3. Composition and preparation of heat-cured acrylic
Covers the composition of heat-cured acrylic denture base resin, set out in a table of liquid and powder components with their roles, including the monomer, cross-linker, inhibitor, polymer pearls, initiator, plasticizer and opacifiers, plus storage advice. It then walks through preparation step by step, from waxing out and insulating the mould to mixing, waiting for the dough stage, packing, curing and finishing. A water-bath curing schedule with temperatures and times is given, followed by a table of common faults and their causes such as gas pores, moisture pores and cracking.
Topic 3 of 52 in the MU Sofia syllabus for Dental Materials (Dental Medicine, Year 1). The free AceMed note covers it in 5 sections, about 262 words (3 min of reading), with 16 flashcards.
In this note
Introduction
Composition
Preparation
Curing schedule
Faults to avoid
Introduction
Heat-cured acrylic is the standard material for denture bases. Heat activates the initiator, and the denture is made by the lost wax technique in a two-part metal flask, called a cuvette.
Composition
Keep the liquid in a cool, dark place, in a UV-proof bottle that is not quite full, because oxygen in the air also inhibits polymerization. Keep the powder in a tightly closed container.
Preparation
Wax out: model the denture in wax, invest it in plaster in the flask, open the flask and remove the wax with hot water.
Insulate: coat the plaster with an alginate solution or calcium chloride with water glass, so that moisture stays out of the resin.
Mix: combine powder and liquid in a clean vessel, usually 3:1 by volume, and cover it.
Wait: leave it for 5 to 20 minutes, depending on room temperature. The pearls swell as monomer enters them.
Pack: at the dough stage, place the resin in the mold with a slight excess and press it. Clamp the flask to keep up the pressure.
Cure: follow the water-bath schedule, then cool slowly.
Finish: break away the plaster, then clean, grind and polish.
The dough can only be packed in that stage, which lasts at least 5 minutes. Keeping the powder and liquid in a refrigerator extends it.
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