MDS PREP
What is the pH of zinc polycarboxylate cement after 28 days?
1) 2.8
2) 3.7
3) 5.2
4) 5.8
The pH values provided in the text indicate that zinc polycarboxylate cement reaches a pH of 5.8 after 28 days.
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 µm/cm.
4) All amalgams have a dimensional change of -1.9 µm/cm.
The lowest change of -1.9 µm/cm was for the high-copper admixed alloy.
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 preferred method of degassing for powered gold restorations?
1) An alcohol flame
2) An oxygen-acetylene flame
3) A butane flame
4) A nitrogen-hydrogen flame
The preferred method for degassing powered gold restorations is the use of an alcohol flame, specifically one that is a clean blue flame from absolute or 90% ethyl/methyl alcohol. The material is held in the flame until it reaches a dull red glow, which typically takes 15-20 seconds. This process removes any trapped air or volatile components that could compromise the integrity of the restoration.
What is the typical bond strength of etched enamel with restorative materials?
1) 5-10 MPa.
2) 15-25 MPa.
3) 5-10 MPa.
4) 30-50 MPa.
Properly etched enamel surfaces can achieve bond strengths of approximately 15 to 25 MPa when using suitable restorative materials.
What is the significance of the direction of the applied force during condensation?
1) It is not important for the success of the restoration.
2) It affects the marginal integrity of the restoration.
3) It influences the adaptation of the material to the cavity walls.
4) It does not affect the physical properties of the restoration.
The significance of the direction of the applied force during condensation is that it affects the marginal integrity and adaptation of the material to the cavity walls. It is important to direct the force at an appropriate angle to ensure proper condensation and seating of the material.
The opacity in ceramics is achieved by adding
1) Boric oxide
2) Copper oxide
3) Silica
4) Titanium oxide
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.