Operative Flashcards
Initial colonizing bacteria
gram positive, facultative -> actinomyces viscosus, strep sanguinis
What material forms the hybrid layer?
silane
What is the primary photo initiator in most composite resins? What wavelength does it absorb photons primarily?
camphoroquinone, 470 nm
What is the initiator used in chemical or self-cure composites?
Benzoyl peroxide
At what pH does demineralization of hydroxyapatite enamel occur?
5.5
At what pH does the demineralization of dentin occur?
6.2
At what pH does the demineralization of hydroxyfluoroapatite occur?
4.5
What is the mechanism of action of CaOH?
induces dentin bridge formation within the dentin pulp complex
What are the 2 main functions of primer?
- infiltrate and remove water from enamel prisms, dentin tubules, and exposed collagen network
- form the hybrid layer
How is the hybrid layer formed?
ETCH removes smear layer, exposes collagen network, then PRIMER penetrates and allows adhesive resin to form micro tags
The number and diameter of dentinal tubules ___ closer to the pulp.
increases
The ___ phase decreases the strength of amalgam.
Gamma 2
How do we avoid a decrease in strength of amalgam and why does that work?
Condensing, which brings excess mercury to the surface of the amalgam to be removed.
What is a property unique to amalgam and has to do with marginal sealing?
Amalgam is the only restorative material that improves its marginal seal with age.
What is the point of trituration of amalgam?
Remove the oxide coating and wet each particle of the alloy with mercury
What are the optimal water levels of fluoride?
0.7-1.2 ppm (mg/L)
Rank tooth colored restorations in order of decreasing fluoride release:
GI > RMGI > compomers > composite resin
Fracture toughness is?
the material’s ability to resist propagation of a crack
How can the setting time of ZOE be accelerated?
add water
Amalgam contains what metals?
Mercury, silver, copper, tin
Why is zinc added to amalgam? (4)
- prevents oxidation of other metals in the alloy, (amalgam doesn’t darken)
- enhances mechanical properties
- reduces marginal fracture rate
- prolongs the life
True or false: overmixing amalgam reduces its strength.
FALSE
What bacteria primarily cause root caries?
Actinomyces viscosus
Which bacteria is associated with dental caries?
Strep mutans
which phase of amalgam is the weakest?
gamma 2
What is the half life of mercury in the human body?
55 days
What is the dental hand instrument formula?
1- width of blade
2- if present, primary cutting angle
3- length of blade
4- blade angle
How does amalgam set up?
mercury reacts with silver on or in the alloy particles
What is eburnated dentin?
sclerotic dentin, appears dark from extrinsic staining, is firm, is seen in older patients
The additional resin in RMGIs compared to conventional GIs causes what disadvantage?
increased thermal expansion
The most common cause of fracture at the isthmus of a class II restoration is:
sharp axio-pulpal line angle
What is the most important factor of a preparation that affects the pulpal response?
remaining dentinal thickness (RDT)
What polishers are good for amalgam?
Prophy cup + tin oxide
Abrasive-impregnated rubber points
Sof-lex disks
Over-condensing amalgam will lead to?
chipping and flaking during carving
prolonged condensation of amalgam causes?
decreased strength
Silicate cements are not good for ____ restorations because _____.
inter proximal, easily wear
Minimum number of flutes a carbide bur needs to be considered “finishing”?
12
Strongest phase of amalgam?
gamma 1
Weakest phase of amalgam?
gamma 2
High noble metals have approximately what % gold?
40%
What primarily determines the character of teeth?
Texture of enamel
