Coating and flasking

Understanding Dental Flasking and Coating

• Flask Types and Selection — Dental flasks come in upper and lower halves that hold the investment plaster during the boil-out and packing sequence. Aluminium flasks are lightweight and conduct heat evenly; brass flasks are more durable for high-volume labs.
• Investment Plaster for Flasking — Type III dental plaster or low-expansion stone is used to invest the wax denture in the flask. Over-expansion of the investment causes dimensional changes in the final denture -- use the correct powder-to-water ratio precisely.
• Separating Media (Coating) — Separating agents prevent plaster from bonding to acrylic resin during processing. Sodium alginate (cold mould seal) is the standard separating agent; apply 2 coats to the stone surface after boil-out and allow each coat to dry.
• Boil-Out Procedure — Boiling the closed flask in water melts the wax pattern out of the investment, leaving a clean mould cavity. Use boiling water for a minimum of 5 minutes; rinse the mould cavity with boiling water to remove all wax residue before applying separating agent.
• Acrylic Packing — Heat-cure or cold-cure acrylic resin is mixed to a dough stage and packed into the mould cavity. Pack in trial closure stages, releasing excess material, to prevent porosity and ensure complete mould fill before final closure.
• Processing and Curing — Heat-cure acrylic is processed in a water bath at 74 deg C for 8 hours or 100 deg C for 30 minutes. Slow processing at 74 deg C minimises porosity from monomer boiling; rapid processing requires careful temperature control.

Denture Processing Materials at a Glance

How to Flask a Complete Denture

1. Invest the wax trial denture in Type III plaster in the lower flask half and allow to set.
2. Close the flask with plaster in the upper half, ensuring teeth are embedded without plaster on their labial surfaces.
3. Boil the closed flask to melt and remove the wax pattern -- rinse the cavity with boiling water.
4. Apply two coats of separating agent (sodium alginate) to all plaster surfaces and allow to dry.
5. Mix heat-cure acrylic to dough stage, pack the mould, process at 74 deg C for 8 hours.

Availability & Delivery in Egypt

MedSTA supplies dental flasking kits, separating agents and processing materials to Egyptian dental laboratories with EGP pricing and nationwide delivery. Materials are compatible with standard Egyptian lab workflows.