A dental dam apparatus is provided for use with an associated dental molding system including an impression tray and a pour dam. The dental dam includes a substantially planar body member, and an attachment portion on the front edge of the body member. The body member defines a generally “U” shaped front edge and a generally straight rear edge extending between ends of the “U” shaped front edge. The attachment portion is configured to selectively engage a generally “U” shaped inner surface of the impression tray and to attach the body member with the tray. In that way, dental molding material poured into the dental molding system with the pour dam surrounding the impression tray and with the body member attached with the impression tray is blocked by the body member from entering into a portion of an area defined by the “U” shaped inner surface of the impression tray.