The validity of maxillomandibular records made with trial and processed acrylic resin bases

A comparison was made of the accuracy of maxillomandibular records made with trial bases fabricated on casts with blocked-out undercuts and those made with final processed bases. The results of the study indicate that significantly greater occlusal discrepancies occurred after the final processing when trial bases were used to obtain jaw records. With processed final bases, the denture superstructures are attached to the same bases used for recording, transferring, and adjusting the occlusion of the dentures. Thus, the dimensional changes of processing and the uneven setting of the bases upon the unevenly resilient mucosa are incorporated into both records and dentures. When placed in the mouth the conditions during and after fabrication are similar and occlusal discrepancies are minimal. With the trial base technique, the imperfections of both bases and clinical records are transferred to the final denture bases, which also have processing inaccuracies and which settle differently when placed upon the resilient tissue support. The divergent conditions created by the use of two types of bases are reflected in occlusal discrepancies of the completed dentures.