PMMA Glass Transition Temperature — NDEB AFK MCQ
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Correct answer: E — 105°C
The glass transition temperature (Tg) of PMMA (polymethyl methacrylate, denture base acrylic) is approximately 105°C. Below Tg, the material is rigid and glass-like; above Tg, it becomes soft and pliable. This is clinically relevant for denture relining and repair (heat is used to soften the material) and explains why hot beverages (60-70°C) do not distort dentures (well below Tg). However, prolonged exposure to boiling water can cause warpage. Denture base material must withstand the oral thermal environment without softening.
Reference: Anusavice – Phillips' Science of Dental Materials, 13th ed., 2022