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.
Which of the following denture base materials has the highest linear shrinkage?
1) High-impact acrylic resin
2) Vinyl acrylic resin
3) Conventional acrylic resin
4) Rapid heat-cured acrylic resin
Rapid heat-cured acrylic resin has the highest linear shrinkage at 0.97%, which can affect the fit and stability of the denture.
What is the role of MDPB in dental composites?
1) It provides improved mechanical properties.
2) It acts as an initiator for the polymerization reaction.
3) It enhances the antibacterial activity of the composite material.
4) It reduces the viscosity of the resin.
MDPB (methacryloxy decyl pyridinium bromide) is a quaternary ammonium salt that has been shown to be effective against various streptococci in dental composites. Its inclusion enhances the antibacterial properties of the material.
What is the primary function of a light-curing unit in the polymerization of resin-based materials?
1) To generate heat for setting.
2) To activate the photosensitizer and initiate the polymerization reaction.
3) To accelerate the chemical reaction.
4) To increase the viscosity of the material.
Light-curing units emit light at specific wavelengths that are absorbed by the photosensitizer in the resin, triggering the free radical polymerization process and setting the material.
What is the dough-forming time for denture base resin according to ANSI/ADA Specification No. 12?
1) Less than 10 minutes
2) Less than 5 minutes
3) Less than 20 minutes
4) Less than 30 minutes
ANSI/ADA Specification No. 12 requires that the material should reach a doughlike consistency in less than 10 minutes from the start of the mixing process.
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 peak wavelength for light-activated dental composite resins?
1) 300-400 nm.
2) 400-500 nm.
3) 500-600 nm.
4) 600-700 nm.
Light-activated dental composite resins are usually cured with blue light at a peak wavelength of about 470 nm, which is absorbed by the photoinitiator, such as camphorquinone.
What is the purpose of adding barium sulfate to Gutta Percha?
1) To make it more radio-opaque
2) To improve thermal conductivity
3) To enhance the setting reaction
4) To act as a plasticizer
Barium sulfate is added to Gutta Percha to enhance its radiographic visibility.