ch 10 dental mat cont
Card Set Information
ch 10 dental mat cont
dental mat cont
dental mat ch 10 cont
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?
which are more desirable in crystal formation, small or large grains?
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
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?
porcelain ______ fuses to the oxide layer
t/f there is a slight change in metal composition to withstand high heat of firing porcelain (turning into glass)
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
what must the coping of a pfm be besides at least .3mm thick to prevent distortion at high temps?
NO SHARP ANGLES
what does the thickness of the porcelain need to be in order to obtain a solid structure for a crown?
what are the three types of porcelain alloys?
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
what are the most common base metal alloys for removable prosthetic casting alloys? (2)
(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
t/f noble metals are more biocompatible with oral tissues
____ metals corrode less than base metals
which corrosion products are responsible for allergic responses?
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
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
close holes in the occlusal surface from grinding
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
What kind of solder is used for orthodontics-fixed space maintainer components, solder wire components together
Pediatric Dentistry-space maintainer?
Wrought alloy metals are formed _____ the metal is cast
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
what kind of wire is used for clasps of a removable prosthesis?
which wire is used for ortho arch wires?
_______ wires in ortho or oral surgery are made out of wrought metal
endodontic files and reamers are made out of what type of wire?
what is it in an arch wire that exerts the forces that move the teeth?
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?
reamers have ______ twists than files
reamers cut _____
t/f hand held or rotary files/reamers are used in a root canal
what is the canal from a root canal sealed with so bacteria does not grow in its space?
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
______ posts are cemented into the canal space engaging canal walls
what post transmits less stress to the root than tapered, and forces are evenly distributed?
with a _____ post, a wedging force on the root has a higher risk of root fracture