-
which two base metals are added to gold to increase harness?
copper and silver
-
why is it important for the modulus of elasticity (stiffness) of base metals be 2X more than gold based alloys?
for partial denture framework use
-
what are the two disadvantages of base metals?
- harder = hard to cut and polish
- higher casting temp = more cost for equip
-
what forms after metal cools post melting and casting?
crystals (grains)
-
which are more desirable in crystal formation, small or large grains?
small
-
what two components are added to gold-based alloys to keep crystals from growing too large?
iridium and ruthenium
-
what is annealing?
it can improve properties of ____-_____ alloys
-
annealing base-metal alloys will ______ the properties
degrade
-
what four components are added to form oxides on the metal to bond porcelain?
-
what is heated at high temp to form oxides on the surface when dealing with pfms?
substructure
-
porcelain ______ fuses to the oxide layer
CHEMICALLY
-
t/f there is a slight change in metal composition to withstand high heat of firing porcelain (turning into glass)
true
-
why is opaque porcelain placed on metal?
to hide color (keeps the oxide color from showing through the porcelain and the main color is used for the crown)
-
t/f less tooth reduction is necessary for porcelain than for full metal cast crowns
FALSE! MORE tooth reduction
-
the "coping" metal for a pfm is ___-___mm thick
0.3-0.5
-
what must the coping of a pfm be besides at least .3mm thick to prevent distortion at high temps?
-
what does the thickness of the porcelain need to be in order to obtain a solid structure for a crown?
1.5mm
-
what are the three types of porcelain alloys?
- high-noble
- noble
- base-metal
-
why do the metal and porcelain have compatible rates of thermal expansion?
to keep them from cracking
-
the tooth structure for a pfm must be reduced _____mm thick
1.8
-
what are the most common base metal alloys for removable prosthetic casting alloys? (2)
- chrome-cobalt
- nickel-chrome
- (chromium content that gives corrosive resistance of these)
-
____-fusing porcelains are used more because they produce less wear of opposing enamel than medium or high-fusing porcelains
LOW
-
t/f noble metals are more biocompatible with oral tissues
true
-
____ metals corrode less than base metals
noble
-
which corrosion products are responsible for allergic responses?
base metals
-
t/f higher allergy rate for a male compared to a female is 10:1
FALSE! for a FEMALE compared to a MALE is 10:1 (jewelry might be the factor that sensitizes them)
-
where would an allergic rxn to nickel in the oral cavity most likely be located?
around the free gingival tissues from a crown
-
t/f some rxns to nickel cause skin rxns even if it is coming from the mouth
true
-
what are solders used for?
to repair cast restorations (usually gold-based alloys)
-
what four things do gold-based solders do?
- join units of a bridge together
- add contacts
- close holes in the occlusal surface from grinding
- marginal deficiencies
-
the HIGHER fineness number of gold solder, the _______ the gold content, the ________ the melting point of the solder
-
______ is added to both gold & silver solders to lower the melting range
TIN
-
What kind of solder is used for orthodontics-fixed space maintainer components, solder wire components together
Pediatric Dentistry-space maintainer?
SILVER solder
-
Wrought alloy metals are formed _____ the metal is cast
AFTER
-
what are wrought metal alloys?
alloys that have been mechanically changed metal into another form
-
a wrought alloy metal is ______ and has a ________ yield strength than just an alloy
-
wrought metal alloys may be annealed (heat modified) to create what?
resistance to deformity
-
t/f overheating a wrought metal alloy can degrade the properties of the metal
true
-
what kind of wire is used for clasps of a removable prosthesis?
wrought
-
which wire is used for ortho arch wires?
wrought
-
_______ wires in ortho or oral surgery are made out of wrought metal
ligature
-
endodontic files and reamers are made out of what type of wire?
wrought wire
-
what is it in an arch wire that exerts the forces that move the teeth?
the "memory"
-
what creates memory in the wire so it tries to reassume its original shape?
resistance to deformity
-
Arch wire held to ortho bracket by _______ wire or _______
-
brackets and bands in ortho are either _____ or _____to teeth
bonded or cemented
-
what type of wrought wire makes up multiple cutting edges?
(sick and) TWISTED wire
-
which are more flexible, nickel-titanium or stainless steel files?
nickel files
-
reamers have ______ twists than files
fewer
-
-
t/f hand held or rotary files/reamers are used in a root canal
true
-
what is the canal from a root canal sealed with so bacteria does not grow in its space?
gutta percha
-
what is the purpose of endodontic posts?
to retain core buildup (the big giant filling)
-
______ posts engage the root canal surface with threads like a screw
active
-
______ posts are cemented into the canal space engaging canal walls
passive
-
what post transmits less stress to the root than tapered, and forces are evenly distributed?
parallel
-
with a _____ post, a wedging force on the root has a higher risk of root fracture
tapered
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