SM20 - 20% Au, Noble Crown and Bridge Alloy, Type IV
SM20 is an economic golden crown and bridge alloy from Strategy Milling. It is suitable for full-cast crowns and bridges, inlays, and onlays.
Advantages
- Affordable, yellow crown and bridge alloy
- Rich yellow color
- Economical due to low density
- Brilliant high gloss achieved with ease by polishing
Indications
- Onlays
- 3/4 crowns
- Crowns
- Telescope and conus crowns
- Root canal post and cores
- Short- and long-span bridges
- Inlays and onlays
Composition
Ag 40.75
Au 20.0
Pd 14.0
In 11.0
Cu 10.75
Sn 2.0
Zn 0.5, Pd 1.0, Ru 1.0
Technical data
| Type | Noble |
| Color | Yellow |
| Density (g/cm³) | 10.8 |
| Melting range (°C) | 750 - 840 C |
| Casting temperature (°C) | 960 - 1020 C |
| Modulus of Elasticity (MPa) | 90 |
| Elongation (%) - As cast | 5 |
| Vickers hardness - As cast | 195 |
| 0.2% proof stress (MPa) - As cast | 195 |
| Tensile Strength (MPa) - As cast | 570 |
Polishing Recommendations
This is a Type IV alloy which is hard.
Begin with a Dedeco White Flexie Classic Knife-Edge Abrasive Wheel.
Follow with a new or newer Robinson Soft Bristle Brush using medium pressure and Fabulustre Polishing Compound, the type for final buffing of Au, Ag, Pt, Al, Ni, Fe, and Cu, (two tone gold colored label).
Short, worn bristle brushes are not great, in my opinion. Follow that up with a soft felt wheel, light on pressure and light on polish.
This combination works very well at leaving a smooth, high shine.