In a method of obtaining a gum impression of a patients mouth and measuring jaw relations, a dental impression tray assembly including a lower tray and an upper tray to fabricate a denture, is used. The lower tray includes a first piece and a pair of second pieces and the upper tray includes a third piece and fourth piece. The method includes inserting the lower tray loaded with an impression material into the mouth to take an impression taking out the lower tray from the mouth and cutting the impression material along a borderline between the first piece and the pair of second pieces separating the first piece from the pair of second pieces attaching an intra-oral tracer to the first piece and inserting the first piece, to which the intra-oral tracer is attached, and the third piece into the mouth to measure the jaw relations.
