Effect of Microwave Cycles on Surface Roughness/Microhardness of Acrylic Dentures

Method: 5x5mm of acrylic specimens (N=10) were used in the analysis. Sample surface roughness (Mitutoyo) and micro hardness (Vickers) were measured to determine if the acrylic specimens are within the ADA specifications. 3 cycles of microwave disinfection were completed for duration of 3 min. All measurements were done in triplicate. Results were statistically analyzed using ONE WAY ANOVA.

Result: Surface Roughness and microhardness of control specimens were measured to be (0.029mm ± 0.021), (1089.85 MPa ±133.87) simultaneously. Upon completion of the 1^st microwave disinfection cycle (3 min) the average surface roughness was (0.031mm±0.023), P<0.8 with a micro hardness of (1257.3 MPa ± 142.28), P<0.014. By conventional criteria, the difference in microhardness is considered to be statistically significant. After additional 2 cycles of microwave disinfection (3min/cycle) the average surface roughness was (0.035mm±0.02), P<0.5 with a micro hardness of (1624MPa±193.87), P<0.01. By conventional criteria, the difference in microhardness is considered to be statistically significant.

Conclusion: This study concluded that the microwave oven is not acceptable for sterilization. This method of sterilization increased the microhardness of acrylic specimens, which may lead dentures to fracture during clinical use. Future research needs to be done to test the flexural strength of acrylic dentures to further support the findings in this research.