Multilayer PMMA Disc

· The shoulder shall not be prepared in the area of corner and sharp edge. The shoulder shall be prepared in the shape of a round inner edge or inclined surface.

· The space of 1mm is required to be reserved for the preparation of the cutting edge, so as to ensure that the PMMA block can achieve the ideal grinding effect in the process of CAD / CAM. The preparation of the cutting edge should be at the enamel layer, and avoid the preparation at the point or area of stress concentration.