Posterior palatal seal adaptation: influence of processing technique, palate shape and immersion.

Accuracy of fit of denture bases is critical to adequate retention. This study compared the dimensional change of a newer continuous-injection technique with a standard trial-pack technique as determined by measuring the posterior palatal border opening. The influence of palate shape and immersion were also assessed. Stone casts were made from master moulds with either a high or flat palate. Denture base adaptation was measured at 5 mm intervals across the entire posterior palatal border. Measurements were made after deflasking, trimming and polishing, and after immersion in room temperature water for 1 h, 1 day and 1 week. Statistical analysis (P < 0.05) showed that where differences occurred between the two techniques, openings were always smaller for the continuous-injection technique. It was also shown that dimensional changes were always larger for the flat palate compared with the high palate. Dimensional change using the continuous-injection technique was reduced by immersion in water, while no influence was observed for the trial-pack technique. It was concluded that the continuous-injection technique showed smaller dimensional changes compared with the standard trial-pack technique, and that these changes were influenced by palate shape and immersion in water.