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1 Dental Materials
What is the primary mechanism of bonding for resin-modified glass ionomer cements?1) Micromechanical retention2) Chemical bonding to tooth structure3) Ionic bonding4) Physical adsorption
Resin-modified glass ionomer cements bond through micromechanical retention and chemical bonding.
2 Dental Materials
What is the elastic limit of a wire?
1) The point at which the wire returns to its original shape.2) The point at which the wire starts to weaken.3) The point at which the wire yields permanently.4) The point at which the wire breaks.
The elastic limit of a wire is the point at which it yields permanently, meaning any greater force applied will result in irreversible deformation.
3 Dental Materials
Polyethers are susceptible to dimensional change if immersed for a long time. The recommended maximum time to immerse in disinfectant is
1) 1 minute 2) 10 minutes 3) 30 minutes 4) 1 hour
The polyethers are susceptible to dimensional change if immersed for a long time (>10 min) because of their pronounced hydrophilic nature.
4 Dental Materials
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 together2) It creates a chemical bond between the filler and the matrix3) It enhances the mechanical strength of the composite4) 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.
5 Dental Materials
What is the typical compressive strength of hardened ZnOE impression paste?1) 0.4-0.7 MPa2) 7 MPa3) 245 MPa4) 32 MPa
The compressive strength of hardened zinc oxide eugenol (ZnOE) impression paste is generally about 7 MPa, indicating its ability to withstand compressive forces without deformation or failure.
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