Comparison of Autoclave and Microwave Postpolymerization Treatments on Flexural Strength of Hard Reline Resins

Purpose: To compare the effect of autoclave and microwave post-polymerization treatments on flexural strength of hard reline and heat-polymerized acrylic resins. Material and Methods: Hard chairside reline and heat-polymerized acrylic resin specimens (64x10x3.3 mm) were fabricated. 80 specimens with 4 subgroups for each acrylic (n=20) received post-polymerization treatment by microwave irradiation and two autoclave post-polymerization modalities (short and long). Specimens were subjected to flexural strength testing using 3-point bending with a crosshead speed of 5 mm/min. Two-way, one-way ANOVA and Tukey’s HSD tests were used for statistical analysis of data. Results: The microwave post-polymerization significantly increased the strength of heat polymerized acrylic resin and hard chairside reline resin specimens where its effect was significantly higher than the autoclave and control groups (p 0.01). Both autoclave groups presented higher strength values than the control group (p 0.01). For both materials, the difference between the mean flexural strength values of short and long autoclave application was statistically insignificant (p 0.05). Conclusion: Using autoclave, may be considered as a viable post-polymerization treatment alternative in order to increase the flexural strength of relined dentures.