MDS PREP
What is the typical refractive index range of bis-GMA and TEGDMA, and what happens when they are mixed in equal proportions?
1) 1.50 to 1.60 and increases.
2) 1.40 to 1.60 and decreases.
3) 1.55 for bis-GMA and 1.46 for TEGDMA, and a mixture yields approximately 1.50.
4) 1.50 for bis-GMA and 1.60 for TEGDMA, and a mixture yields approximately 1.55.
The refractive indices of bis-GMA and TEGDMA are approximately 1.55 and 1.46, respectively, and when mixed in equal proportions, they provide a refractive index of around 1.50.
What is the minimum 24-hour compressive strength required for dental cement according to ANSI/ADA Specification No. 96 (ISO 9917)?
1) 50 MPa
2) 70 MPa
3) 100 MPa
4) 150 MPa
The text states that the standard luting consistency of dental cement must exhibit a minimum 24-hour compressive strength of 70 MPa.
What are the common types of water-based dental cements?
1) Zinc polycarboxylate
2) Calcium sulfate
3) Zinc oxide-eugenol
4) All of the above
Water-based cements include zinc polycarboxylate and calcium sulfate.
What is the primary difference between Class I and Class II gypsum products?
1) Setting time.
2) Compressive strength.
3) Expansion.
4) Both A and B.
Class II (dental stone) has a higher compressive strength compared to Class I (dental plaster), making it suitable for model making and other applications requiring higher durability.
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 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 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.
Which of the following statements about the dimensional change of amalgams is correct?
1) The low-copper, lathe-cut alloy has the highest dimensional change.
2) The high-copper admixed alloy has the lowest dimensional change.
3) All amalgams have a dimensional change of -19.7 �m/cm.
4) All amalgams have a dimensional change of -1.9 �m/cm.
The lowest change of -1.9 �m/cm was for the high-copper admixed alloy.