LINEAR DIMENSIONAL CHANGE OF HEAT-CURED ACRYLIC RESIN COMPLETE DENTURES AFTER RELINE AND REBASE

Statement of problem. Relining and rebasing of complete dentures are c ommon procedures to improve the fit of the prostheses. After relining or rebasing, adjustments may be required because of dimensional change that occurs during reprocessing of the denture when new denture base material is polymerized. Purpose. This study analyzed the linear dimen sional change of heat-cured acrylic resin that occurs during reline an d rebase procedures for complete dentures. Material and methods. Twent y-two maxillary and mandibular complete denture bases with artificial teeth were saturated by immersion in distilled water at 37 degrees C /- 1 degrees C. Fine crosses were marked on the incisal edges of the c entral incisors and the supporting cusps of the second molar teeth. Di stances between the marks were measured with a high resolution traveli ng microscope. Heat-cured acrylic resin was processed by a long curing cycle of 72 degrees C for 6.5 hours, then heated to 100 degrees C for over 30 minutes and kept at 100 degrees C for 1 hour. The relined or rebased denture was allowed to cool slowly in the water bath for 48 ho urs to reach ambient temperature. The reference crosses were measured immediately after careful deflasking. Results. In the relining procedu re, all incisor-molar and intermolar distances exhibited shrinkage of 0.3%, despite different shapes of maxillary and mandibular dentures. R esults of the rebasing procedure were similar to that of the reline ex cept that only 0.1% intermolar shrinkage was found on the maxillary de nture. Conclusion. Shrinkage was approximately 0.15 mm for an interarc h distance of 50 mm. This degree of change is both clinically undetect able and insignificant. Using this processing cycle for acrylic resin in reline or rebase procedures did not cause clinically significant di mensional changes to complete dentures.