MDS PREP
What happens if the water temperature exceeds 50°C during the mixing of gypsum products?
1) The setting reaction is accelerated.
2) The setting reaction is retarded.
3) No reaction occurs.
4) The material becomes less soluble.
If the temperature of the water used to mix gypsum products exceeds 50°C, it can slow down the setting reaction due to the reversible nature of the gypsum crystal formation at higher temperatures.
What is the effect of over- or under-triturating amalgam on its compressive and tensile strength?
1) Over-triturating increases both compressive and tensile strength in all amalgams.
2) Under-triturating increases both compressive and tensile strength in all amalgams.
3) Over-triturating decreases both compressive and tensile strength in all amalgams.
4) Over-triturating increases creep and under-triturating decreases it.
Over-triturating increases creep, and under-triturating lowers it.
What are the general ideal requirements for a temporary restorative material?
1) High compressive strength and good thermal conductivity
2) Low compressive strength and good thermal conductivity
3) High compressive strength and good marginal sealing
4) Low compressive strength and good marginal sealing
Temporary restorative materials should have low compressive strength (less than 35 MP1) and good marginal sealing to facilitate easy removal and minimize thermal microleakage.
What are the main advantages of using light-cured resins over chemically cured resins?
1) Less shrinkage, better aesthetics, and improved bond strength.
2) Lower cost and less sensitivity to moisture.
3) Faster setting and less technique sensitive.
4) Both A and C.
Light-cured resins generally have less shrinkage and are more aesthetically pleasing due to their ability to be polymerized to a higher degree. They also offer improved bond strength compared to chemically cured resins.
What is the primary function of 2-hydroxyethyl methacrylate (HEMA) in dentinal bonding?
1) To act as an initiator for the polymerization reaction
2) To create a hydrophobic barrier between dentin and resin
3) To dissolve the dentin surface
4) To create a hydrophilic bridge between the dentin and resin
HEMA is a hydrophilic monomer that is applied to the conditioned dentin. It fills the dentinal tubules and adheres to the exposed collagen fibers, creating a wetting layer that allows subsequent hydrophobic resins to infiltrate and bond to the dentin. This bridging action is crucial for the adhesion of resin to the hydrophilic dentin surface, which is essential for the longevity and durability of the restoration.
How does the elastic range of a wire affect its ability to be activated in orthodontic appliances?
1) A high elastic range allows for greater activation without causing permanent deformation.
2) A low elastic range allows for more precise and controlled activation.
3) The elastic range does not affect wire activation; it is only dependent on the force applied.
4) A wire with a high elastic range is more prone to permanent deformation during activation.
The elastic range of a wire determines the extent to which it can be deflected and still return to its original shape without permanent deformation. A wire with a high elastic range can be activated to a greater extent before it reaches its plastic range, making it suitable for larger tooth movements.
What are Compomers also known as, and what are their key characteristics?
1) Compomers are also known as Polyacrylic acid Modified Composite Resins (PMCRs), which are soft, non-sticky, and do not require mixing. They are known for their user-friendly nature and are a blend of Glass ionomers and Composite resins.
2) Compomers are also known as Glass-ionomer reinforced composites, which are hard, require mixing, and are difficult to place.
3) Compomers are a type of metal-reinforced composite that is used for inlays and onlays.
4) Compomers are a combination of Amalgam and Composite materials that provide high strength and aesthetics.
Compomers are indeed known as Polyacrylic acid Modified Composite Resins (PMCRs). They are characterized by their ease of placement, minimal shrinkage, and ability to be shaped and polished after curing. These properties make them a popular choice for dentists due to their user-friendliness and good handling characteristics.
What is the typical polymer-to-monomer ratio required for denture base resin?
1) 1:1
2) 2:1
3) 3:1
4) 4:1
The accepted ratio of polymer to monomer for denture base resin is 3:1 volume, allowing sufficient wetting of the polymer particles.