Avoidance of cast breakage during removal from the impression.
Breakage of a dental cast during its removal from the impression may result in inaccuracies in the finished appliance. The origin and prevention of the factors that can lead to cast breakage are found in the diagnostic phase. Casts of isolated teeth that are long, have marked gingival recession, and have a narrow clinical neck are prone to fracture. If casts of these types of teeth cannot be avoided, measures can be taken to prevent fracture. Wax can be used to thicken teeth with narrow clinical necks or to block out interproximal spaces in adjacent teeth without proximal contacts. The materials used to make the impressions and casts should also be chosen carefully. Methods of removing the cast to avoid fracture include the use of a soldering iron to cut the tray. Once the tray is sectioned, the impression material is free to elongate, and the cast can be removed easily.