Digital Fabrication of FPDs UPDATED ACTUAL Questions
and CORRECT Answers
Why do we create a die spacer? Creates space for cement --> without it the crowns won't fully seat
When doing the wax pattern: when do we cut back? We cut back when we are doing a PFM crown
How much do we cut back? - We want to cut back so there is 1.5 - 2.0mm of clearance
What if we cut back more or less? - >2mm = fracture
- <1.5mm = crown can't fit all esthetic shades
What is Spruing? What does it help with? Attach a channel to a wax pattern to allow a path for molten metal to flow into the
mold eventually
What is investing used for? We surround the wax-up with investing materials so that we can melt the wax and
have a void
What is the investing material for gold alloys? Gypsum
What is the investing material for base metal alloys for Phosphate
FPD?
What is the investing material for base metal alloys for Silica
RPD?
What is the highest melting temp for investing materials? Hottest melting temp = Silica = RPD
Gypsum, Silica, Phosphate Phosphate = FPD
Match them to FPD, RPD, and Gold alloy creation Lowest melting temp = Gypsum = Gold alloy
When the metal is in the investing material: how do we 1. Metal flows into absent wax mold (wax has been burned out)
make sure the framework forms? 2. Heat-press the metal in vacuum
3. Centrifuge it
Do we mill or 3D print crowns? Mill
What are the indications for 3d printing crowns? Great for temp crowns
What is the purpose of Crystaliztion / Sintering? Gives crown the final mechanical properties
How long does it take? Takes between 12 min and 10 hours
What technique is more aesthetic: traditional or digital? Traditional (if you have a good lab tech)
What is the fabrication method for Cast Metal (Gold)? Wax Pattern OR Casting
What is the workflow type? Conventional workflow
What is the fabrication method for PFM? Wax Pattern + Casting of Metal + Porcelain Layering last
What is the workflow type? Conventional Workflow
and CORRECT Answers
Why do we create a die spacer? Creates space for cement --> without it the crowns won't fully seat
When doing the wax pattern: when do we cut back? We cut back when we are doing a PFM crown
How much do we cut back? - We want to cut back so there is 1.5 - 2.0mm of clearance
What if we cut back more or less? - >2mm = fracture
- <1.5mm = crown can't fit all esthetic shades
What is Spruing? What does it help with? Attach a channel to a wax pattern to allow a path for molten metal to flow into the
mold eventually
What is investing used for? We surround the wax-up with investing materials so that we can melt the wax and
have a void
What is the investing material for gold alloys? Gypsum
What is the investing material for base metal alloys for Phosphate
FPD?
What is the investing material for base metal alloys for Silica
RPD?
What is the highest melting temp for investing materials? Hottest melting temp = Silica = RPD
Gypsum, Silica, Phosphate Phosphate = FPD
Match them to FPD, RPD, and Gold alloy creation Lowest melting temp = Gypsum = Gold alloy
When the metal is in the investing material: how do we 1. Metal flows into absent wax mold (wax has been burned out)
make sure the framework forms? 2. Heat-press the metal in vacuum
3. Centrifuge it
Do we mill or 3D print crowns? Mill
What are the indications for 3d printing crowns? Great for temp crowns
What is the purpose of Crystaliztion / Sintering? Gives crown the final mechanical properties
How long does it take? Takes between 12 min and 10 hours
What technique is more aesthetic: traditional or digital? Traditional (if you have a good lab tech)
What is the fabrication method for Cast Metal (Gold)? Wax Pattern OR Casting
What is the workflow type? Conventional workflow
What is the fabrication method for PFM? Wax Pattern + Casting of Metal + Porcelain Layering last
What is the workflow type? Conventional Workflow
