MDS PREP
What is the thermal property of GIC similar to?
1) Enamel
2) Dentin
3) Glass Ionomer
4) Zinc Oxide-Eugenol Cement
GIC has a thermal expansion coefficient of 13-16 PPM/°C which is quite close to the values of dentin (8-11 PPM/°C). This similarity helps in reducing marginal leakage.
What is the role of a primer in the bonding process of resin cements?
1) To clean the tooth surface
2) To increase the surface energy of the tooth structure
3) To reduce the surface tension of the bonding agent
4) To accelerate the setting of the cement
A primer increases the surface energy of the tooth structure, enhancing the ability of the bonding agent to wet and infiltrate the surface.
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 primary chemical bonding mechanism between etched enamel and restorative materials?
1) Formation of a smear layer.
2) Ionic bonding.
3) Covalent bonding.
4) Mechanical interlocking.
Acid etching creates microscopic tags and fissures on the enamel surface, allowing the restorative material to flow in and mechanically interlock, enhancing the bond strength.
What is the function of a light source in photopolymerization of dental composites?
1) To generate heat for setting.
2) To activate the photosensitizer and initiate the polymerization reaction.
3) To cure the material by chemical reaction.
4) To improve the aesthetics of the restoration.
The light source is crucial in the photopolymerization process as it activates the photosensitizer, usually camphorquinone, which in turn generates free radicals that initiate the polymerization of the resin.
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 typical concentration range of phosphoric acid used for enamel etching?
1) 10-20%
2) 20-30%
3) 30-40%
4) 35-50%
Phosphoric acid concentrations between 20% and 30% are commonly used for acid etching of enamel to create a roughened surface for mechanical bonding of restorative materials.
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.