MDS PREP
What is the liquefaction temperature of agar hydrocolloid?
1) 37°C - 50°C
2) 60°C - 70°C
3) 70°C - 100°C
4) 50°C - 65°C
Agar hydrocolloid must be heated to a liquefaction temperature between 70°C and 100°C to be suitable for impression taking.
What is the primary function of the eugenol in zinc oxide-eugenol cement?
1) To provide antimicrobial properties
2) To act as a plasticizer
3) To initiate the setting reaction
4) To increase the compressive strength
The eugenol in zinc oxide-eugenol cement acts as a plasticizer, providing temporary softness for easier manipulation.
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.
Before restoring a tooth with composite, the area is etched. Accidental contamination occurs with saliva, Therefore
1) the area is re-etched before restoration
2) the area is air-dried using an air spray and continue with restoring
3) wipe the saliva with cotton and continue to restore.
4) add excess composie material and cure it
Dental Materials Answer: 1
Etching of tooth surface with 37% phosphoric acid creates microporosities in the enamel and dentin. This is the main method of adhesion of composite resin to tooth surface.
After etching the surface energy of the enamel will increase. This will make it very sticky to any kind of contaminants. If salivary contamination will occur, the salivary proteins will precipitate in the microporosities. This will prevent the adequate penetration of the bonding agent, therby reducing the micotag formation. Hence, complete isolation is essential.
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 purpose of using a thermal insulating base?
1) To protect the pulp from thermal changes
2) To increase the strength of the restoration
3) To improve the aesthetics of the restoration
4) To facilitate the removal of the restoration
The purpose of a thermal insulating base is to protect the pulp from temperature changes during the placement of a restoration.
What is the typical average particle size of powered gold used in dental restorations?
1) 15 ?ms
2) 10 ?ms
3) 5 ?ms
4) 20 ?ms
The average particle size of powered gold used in dental restorations is 15 ?ms. This size allows for the gold to be manipulated and condensed properly within the cavity preparation to achieve the desired restorative outcome.
Modern dental noble metal casting alloys generally have equiaxed fine grain structures because of the incorporation of small amounts of
1) Chromium
2) Indium
3) Iridium
4) Palladium
Dental Materials Answer: 3
The term equiaxed refers to the fact that three dimensions of each grain are similar. In dendritic structure, grains are elongated. Dendritic micro structures are not desirable for cast dental alloys, reason being the inter dendritic regions can serve as sites for
crack propagation.
Addition of about 1 wt% of ruthenium, Iridium or rhenium as grain refiners makes modern dental noble metal casting alloys as equiaxed microstructures.