Introduction
The acrylic resin crown is made of polymethyl methacrylate (PMMA), or today of self-curing or light-curing composites. It can look good, but resin is weak, absorbs fluids and discolours, so its main role is the temporary (interim) crown that protects a prepared tooth until the final restoration is ready.
Why temporary crowns matter
Preparing a tooth for a complete crown opens 40,000–70,000 dentin tubules, each holding an odontoblast process leading to the pulp. Left uncovered, the pulp can become irritated, infected and lose its vitality. A good temporary crown meets three groups of requirements:
How temporaries are made
Every method uses two forms: an external surface form (ESF), such as a silicone key taken before preparation, a vacuum- or pressure-formed foil, or a ready-made shell (polycarbonate for front teeth, aluminium or nickel-chromium for back teeth), and the internal tissue form (ITF), the prepared tooth or its cast. Resin is pressed or syringed between them.
Materials: PMMA, polyethyl methacrylate, microfilled composites and light-curing composites. None is best in every case: choose a stronger material for a temporary bridge, a low-shrinkage one for the direct method.