Custom impression trays. Part II: Removal forces.

When choosing a material for making custom impression trays, it is important to understand the forces to which the tray will be subjected during removal of the completed impression from the oral cavity. Such forces have not been recorded in the dental literature. The purpose of Part II of this three-part series was to record these forces in vitro, using two different tray-removal methods. A polymethyl methacrylate custom tray was used during this study. Results from this investigation indicated that it is easier to remove a completed impression, made with a custom tray, by a single point of anterior force application (224 N) than by force application evenly around the tray (514 N). The recorded force values from this investigation will be used in Part III of this series.