A cassette for dental instruments includes two substantially identical trays with each tray having a hinge to permit removable assembly of the tray to the other tray to form the cassette or enclosure. Each tray has apertures or holes wherethrough liquid cleansing agents can be sprayed into and can be drained out of the tray. Ribs are removably mounted into the trays and are held in spaced substantially parallel positions therein. At least one of the ribs has a clamping device for holding dental instruments in positions substantially transverse to the ribs. An intermediate locking plate is removably mounted into each tray above the ribs to further secure the dental instruments in their clamped positions in the tray. The two trays when assembled together as a cassette are readily washed, autoclaved, stored and transported together, while each tray can contain a separate set of dental instruments.