Which component ACTIVATES the polymerisation reaction in a chemically cured (autopolymerising) acrylic denture base resin?

Correct answer: C. A tertiary amine in the liquid

• A. HEAT is the activator in a HEAT-CURED resin, where the water bath decomposes the benzoyl peroxide. That is a different material from the self-cured resin described.
• B. CAMPHORQUINONE with blue light is the photoinitiator system of LIGHT-CURED resins and composites, not of chemically cured acrylic.
• C. CORRECT. In a SELF-CURED acrylic the ACTIVATOR is a TERTIARY AMINE — typically dimethyl-para-toluidine — supplied in the liquid monomer. On mixing, the amine chemically decomposes the benzoyl peroxide initiator at room temperature, liberating free radicals that begin the addition polymerisation of methyl methacrylate. The tertiary amine is also responsible for the poorer colour stability of self-cured resins, since residual amine oxidises and yellows over time.
• D. BENZOYL PEROXIDE is the INITIATOR, not the activator. It is the source of the free radicals but requires something — heat, a tertiary amine, or light — to break it down.

Note: Keep the three activation routes straight for the same benzoyl peroxide initiator: HEAT-cure (water bath), CHEMICAL/self-cure (tertiary amine), LIGHT-cure (camphorquinone plus an amine, 468 nm). Self-cured resin retains the most residual monomer, which explains both its greater porosity and its higher potential for mucosal irritation.