part 2 Flashcards
What is the significance of slight delayed expansion in dental materials?
It may contribute to retention of the material.
What are the clinical significance of excessive expansion due to moisture in dental materials?
- Post-op pain
- Cracked tooth
- Extrusion of amalgam from the cavity
- Decreased strength
- Increased corrosion
How does the strength of dental amalgam develop over time?
80% in 8 hours and final strength in 24 hours.
What is the relationship between the amount of mercury in the matrix and the strength of the restoration?
Less strength if more than 52% mercury.
When does the setting time of dental amalgam start?
During trituration and progresses with condensation and carving.
What factor relates to the plasticity of dental amalgam?
The technique employed to condense amalgam.
What is the effect of low plasticity on the condensing force required for amalgam restoration?
It requires greater condensing force for a good restoration.
What factors influence corrosion and tarnish in dental materials?
- Technique during manipulation
- Oral environment
- Oral hygiene
- Type of alloy
Define tarnish in the context of dental materials.
Surface alteration or discoloration.
What is corrosion in dental materials?
Total degradation of the restorative material.
What is tensile strength?
Force which resists deformation caused by a load that tends to stretch or elongate a body.
How does high mercury content (>52%) affect tensile strength?
Tensile strength is decreased.
What are two ways to increase tensile strength in dental amalgam?
- A butt joint of 90 degrees with the margin
- Use a fine cut alloy
What is thermal conductivity in relation to dental materials?
Ability of the material to conduct or transmit thermal changes.
How does amalgam rank in terms of thermal conductivity?
Amalgam has a high thermal conductivity.
List the three basic types of amalgam alloy.
- Conventional amalgam alloy
- Spherical alloys
- Dispersalloy
What is another name for conventional amalgam alloy?
Lathe-cut alloy.
What are the characteristics of conventional amalgam alloy?
- Rough surface finish
- Requires more mercury to wet the alloy particles
- Higher compressive strength than spherical alloy
What are the characteristics of spherical alloy?
- Very fine compared to conventional alloys
- Gives a very smooth surface finish
- Requires less mercury to wet the alloy particles
- Inferior compressive strength than conventional alloy
