Microfilled composites have smaller particles (0.04-0.4 µm), small particle composites have intermediate sizes (1-5 µm), and hybrid composites have even smaller sizes (0.1-0.01 µm).
What is the typical refractive index range of bis-GMA and TEGDMA, and what happens when they are mixed in equal proportions?
1) 1.50 to 1.60 and increases.
2) 1.40 to 1.60 and decreases.
3) 1.55 for bis-GMA and 1.46 for TEGDMA, and a mixture yields approximately 1.50.
4) 1.50 for bis-GMA and 1.60 for TEGDMA, and a mixture yields approximately 1.55.
The refractive indices of bis-GMA and TEGDMA are approximately 1.55 and 1.46, respectively, and when mixed in equal proportions, they provide a refractive index of around 1.50.
What is the typical setting expansion of a regular dental stone?
1) Less than 0.1%.
2) 0.1-0.2%.
3) 0.2-0.3%.
4) More than 0.3%.
Regular dental stones have a low expansion rate, usually between 0.1% and 0.2%, which is suitable for accurate model fabrication.
What is the mechanism of action for acid etching of dentin?
1) Formation of a smear layer.
2) Selective dissolution of hydroxyapatite crystals.
3) Dehydration of the dentin matrix.
4) Both A and B.
Acid etching selectively dissolves the hydroxyapatite crystals in dentin, creating microscopic tags and channels for resin infiltration, which enhances the bond between the restorative material and the tooth structure.