Ultramicrotome for Hard Tissue

Abstract

An ultramicrotome was designed specifically for cutting hard materials such as tooth enamel. Thermal and mechanical stability were achieved by utilizing a special marble base. At near room temperature, the coefficient of thermal expansion measured parallel to the quarry bed is negligible. A massive block of this marble, properly oriented, is used as a one-piece base. An Invar thermal expansion rod, rigidly anchored to the base, extends through a 7. 5 cm hole to the front of the block. A unique positive drive moves the specimen past the knife and ensures that its lateral position during cutting is precisely reproducible and independent of wear or play in the drive mechanism. This instrument is now in routine use to prepare ultrathin sections of fully matured adult human dental enamel. Electron micrographs of such sections are presented. Ultrathin sections were also cut successfully of soft biological tissue.