Gasket for vacuum thermoforming machine

摘要

A gasket for vacuum thermoforming machines, which gasket is designed to be positioned on the perforated base plate of the thermoforming machine to cover selected ones of the vacuum openings in the base plate. An opening is provided in the center of the gasket for concentrating the vacuum in this area and increasing the vacuum applied to a heated plastic sheet or plate positioned above a dental impression cast located on the base plate in the gasket vacuum opening. The vacuum applied by the vacuum thermoforming machine is thus concentrated within the confines of the vacuum opening of the gasket to more efficiently mold the soft plastic plate over the dental impression cast and form a plastic retainer for straightening teeth. A method for molding a plastic retainer for straightening teeth, which method includes the steps of placing a gasket having a vacuum opening over the perforated base plate of a vacuum thermoforming machine such that some of the vacuum openings are covered by the gasket and others are exposed in the vacuum opening in the gasket; positioning a plastic plate above the gasket adjacent to the heater in the vacuum thermoforming machine; placing a dental impression cast on the perforated base plate in the opening in the gasket; heating the plastic plate; initiating the vacuum in the perforations in the base plate defined by the opening in the gasket; and lowering the softened plastic plate over the dental impression. Additional, and/or oversized perforations may also be provided in the gasket vacuum opening to increase the vacuum applied to the plastic plate.