Dental Dental Materials Materials

Lesson 8Lesson 8

Golds and other MetalsGolds and other Metals

1. 1. Gold FoilGold Foil• Gold and Silver are Precious metals.• Gold foil is pure gold- 24 Karat,

comes in small pieces, is SOFT• DIRECT restoration, the small pieces

are heated (annealed), placed in prep, condensed (malleable), carved.

• Disadv- time to place, soft, cost• Adv- no tarnish

2. Types of 2. Types of Casting AlloysCasting AlloysIndirect RestorationsIndirect Restorations

• Type I- soft no occlusion

• Type II- inlays• Type III- hard,

crown & abut• Type IV- partial

denture framework

• Most gold is an alloy

• Noble- Gold Au palladium Pd platinum Pt• Base- all other

• $$$, ins codes

High noble, Noble, BaseHigh noble, Noble, Base• High Noble- gold 40% or more, total

of Au, Pd & Pt =60% or more• Noble- total of Au, Pd & Pt = 25%

minimum• Base- less than 25% Au, Pd % Pt,

may contain 0% noble metals

3&6. Shape alloy- 3&6. Shape alloy- CASTingCASTing• Die, articulated• Wax pattern• Sprue in ring• Invest• Burn out• Cast • Finish• Seat

CastingCasting

4. Join metals4. Join metals• If not cast in 1 piece- Weld or Solder• Weld- melts part of the objects being

joined and fuses them together, sometimes with additional filler material

• Solder- joins 2 metals by using a joint made of a 3rd material that melts at a lower temp

Dental SolderDental Solder

5. Troy Weight system5. Troy Weight system• Troy weight originates from the city

of Troyes in France, an important trading city in the Middle Ages. Troy weight is used for precious metals and gems. A pennyweight (dwt) is the main unit and there are 20 pennyweight in an ounce. In Troy there are only 12 ounces in a pound- not 16.

7. Metals in PFM7. Metals in PFM• Porcelain= Ceramic- claylike material

with a glaze

• Palladium alloys • Nickel-chromium alloys• Cobalt- chromium alloys

8. Partial Denture 8. Partial Denture FrameworksFrameworks

Nickle- chromium alloys

VocabVocab• Wrought gold alloy- bend at room

temp, partial denture clasps