MDS PREP
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.
VLC resins are also called
1) microwave-activated resins.
2) tertiary amine-activated resins.
3) light-activated resins.
4) heat-activated resins.
Dental Materials Answer: 3
The first light-activated systems were formulated for UV light to initiate free radicals. Today the UV light-cured composites have been replaced by visible blue-light-activated systems with greatly improved depth of cure, a controllable working time, and other advantages.
Because of these advantages, visibly light-activated composites are more widely used than are chemically acti wited materials.
What are the advantages of using light-cured composites over chemically cured products?
1) Less porosity, less staining, increased strength, enhanced color stability, and control of working time.
2) Faster curing time, better translucency, and less shrinkage.
3) Longer shelf life and lower cost.
4) Higher wear resistance and easier to manipulate.
Light-cured composites do not require mixing, which reduces porosity and staining. They also allow for better control over working time and increased color stability due to the use of aliphatic amines.
What is the typical concentration of camphorquinone used in dental composite resins?
1) 0.1 wt%.
2) 0.2 wt%.
3) 0.5 wt%.
4) 1.0 wt%.
Small quantities of camphorquinone, typically less than 0.2 wt%, are sufficient to initiate the polymerization process when the composite resin is exposed to blue light.
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.
Which of the following is a common cross-linking agent in poly (methyl methacrylate) denture base resins?
1) Glycol dimethacrylate
2) Benzoyl peroxide
3) Hydroquinone
4) Methyl methacrylate
Glycol dimethacrylate is commonly used as a cross-linking agent in poly (methyl methacrylate) denture base resins to enhance the material's strength and stability.
What is the ANSI/ADA Specification No. 96 (ISO 9917) minimum compressive strength for luting cement?
1) 50 MPa
2) 70 MPa
3) 100 MPa
4) 150 MPa
The ANSI/ADA Specification No. 96 (ISO 9917) stipulates a minimum 24-hour compressive strength of 70 MPa for standard luting consistency dental cement.
What is the primary advantage of using the frozen slab technique with zinc phosphate cement?
1) It increases the working time.
2) It decreases the setting time.
3) It increases the mechanical properties.
4) It changes the pH of the cement.
The frozen slab technique increases the working time of zinc phosphate cement by allowing more moisture to condense on the cool glass slab.