Casting alloys and implants (Ch 11 and 12) Flashcards
1
Q
what is an alloy
A
- combination of metals
- made using the ‘lost wax technique’
- gold alloys = not pure gold
2
Q
what does the ADA classify dental casting alloys based on (3 categories)
A
- high noble
- noble
- base metals
3
Q
what is the purpose of a gold alloy
A
- by combining gold with other metals to form an alloy, it creates the characteristics and hardness required as an excellent choice for an indirect restoration
4
Q
what is palladium
A
- gold alloy
- good corrosive resistance
- increases hardness of the alloy
- was less expensive but currently is more expensive than gold
5
Q
what is platinum
A
- gold alloy
- expensive
- high melting point
- difficulty mixing with gold
6
Q
what is high noble
A
- 60% noble elements
- 40% must be gold
- 20% palladium and platinum
- base metals make up the remaining 40%
- does not tarnish or corrode
- usage declining because of high cost of gold
7
Q
what is noble
A
- 25% noble elements, no requirement for gold
- 75% consists of base metals
8
Q
what are base metals
A
- less than 25% noble elements
- primary base metals used for cast alloys
- copper
- silver
- nickel
- zinc
- tin
9
Q
what is the biocompatibility of noble metals
A
- more biocompatible because they corrode less than base metals
10
Q
what can cause allergic reactions in base metals
A
- contain nickel and beryllium
- nickel has an incidence of 9-12% allergy in population
- greater incidence in women, thought to be due to nickel in jewelry
11
Q
what are wrought metal alloys
A
- an alloy that has been mechanically changed into another form to improve its properties
12
Q
what are wires
A
- wrought metal alloys
- clasps on prosthetic appliances
- lingual arch wires
- ligature wires for ortho and oral surgery for jaw fractures
- preformed provisional crowns: mostly for pedo to maintain tooth till it exfoliates, not used widely in adults
- endodontic files: twisted wire to produce cutting edges to clean and shape canals
- composed of base metals
13
Q
what are arch wires made of
A
- stainless steel
- cobalt-chrome-nickel
- titanium
- or an alloy of nickel and titanium called nitinol
14
Q
what do wires do
A
- resist deformity
- resistance creates ‘memory’
- wire tries to return to its original shape
- is it the ‘memory’ that exerts the forces that move the teeth
15
Q
what is the gauge of the wire
A
- diameter of the wire
- gauge is numbered by thickness
- thicker the wire = smaller the number
- thinner wire has more memory