MDS PREP
What is the maximum allowable level of mercury in the blood according to the given information?
1) 1 µg/L
2) 3 µg/L
3) 5 µg/L
4) 10 µg/L
The maximum allowable level of mercury in the blood is specifically mentioned as 3 µg/L in the provided text.
What is the typical setting expansion of a high expansion dental stone?
1) Less than 0.1%.
2) 0.1-0.2%.
3) 0.2-0.3%.
4) More than 0.3%.
High expansion dental stones are designed to expand more than typical dental stones to compensate for the contraction of other materials and ensure a precise fit for restorations.
What are the main components of a typical dental composite resin?
1) Monomers, fillers, initiators, and accelerators.
2) Resins, fillers, catalysts, and diluents.
3) Polymers, pigments, and plasticizers.
4) Monomers, fillers, and cross-linking agents.
Dental composite resins typically consist of a resin matrix (monomers), filler particles (such as silica or glass), initiators (like camphorquinone), and accelerators (such as amines) to control the setting process.
What is the volume polymerization shrinkage of ORMOCER?
1) 3.75 pounds
2) 0.04-0.4 µm
3) 0.1 – 0.01 µm
4) 1.97%
ORMOCER undergoes 1.97% by volume polymerization shrinkage, which is significantly less than that of conventional resin-based filling materials. This low shrinkage is one of the advantages of using Ormocers.
What is the classification of amalgam alloys based on zinc content?
1) Alloys with more than 0.01% zinc are classified as zinc-free, and those with less than 0.01% as zinc-containing.
2) Alloys with more than 0.01% zinc are classified as zinc-containing, and those with less than 0.01% as uno-zinc.
3) Alloys with more than 0.01% zinc are classified as high-zinc, and those with less than 0.01% as low-zinc.
4) Alloys with more than 0.01% zinc are classified as uno-zinc, and those with less than 0.01% as zinc-containing.
Alloys with more than 0.01% zinc are classified as zinc-containing, and those with less than 0.01% as uno-zinc.
The function of 2% potassium sulphate in a gypsum product is
1) to regulate the setting expansion.
2) to regulate the setting time.
3) to act as a retarder.
4) none of the above.
Dental Materials Answer: 4
Sodium chloride is an accelerator up to about 2% of the hemihydrates, but at a higher concentration, it acts as a retarder. Sodium sulphate has its maximum acceleration effect at approximately 3.4%; at greater concentrations, it becomes a retarder.
The most commonly used accelerator is potassium sulphate. It is particularly effective in concentrations higher than 2% since the reaction product. which seems to be syngenite (K,Ca[SO4].H1O) crystallizes rapidly. Many soluble sulphates act as accelerators, whereas powdered gypsum (calcium sulphate dehydrate) accelerates the setting rate, because the
particles act as nuclei of crystallization.
Citrates. acetates and borates generally retard the reaction.
What is the primary disadvantage of using zinc oxide-eugenol as a permanent cement?
1) Low compressive strength
2) Shrinkage during setting
3) Difficulty in achieving a precise fit
4) Potential toxicity
While great for temporary cementation, its primary disadvantage for permanent use is its potential to cause tooth discoloration and pulpal irritation.
What is the primary advantage of using the frozen slab technique with zinc phosphate cement?
1) It increases the working time.
2) It decreases the setting time.
3) It increases the mechanical properties.
4) It changes the pH of the cement.
The frozen slab technique increases the working time of zinc phosphate cement by allowing more moisture to condense on the cool glass slab.