10 Plastic Trays Used to Hold Plaster Models of Teeth, Specially Designed Plaster-Cutting Saw Blades for Dental Use, Plastic Rings and Their Bases Used to Enclose the Molds Used in Dental Casting, Plastic Sprues and Plastic Crucible Formers Also Used in Dental Casting, and Plastic Trays Used to Hold Plaster in which the Dentist Records the Occlusal Surfaces of His Patient's Teeth