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
What kind of caries is fluoride most affective against?
smooth surface caries
Capping weak cusps when the margin exceeds 2/3 distance between groove and cusp is called a ___________.
Resistance form
Slightly rounded corners/line angles and a flat floor are examples of ___________.
Resistance form
Sufficient thickness of a prep/restoration is an example of ____________.
amalgam 1.5+ mm
gold 1-2 mm
porcelain 2 mm
Resistance form
Bevels that remove unsupported enamel and reduce stress concentrations are examples of _______
resistance form
Wall length, convergence (for amalgam), and parallelism are examples of __________.
Retention form
What pH demineralizes enamel?
pH 5.5 and below
What pH demineralizes dentin?
pH 6.5 and below
What happens to pH after a sugar exposure?
pH remains below 5.5 for 20-60 minutes
Where do caries spread/advance most rapidly?
root surface because structure is softer there
What do sealants do/what caries do they prevent?
Fill in pits and fissures (prevent strep mutans from colonizing).
** Once colonized, carious lesion in 6-24 months.**
What is the most common form of caries in young patients with permanent dentition?
Smooth surface?
What are the 3 P’s?
- Posture
- Positioning
- Periodic Stretching
What is a Class I?
occlusal
What is a Class II?
proximal surfaces of premolars and molars
What is a Class III?
proximal surfaces of incisors and canines (WITHOUT the incisal edge)
What is a Class IV?
proximal surfaces of incisors and canines that DO INCLUDE the incisal edge
What is a Class V?
gingival 1/3 of smooth surfaces
What is a Class VI?
incisal edge or cusp
What are the two salivary enzymes?
Amylase: starches
Lingual lipase: lipids
What is ptyalin?
salivary amylase
Are direct pulp caps more successful around pulp horns or along an axial wall?
pulp horns
When is a Tofflemire matrix band needed?
Class 2 restorations
When is the Palodent system most useful?
small composite restorations
Rank the components of amalgam POWDER from greatest to least.
Ag > Sn > Cu > Zn
What type of force breaks brittle materials most easily?
Tensile forces (pulling/tearing)
When energy goes into changing the shape of some material and it stays changed, that is said to be ________________.
plastic deformation
When energy goes into changing the shape of some material and the material goes back to its original form, that is __________________.
elastic deformation
Mechanical energy is lost whenever an object undergoes ___________________.
plastic deformation.
What is the difference between a cavity liner, cement, or base>
Liner: thinnest
Cement: intermediate
Base: thickest
Amalgam is brittle in ______.
Small bulk
Amalgam has low ______.
tensile strength
Amalgam has high _______.
Compressive strength
A lesion extends into the middle 1/3 of enamel. How would you classify it?
E2 or RA2
A lesion extends into the outer 1/3 of enamel. How would you classify it?
D1
What can cause aspiration of odontoblasts in dentin tubules?
dehydration due to air blasts to exposed dentin
Heat build up from high speed hand pieces can cause ___________.
dead tracts
