week 4: Gold Alloys

Question 1

Why are metals electrically conductive

Answer 1

The e- don’t bond to a specific atom, but float freely around in the metal

Question 2

What is a dislocation

Answer 2

a defect in the attic structure in which few ions in a layer are missing

Question 3

what characteristics about grains control the mechanical properties of a metal

Answer 3

Grain size and shape

Question 4

How does Grain boundaries impact the slipping or dislocation of a crystal lattice

Answer 4

They stop the progression of dislocations

Question 5

Describe the impact of a high concentration of grain boundaries will have on the metals physical properties

Answer 5

increase the hardness
increase the yield strength
increase stiffness
increase brittleness (less Ductile)

Question 6

How will heat and rapid cooling impact the grain boundaries produced in metals

Answer 6

Heat will increase the size, but decrease the number of grain boundaries

Rapid cooling will increase the # but decrease the size of boundaries.

Question 7

Provide an example of a noble and base metal

Answer 7

Noble: gold, palladium, platinum
Base: titanium, nickle, copper, silver, zinc

Question 8

What are the advantages and disadvantages of pure gold

Answer 8

Advantages
- Corrosion resistant
- No cement needed

Disadvantages
- Low rigidity and elastic limit
- High cost

Question 9

Indications for pure gold

Answer 9

Class 1 Restoration in (low) occlusal load
Sandwich gold-titanium foils are used for class 2 restorations

Question 10

What are the 6 Alloy metals/ combinations that are added with gold

Answer 10

1. Copper/silver
2. zinc
3. iron
4. indium
5. Nickel and cobalt

Question 11

What are the benefits/reasons they are alloyed with gold (everyone take one)

Answer 11

Copper/silver: Hardens and strengthens noble metals

Zinc: low melting point so hardness gold base and prevents oxidation during casting

iron: enhances bonding between ceramic and gold alloys

Indium: encourages small grains

Nickle & Cobalt: used in low cast alloys

Question 12

what is the minimum gold percentage needed for an alloy.

Answer 12

75%

Question 13

What is the risks associated, if any, with the previous alloy metals

Answer 13

Nickle can cause allergic reactions

Question 14

What are Type 1 Gold Castings used for

Answer 14

Inlays
low stress bearing rests with lots of supportive tooth structure.

Question 15

What are Type 2 Gold Castings used for

Answer 15

Inlays or inlays
moderate stress bearing restos
Most common inlay gold material

Question 16

What are Type 3 Gold Castings used for

Answer 16

Inlays, poetics, crown, saddles
high stress bearing restos

Question 17

What are Type 4 Gold Castings used for

Answer 17

saddle, crown, bridge, clasps
very high stress bearing restos
partial denture framework

Question 18

Describe palladium

Answer 18

excellent corrosion resistance,
Higher melting point than gold
harder then gold

Question 19

Describe platinum

Answer 19

higher melting point then palladium
poor mixing capability with gold
high cost

Question 20

what are the 5 important properties of casting metals

Answer 20

Solidus(setting temp)
Liquidus(melting temp)
density
yield strength
hardness

Question 21

Describe Solidus, liquids, density and yield strength

Answer 21

solidus: important in soldering metal elements and porcelain+metals

liquidus: important in casting procedure

Density: Amount of mass in volume G/mm3
- higher the density the better casting
- noble metals >base metals

yield strengthmaximum stress applied with no plastic deformation
- Base metals>noble metals

Hardness: 125-380 kg/mm3
-enamel = 343kg/mm3

Question 22

what is the highest corrosive alloy combination and its allergy rates

Answer 22

nickle+beryllium
8-15%

Question 23

what are wrought alloys and give an example used in dentistry

Answer 23

mechanically shaped after the metal is made into a block (endo files, orthodoxy wires, prosto wires)

Question 24

Describe the reaction involved with ceramic and metal bonding

Answer 24

Cemical reaction that occurs due to formation of an oxide layer

Question 25

what metals provide the oxide layer

Answer 25

tin, iron, gallium, indium

Question 26

the solidus temple should be _______ then the fusion temp of a ceramic. The ______ should be compatible with the ceramic and metal

Answer 26

higher, Coefficient of thermal expansion

Question 27

describe a flux

Answer 27

cleans and removes the oxide layer from the surface of an alloy

Question 28

describe a solder

Answer 28

group of alloy used to weld metals together

Question 29

what flux is used for gold base alloy and for a base metal alloy

Answer 29

Gold base= borax
base metal= potassium fluoride

Question 30

Physical diagnosis relies on info from…

Answer 30

Info from inspection, palpation, percussion, auscultation = diagnosis

Question 31

What are some classic expectations of edentulous patients?

Answer 31

restoring speech, rid of wrinkles, eating

Question 32

List the factors you need to consider when diagnosing and treatment planning for edentulous patients. Give examples and the implications of those examples

Answer 32

M muscosa:
erosive lichen planus, ulceration -> dentures cause to much discomfort to be worn
M mouth:
limiting access ie. arthritis of TMJ, submucous fibrosis and scleroderma-> hard to put in imp. trays, just replicate pre-exisitng set
B bone metabolism:
ex. fibrosis, dysplasia, acromegaly -> changes in jaw makes dentures loose fit quickly
N neuromuscular:
ex. parkinsons, epilepsy, dyskinesia -> accurate jaw relations and denture security is an issue (+ make radio-opaque dentures incase of swallowing)
S salivary dys:
ex. sjogrens disease, radiotherapy -> without saliva get generalised soreness from dentures
I immunological:
ex. allergy -> problems during imp. and PMMA residual monomer, nickle in metal base
D dentures:
ex. cerebral atheroma, stroke -> good control of MOM and facial muscles leads to good denture function therefore defective means dentures act as large forgein body in the mouth

Question 33

What is combination syndrome

Answer 33

Mx = edentulous
Md = 6 anterior teeth only (free end saddles)
Pressure of teeth against denture in anterior region = bone loss/flabby ridge in mx

Question 34

What occurs with
- too little
- irregular
- excessive
- normal
alveolar resorbtion

Answer 34