MDS PREP
What is the role of the silane-coupling agent in the bonding between the filler and matrix in a dental composite material?
1) It acts as a binder to physically hold the filler and matrix together
2) It creates a chemical bond between the filler and the matrix
3) It enhances the mechanical strength of the composite
4) It provides a smooth surface for the filler to be evenly distributed in the matrix
Silane-coupling agents are used to improve the bonding between filler particles and the matrix in dental composite materials. They contain a methacrylic group that can co-polymerize with the dimethacrylate monomers present in the matrix, while also having functional groups that can interact with the filler material, typically silica or glass particles. This dual interaction creates a chemical bond, which enhances the overall stability and strength of the composite material.
What is the primary component of zinc polycarboxylate cement?
1) Zinc oxide
2) Polyacrylic acid
3) Titanium dioxide
4) Calcium hydroxide
Zinc polycarboxylate cement primarily consists of zinc oxide and polyacrylic acid.
The point at which a stress of a material exhibits a specific limited deviation P Is called
1) Proportional limit
2) Tensile strength
3) Ultimate strength
4) Yield strength
Dental Materials Answer: 4
Yield strength is the stress required to produce plastic deformation.
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 sodium chloride as an accelerator in gypsum-based materials?
1) To increase the setting temperature.
2) To accelerate the setting reaction.
3) To improve the mechanical properties.
4) To prolong the working time.
Sodium chloride acts as an accelerator in gypsum-based materials by increasing the solubility of the hemihydrate, thereby speeding up the conversion to dihydrate and the overall setting process.
What is the structural formula of the substance found in irreversible hydrocolloid?
1) Anhydro-?-d-mannuronic acid
2) Anhydro-?-d-glucuronic acid
3) Anhydro-?-d-glucuronic acid
4) Anhydro-?-d-mannuronic acid
Irreversible hydrocolloid, such as alginate, is based on the structure of anhydro-?-d-mannuronic acid.
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.
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.