MDS PREP
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 gold foil in a direct gold restoration?
1) To provide a rigid framework for the powdered gold
2) To enhance the aesthetic appeal of the restoration
3) To improve the adhesion of the gold to the tooth structure
4) To act as a barrier between the gold and the oral environment
Gold foil is used in direct gold restorations to create a three-dimensional structure that can hold the loosely bound powdered gold in place. The foil acts as a container and facilitates the condensation of the gold particles into a cohesive mass, which is then adapted to the prepared cavity.
What is the effect of adding potassium sulfate to gypsum-based materials?
1) It accelerates the setting reaction.
2) It retards the setting reaction.
3) It increases the porosity.
4) It has no effect on the setting reaction.
Potassium sulfate acts as an accelerator by increasing the solubility of the hemihydrate and promoting the formation of dihydrate, which speeds up the setting process.
What is the primary cause of delayed expansion in zinc-containing low-copper or high-copper amalgams?
1) Contamination by oxygen during trituration.
2) Contamination by water during trituration or condensation.
3) Over-trituration.
4) The presence of the ?2 phase.
A large expansion can take place if the amalgam is contaminated by moisture during trituration or condensation, known as delayed expansion or secondary expansion.
What is the typical composition of Zinc Oxide-Eugenol Cement?
1) Zinc oxide and polyacrylic acid
2) Zinc oxide and eugenol
3) Zinc phosphate and polyacrylic acid
4) Zinc oxide and sodium silicate
Zinc Oxide-Eugenol Cement is primarily composed of zinc oxide and eugenol, with a pH of approximately 7, making it less irritating to pulpal tissues.
What is the primary use of zinc oxide-eugenol (type III) temporary cement?
1) For permanent cementation
2) For immediate post-operative treatment of sensitivity
3) For long-term temporary cementation
4) For trial of the metal framework
The general use of type III zinc oxide-eugenol temporary cement is for immediate post-operative treatment of sensitivity and to reduce post-operative sensitivity before placing a permanent restoration.
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 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.