Dental Materials Dental Materials Lesson 8 Golds and other Metals

1. Gold 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 Casting Alloys Indirect 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, 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- CASTing Die, articulated Wax pattern Sprue in ring Invest Burn out Cast Finish Seat

Casting

4. 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 3 rd material that melts at a lower temp

Dental Solder

5. 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 PFM Porcelain= Ceramic- claylike material with a glaze Palladium alloys Nickel-chromium alloys Cobalt- chromium alloys

8. Partial Denture Frameworks Nickle- chromium alloys

Vocab Wrought gold alloy- bend at room temp, partial denture clasps