FDA Cleared, last investigation 02-08-2024

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.