Partial Denture Alloys

Question 1

what are the alloy hardening processes?

Answer 1

work, solution, order, precipitation

Question 2

what are the alloy annealing processes?

Answer 2

homogenisation, stress relief

Question 3

what are the ideal properties for partial denture alloys?

Answer 3

rigid, strong, hard, ductile, precise casting, melting point, density

Question 4

what are the different types of partial denture alloys?

Answer 4

ADA type 4 gold, CoCr, white gold, titanium

Question 5

what does the youngs modulus and elastic limit need to be for the base of a denture?

Answer 5

high YM to maintain shape in use and high EL to avoid plastic deformation

Question 6

what does the youngs modulus and elastic limit need to be for the clasp of a denture?

Answer 6

low YM to allow flexure over tooth and high EL to maintain elasticity over the wide range of movement

Question 7

what are the uses for pure gold?

Answer 7

class 3 and 4 cavities

Question 8

what are the effects of copper in an alloy?

Answer 8

solid solution in all proportions, solution hardening, order hardening, reduced melting point, little/no coring, imparts red colour, reduces density, base metal

Question 9

what are the effects of adding silver to an alloy?

Answer 9

solid solution in all proportions, solution hardening, precipitation hardening with copper and heat treatment, can allow tarnishing, molten silver absorbs gas, whitens alloy

Question 10

what are the effects of adding platinum to an alloy?

Answer 10

solid solution with gold, solution hardening, fine grain structure, coring can occur

Question 11

what are the effects of adding palladium to an alloy?

Answer 11

less coring than platinum, coarser grains than platinum, absorbs gas when molten (porous casting)

Question 12

what does zinc do in an alloy?

Answer 12

it is a scavenger

Question 13

what does nickel do in an alloy?

Answer 13

increases hardness and strength

Question 14

what does indium do in an alloy?

Answer 14

fine grain structure

Question 15

what heat treatments are used for type 4 gold alloys?

Answer 15

quench after casting, homogenising anneal, if cold worked then stress relief anneal, heat harden

Question 16

what would type 4 gold alloy be used for on a denture?

Answer 16

clasp

Question 17

what is CoCr used for?

Answer 17

wires, surgical implants, cast partial dentures, connectors

Question 18

what does cobalt do in CoCr?

Answer 18

forms solid solution with Cr, increased strength, hardness, rigidity, coring possible

Question 19

what does chromium do in CoCr?

Answer 19

forms solid solution with Co, increased strength, hardness, rigidity, coring possible, forms passive layer

Question 20

what are the effects of nickel in CoCr?

Answer 20

replaces some Co, improves ductility, slight reduction in strength, sensitivity

Question 21

what techniques are used for CoCr finishing?

Answer 21

soundblast, electroplate, abrasive wheel, polishing buff

Question 22

what is the hardness of CoCr compared to gold?

Answer 22

it is harder so you can wear it in the mouth better although finishing and polishing time is consuming

Question 23

what is the ductility of CoCr?

Answer 23

low

Question 24

what are the uses of titanium?

Answer 24

implants, crown and bridge, maxillo-facial skull plates, partial dentures

Question 25

what are the advantages of titanium?

Answer 25

good biocompatibility, good corrosion resistance

Question 26

what type of casting is needed for CoCr?

Answer 26

precision casting