Custom impression trays with a new hypoallergenic material

Abstract

A custom tray is essential for the accurate reproduction of oral tissues.l The limitations of stock trays are well documented; they can rarely be used for final impressi0ns.l The earliest custom tray materials, now obsolete, were cast low-fusing alloys and swaged stainless steel. Shellac, commonly reinforced with metal particles, is a cheap alternative still in use, but most modern custom trays are polymeric. The sprinkle-on procedure that uses autopolymerizing acrylic resin powder and liquid has been used for many years, but it has largely been superseded by the application of a hand-formed sheet of acrylic resin dough adapted to the cast, which polymerizes in situ and is then trimmed as required. Vacuumand pressure-formed trays with thermoplastic sheets are popular materials. In recent years visible light-cured materials have become widely used. A new custom tray material (Hydroplastic, De Plas-Dent Co., Ltd., Smethwick, Warley, U.K.), has been produced. This is a polycaprolactone, plasticizer free, which is polymerized by heat, which opens the lactone ring. The material is manufactured in the form of soft-colored plastic beads (Fig. l), which soften in hot water and are molded to produce a translucent pliable putty-like mass, which is adapted to a cast to form a custom tray. This material has a lower modulus of elasticity than other custom tray materials, but it recovers completely after deformation.2 Until further research on its properties is done, its use should be limited to edentulous patients. The procedure for its use is relatively simple.