MDS PREP
What is the typical concentration of sodium chloride used as an accelerator in dental plaster?
1) 5%.
2) 10%.
3) 15%.
4) 20%.
A concentration of sodium chloride of about 5% is commonly added to dental plaster to accelerate the setting reaction and reduce the setting time.
What is the relationship between the concentration of zinc and the setting expansion of an amalgam alloy?
1) A higher zinc concentration results in greater setting expansion.
2) A lower zinc concentration results in greater setting expansion.
3) There is no relationship between zinc concentration and setting expansion.
4) The relationship is not specified in the given text.
The relationship between zinc concentration and setting expansion is not specified in the given text. However, the presence of zinc in amalgams can affect the rate and extent of setting.
What is the primary purpose of using an obtundent in dentistry?
1) To reduce post-operative sensitivity
2) To promote the healing process
3) To strengthen the tooth structure
4) To whiten the tooth
An obtundent is used to reduce post-operative sensitivity by sealing the dentinal tubules and protecting the pulp.
What is the typical pH of a resin cement immediately after mixing?
1) Less than 2
2) Between 2 and 4
3) Between 4 and 7
4) Greater than 7
The pH of resin cements is usually slightly acidic after mixing, subject to variation in formulation.
Which of the following statements is CORRECT about the optimal force magnitude recommended for condenser nibs of different diameters during the condensation of dental amalgam?
1) A force of 15 pounds is recommended for all condenser nibs regardless of their diameter.
2) A force of 3.75 pounds is recommended for condenser nibs of 0.5 mm diameter, 8.43 pounds for 0.75 mm, and 15 pounds for 1 mm diameter.
3) A force of 5 pounds is recommended for condenser nibs of all diameters.
4) The force magnitude should be adjusted according to the density of the dental amalgam alloy being used.
The optimal force magnitude recommended for condenser nibs of different diameters is based on the principle that a smaller diameter requires less force to achieve the same amount of condensation pressure at the bottom of the condenser. The given text states that 3.75 pounds are recommended for 0.5 mm, 8.43 pounds for 0.75 mm, and 15 pounds for 1 mm diameter nibs. This is to ensure proper condensation without exceeding the physiologic limits of the tooth.
What is the purpose of adding barium sulfate to Gutta Percha?
1) To make it more radio-opaque
2) To improve thermal conductivity
3) To enhance the setting reaction
4) To act as a plasticizer
Barium sulfate is added to Gutta Percha to enhance its radiographic visibility.
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.
What is the typical polymer-to-monomer ratio required for denture base resin?
1) 1:1
2) 2:1
3) 3:1
4) 4:1
The accepted ratio of polymer to monomer for denture base resin is 3:1 volume, allowing sufficient wetting of the polymer particles.