Chapt 8 Impression Material

Question 1

Accelerator

Answer 1

A catalyst compound that speeds up the impression materials reaction.

Question 2

Addition reaction

Answer 2

A polymerization reaction, each polymer chain grows to a maximal length in sequence.

Question 3

Base paste (=base putty)

Answer 3

The main component that forms the three-dimensional structure of a final impression.

Question 4

Cast

Answer 4

A replicate of a part of the oral cavity or extraoral facial structures that is produced in a durable hard material.

Question 5

Catalyst paste (=catalyst putty)

Answer 5

A structural component of dental materials that initiates the polymerization reaction. Witch decreases the energy required for the polymerization reaction

Question 6

Colloid 膠體

Answer 6

A solid, liquid, or gaseous substance made up of large molecules or masses of smaller molecules that remain in suspension in a surrounding continuous medium of different matter.

Question 7

Thixotropy (觸變性)

Answer 7

The property of certain gels or fluids to become less viscous when sufficient energy in the form of impact force or vibration is applied to overcome its yield stress; at rest they require a specific time to return to the previos viscous state.The property of certain gels or fluids to become less viscous when sufficient energy in the form of impact force or vibration is applied to overcome its yield stress; at rest they require a specific time to return to the previous viscous state.

Both pseudoplasticity and thixotropy are shear thinning. processes; pseudoplastic viscosity is not time dependent as thixotropy.

Question 8

Undercuts

Answer 8

The recessed areas on dental structures, including teeth, edentulous ridges, prostheses, and restorations.

Question 9

Viscoelasticity

Answer 9

The ability of a material to strain instantaneously like an elastic solid during rapid stretching or to resist shear flow and to strain linearly over time (like honey) when a stress is applied slowly.