MDS PREP
What is the typical setting time range for Type II (Normal set) alginate impression material?
1) 1-2 minutes
2) 2-4 minutes
3) 4-6 minutes
4) 6-8 minutes
Type II (Normal set) alginate impression material has a setting time of 2-4 minutes, which is longer than the fast-setting Type I material.
What is the volume polymerization shrinkage of ORMOCER?
1) 3.75 pounds
2) 0.04-0.4 µm
3) 0.1 – 0.01 µm
4) 1.97%
ORMOCER undergoes 1.97% by volume polymerization shrinkage, which is significantly less than that of conventional resin-based filling materials. This low shrinkage is one of the advantages of using Ormocers.
What are the main components of a typical dental composite resin?
1) Monomers, fillers, initiators, and accelerators.
2) Resins, fillers, catalysts, and diluents.
3) Polymers, pigments, and plasticizers.
4) Monomers, fillers, and cross-linking agents.
Dental composite resins typically consist of a resin matrix (monomers), filler particles (such as silica or glass), initiators (like camphorquinone), and accelerators (such as amines) to control the setting process.
How does the concentration of mercury in urine relate to neurological changes?
1) Neurological changes are detected at urine mercury levels of 1 µg/L.
2) Neurological changes are detected at urine mercury levels of 10 µg/L.
3) Neurological changes are detected at urine mercury levels of 500 µg/L.
4) There is no established link between mercury concentration in urine and neurological changes.
Neurological changes are not detected until urine mercury levels exceed 500 µg/L, which is significantly higher than the levels associated with amalgam placement.
What are the requirements for a good temporary cementing agent?
1) High compressive strength and good thermal conductivity
2) Low compressive strength and good thermal conductivity
3) High compressive strength and low thermal conductivity
4) Low compressive strength and low thermal conductivity
The ideal requirements for temporary cements include promoting the healing process and having a low compressive strength to facilitate removal.
What is the elastic limit of a wire, and what happens when a wire is deflected beyond this point?
1) The elastic limit is the point at which the wire begins to deform plastically.
2) The elastic limit is the force needed to permanently deform a wire.
3) The elastic limit is the maximum force a wire can withstand before fracture.
4) The elastic limit is the point at which a wire will always return to its original shape regardless of the force applied.
The elastic limit, also known as the yield strength, is the point at which a wire starts to undergo permanent deformation. When a wire is deflected beyond this point, it does not return to its original shape completely.
What is the preferred method of degassing for powered gold restorations?
1) An alcohol flame
2) An oxygen-acetylene flame
3) A butane flame
4) A nitrogen-hydrogen flame
The preferred method for degassing powered gold restorations is the use of an alcohol flame, specifically one that is a clean blue flame from absolute or 90% ethyl/methyl alcohol. The material is held in the flame until it reaches a dull red glow, which typically takes 15-20 seconds. This process removes any trapped air or volatile components that could compromise the integrity of the restoration.
What is the significance of the load deflection rate in orthodontic wires?
1) Low load deflection wires are preferred for large tooth movements.
2) High load deflection wires are preferred for large tooth movements.
3) The load deflection rate does not affect wire selection.
4) The load deflection rate determines the force applied during wire bending.
In orthodontics, wires with a low load deflection rate are typically preferred for areas requiring large tooth movements because they provide a more constant force as the tooth moves and the appliance is deactivated. This constant force is beneficial for controlling the rate of tooth movement.