Effect of relining on the misfit of microwave-cured acrylic resin denture bases

Objective : The aim of this study was to evaluate the effect of microwave-energy polymerization on the accuracy and glass transition temperature of acrylic resin denture bases submitted to reline procedure. As denture wearers make up a large portion of the population and often cannot afford a new complete denture, the reline procedure may be the best alternative when indicated. Thus, it is important to evaluate possible changes that would contraindicate this technique. Materials and methods : Twenty denture bases were fabricated from microwave-cured acrylic resin (Onda-Cryl) and randomly divided into control and test groups (n = 10). In the control group, the bases were submitted to measurement of misfit. Bases in the test group were worn down internally and relined. Misfit was measured by cutting the set stone cast/denture base at three predetermined points (canine, molar and tuberosity), measuring the gap between the stone cast and the acrylic resin base at three points using the ImageTool ® software suite. Differential scanning calorimetry was used to determine Tg. Data were submitted to t-test for independent-samples (p<0.05). Results : The greatest misfit of canine sections was found at the midpoint of control group (0.280 mm); in molar sections, no significant difference was found. In maxillary tuberosity sections, the greatest misfit occurred at the midpoint of test group (0.352 mm). All gaps were below the maximal clinically acceptable misfit value. There was no significant difference in Tg values between groups. Conclusion: Microwave-energy processing does not affect the fit or Tg of relined denture bases.