Dental cast tray assembly

In one embodiment of the present invention, a dental cast tray assembly used to form a dental cast model comprises a base and a tray removably mounted on the base. The base includes a top surface, a flat bottom surface, a front wall, a rear wall and a plurality of projections formed on its top surface in a non-recurring, random pattern. Each of the plurality of projections is generally cylindrically-shaped and includes a convex free end. The tray includes a top surface adapted to support the dental cast model, a flat bottom surface, a front wall, a rear wall, a retention bar formed on its top surface and a plurality of openings formed in its bottom surface in the same non-recurring, random pattern in which the plurality of projections are disposed on the base. Each of the plurality of openings is defined by four sidewalls and is generally hourglass shaped in lateral cross-section. Two of the four sidewalls which define each of the plurality of openings include an elongated rib. In use, the tray is mounted on the base such that the bottom surface of the tray abuts against the top surface of the base and so that the front wall of the tray is flush with the front wall of the base. With the tray mounted on the base, one projection in the base projects into an associated opening in the tray, the elongated ribs serving to retain each projection within its associated opening with limited retention.