Section 872.3660 - Impression material(a)Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be placed on a preformed impression tray and used to reproduce the structure of a patient's teeth and gums. The device is intended to provide models for study and for production of restorative prosthetic devices, such as gold inlays and dentures.(b)Classification. Class II (Special Controls).52 FR 30097, Aug. 12, 1987, as amended at 68 FR 19738 , Apr. 22, 2003