Explains how heat-cured acrylic denture resins are made, focusing on the water-bath temperature schedule and why heating too fast causes porosity and residual monomer. Covers mechanical values in a summary table, shrinkage figures, water uptake and solubility, ageing causes, biological effects of residual monomer and colourants, and microwave and rapid heat-curing alternatives.
Topic 38 of 52 in the MU Sofia syllabus for Dental Materials (Dental Medicine, Year 1). The free AceMed note covers it in 8 sections, about 435 words (3 min of reading), with 15 flashcards.
In this note
Introduction
Why the temperature schedule matters
Mechanical properties
Shrinkage
Water and solvents
Aging
Biological properties
Other ways of curing
Introduction
Heat-cured polymers are acrylic resins in which heat activates the initiator. Careful temperature control gives long polymer chains, little residual monomer and the best properties among basic denture resins.
Why the temperature schedule matters
About 60 °C: benzoyl peroxide decomposes at the best rate, which gives the longest chains. Higher temperatures break it down too quickly.
Heat from the reaction: chain growth is exothermic and heats the dough 20 to 30 °C above the water. If the total reaches 100.3 °C, the monomer boils and forms gas pores.
Final stage at 100 °C: after about 90 minutes the initiator runs out. The hotter water then polymerizes the unreacted monomer.
If the water is heated too fast, the resin can pass 120 °C. It becomes porous and poorly colored, with a degree of polymerization of about 1800 and over 3% residual monomer. A correct schedule gives a degree of about 2500, a molecular weight of about 250,000 and 0.3 to 0.5% residual monomer.
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