The aim of this study was to test and compare the effects of microwave irradiation on the dimensional stability of two types of complete denture bases. Methodology: A prefabricated rubber mould was used for the fabrication of maxillary stone cast with four reference points and duplicated. The duplicated casts were then used for fabrication of denture bases. The study included thirty samples, which were divided into two groups of fifteen each (Group 1-Polymethylmethacrylate PMMA and Group 2- Polyamide PA). Dentures were microwaved for three minutes at 650 Watts each day while placed in distilled water. After the specimens were made, measurements were taken at one, two, and three months. To estimate the overall dimensional changes of the simulated complete dentures being tested, the percentage difference between the baseline distances of each denture base and each test group was used. The data was analysed using a 2-way repeated measures ANOVA, followed by the post hoc Tukey test. Results : When compared to the control, the Polymethyl methacrylate group shrank by 0.14% at one month; 0.18% at two months; and 0.34% at three months. The Polyamide group shrank by 0.068% after one month, 0.13% after two months, and 0.25% after three months. Statisticaly significant result was seen in PMMA after 3 months of irradiation. Conclusion: The findings indicate that the linear changes observed had no clinical significance. Microwave sterilisation of dentures is an effective alternative method

Keywords : Sterilization, Polymethymethacrylate, Polyamide, Irradiation.