Lab area: casting bench / flexible injection area
Version: v1.0
Last reviewed: 16/02/2026
Next review: 16/08/2026
What this is for:
To safely and consistently repair flexible Valplast dentures — either joining acrylic to Valplast or repairing Valplast to Valplast — with correct casting protocol and minimal remake risk.
You need
Materials
- Valplast resin – [confirm: exact product name + shade system]
- Repair acrylic – [confirm: brand + type]
- Stone / investment – [confirm: product name]
- Separating medium – [confirm: product]
- Aluminium oxide for sandblasting – [confirm: micron size]
- Mechanical retention beads or burs (if required)
Equipment
- Valplast injection unit – [confirm: model]
- Approved Valplast flask system – [confirm: type]
- Pressure pot – [confirm: pressure setting]
- Sandblaster
- Steam cleaner
- Trimmer + polishing lathe
- Thermometer – [confirm: required temp]
PPE
- Safety glasses
- Mask/respirator (dust + fumes)
- Heat-resistant gloves
- Lab coat
- Closed shoes
Before you start (setup)
- Confirm case prescription and repair type (acrylic → Valplast or Valplast → Valplast).
- Check denture is clean and disinfected.
- Inspect for fractures, distortion, missing clasps.
- Confirm shade match and material batch.
- Check injection unit is serviced and at correct temperature: [confirm: cylinder temp °C].
- Confirm casting time window once heated: [confirm: max hold time].
Steps
- Clean the denture with steam and dry fully.
- Roughen the repair area using coarse bur or sandblast.
- Create mechanical retention undercuts (Valplast will not chemically bond to acrylic).
- Remove any sharp acrylic edges and bevel margins.
- Block out unwanted undercuts with wax.
- Invest the case in approved Valplast flask system.
- Allow stone/investment to fully set: [confirm: setting time].
- Place flask in heating unit and preheat to [confirm: preheat temp °C].
- Heat Valplast cartridge to [confirm: injection temp °C] for [confirm: heating time].
- Inject Valplast under pressure [confirm: pressure setting].
- Maintain pressure for [confirm: hold time].
- Allow controlled cooling to room temperature before deflasking (do not quench unless manufacturer specifies).
- Deflask carefully and trim excess.
- Finish and polish using approved Valplast polishing protocol (no pumice contamination).
Quality checkpoints (what “good” looks like)
- Repair area fully fused with no visible gap.
- No porosity or bubbles.
- No movement between acrylic and Valplast section.
- Clasps return to original flexibility.
- Surface smooth, not chalky or burnt.
- Shade consistent with original.
- Fit unchanged on master model (if available).
If gap or separation is visible → stop and assess retention design before polishing.
If porosity present → check injection pressure and heating time immediately.
Common mistakes + fixes
Gap at join → insufficient mechanical retention → deepen undercuts and reinvest.
Bubbles in repair → low pressure or short heat time → confirm injection settings.
Burnt surface → overheating cartridge → confirm temp calibration.
Weak repair → contaminated surface → steam clean + sandblast before reinvesting.
Distortion → deflasked too hot → allow full cooling before opening.
Shiny but rough feel → wrong polishing compound → use Valplast-approved polish only.
Clean-down + reset
- Remove all stone and debris from flask system.
- Empty and clean injection chamber.
- Log cartridge batch used.
- Wipe down bench and sandblaster area.
- Return burs and tools to correct drawers.
- Leave injection unit at standby setting [confirm: standby temp].
Escalation
Technical issue → Carly → Golboo → Garth
Clinical judgement (fit/function concern) → senior prosthetist → Garth
Workflow/system issue → Eloise or Golboo → Georgie
Record keeping
Log in:
- Ticketing system – repair type + batch number
- Material batch log – Valplast cartridge ID
- Injection settings used
- Any deviation from standard protocol
- Rework reason (if applicable)
Footer:
Version 1. Date 16/02/2026. If you change a setting, update this poster and log the change.
