Final Flashcards
What to know when using the tofflemire?
- wider side to occlusal
- narrower side toward gingival
- use wedges
- slot towards gingival
4 components of amalgam and their purpose/%
Silver: 40-70%, strength
Tin: 26-30%, decrease expansion
Copper: 2-30%, strengthen, corrosion resist, less creep
Zinc: 0-1%, O2 scavenger during manufacture, less brittle
Mercury: liquid
What is tensile force?
tensile refers to pulling force (typically the weakest)
Burs with rounded heads
1/4 - 10, 330 to 333, 245
Burs that leave a sharp line angle
inverted cone, straight fis (56, 57, 557), Tapered fis (169)
What bacteria are most responsible for caries?
-strep mutans
What does strep sanguis and strep mitis cause?
associated with healthy oral flora
What does bacteriodes melaningenicus cause?
perio disease
What is unsupported enamel?
When enamel rods are not supported by sound dentin. Why we diverge and bevel.
Which walls of a buccal pit prep should be converged and which diverged?
Converged: mesio-occlusal, disto-occlusal, and gingival
Diverged: NONE
**occlusal most wall of prep should be neither converged nor diverged
What walls in an occlusal prep should be converged vs diverged?
Converged: buccal and lingual walls of isthmuses
Diverged: distal and mesial walls of dovetails, termination of buccal and lingual grooves
How much convergence should the buccal and lingual walls of a box be?
3-4 degrees
When should you cap a cusp?
When the margin exceeds 2/3 the distance between teh groove and the cusp tip
How deep should an occlusal prep be for amalgam?
minimum 1.5 mm
How deep should an occlusal prep be for gold?
1-2 mm
How deep should an occlusal prep be for porcelain?
minimum 2 mm
While the depth of an occlusal amalgam prep should be at least 1.5 mm (for retention and strength of restoration) how deep into the dentin should the prep go?
0.2 - 0.5 mm deep into dentin
What is a common defect in class II amalgam restorations?
Failure of the margin due to insufficient condensing or too large of an increment
What is plastic deformation?
when strain is removed, the shape of the material remains changed
What is elastic deformation?
when force is applied to a material, it deforms, but when the force is removed, it retains its original shape
How are plastic deformation and elasticity related?
Plastic deformation occurs when the force applied to a material causes strain that is greater than the material’s elastic modulus.
What is the minimum thickness of dentin between the pulp and pulpal floor?
2 mm
Amalgam Creep
- What factors influence it?
- Correlated to ______ margins.
- Cu content has what affect?
- What phase is prone to creep?
- Time, temperature, strain
- ditched
- low copper = more creep
- Gamma 2 Phase
What is the most important factor affecting pulpal response?
Closeness of prep to pulp