MDS PREP
What is the primary mechanism of adhesion for resin cements?
1) Micromechanical retention
2) Chemical bonding
3) Physical adsorption
4) Ionic bonding
Resin cements primarily achieve adhesion through micromechanical retention and chemical bonding.
In which order do elastomeric impression materials rank in terms of tear strength?
1) Condensation silicone > Addition silicone > Polyether > Polysulfide
2) Polysulfide > Condensation silicone > Addition silicone > Polyether
3) Addition silicone > Condensation silicone > Polyether > Polysulfide
4) Polyether > Addition silicone > Condensation silicone > Polysulfide
Polysulfides generally have the highest tear strength among the elastomeric impression materials.
What are the typical mixing and setting times for zinc phosphate cement?
1) Mixing time: 1-2 minutes, Setting time: 5 minutes
2) Mixing time: 5-10 minutes, Setting time: 20 minutes
3) Mixing time: 1-15 minutes, Setting time: 1-2 minutes
4) Mixing time: 3-5 minutes, Setting time: 5-10 minutes
According to the text, the mixing time for zinc phosphate cement is about 1-15 minutes.
What is the primary concern with using zinc oxide-eugenol cement in large restorations?
1) Low compressive strength
2) Potential for pulpal toxicity
3) High thermal conductivity
4) High solubility
The primary concern is the potential for pulpal toxicity due to the diffusion of eugenol.
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.
Which material has the highest fracture toughness among the following?
1) Admixed amalgam
2) Light-cured glass ionomer
3) Hybrid composite
4) Cermet
Light-cured glass ionomer has a fracture toughness of 1.37 MPa.m%, which is higher than the other listed materials.
What does the term "A form" of Gutta Percha refer to?
1) At room temperature
2) After condensation
3) After heating to 56°C - 62°C
4) After mixing with Zinc Oxide
When heated to 56°C - 62°C, Gutta Percha gets converted to the A form, which is crucial for its expansion during the sealing process.
What is the effect of acid etching on dentin bond strength?
1) It decreases bond strength.
2) It has no effect on bond strength.
3) It increases bond strength.
4) It is unpredictable.
Acid etching of dentin creates a micro porous surface that allows for better infiltration and mechanical interlocking of the bonding agent, leading to improved bond strength between the restorative material and the tooth structure.