Effect of Deep Freezing of High Impact Heat Activated Polymethylmethacrylate Resin on Its Flexural Strength and Impact Strength– An In Vitro Study

Abstract

Materials and Methods: Fabrication Of High Impact Heat Cure Acrylic Resin Samples was done with the help of a metal die with 65mmx10mmx3 mm dimensions metal moulds. Curing of samples was performed by using an Acrylizer PB-042, (delta) at 74°c for 2 hours following Finishing of samples using tungsten carbide burs and fine abrasive without altering the specimen surfaces and dimensions. The material in its initial dough stage transferred into an aluminium cover and placed in a plastic airtight container and stored in deep freezer at -18°C for 1 month. Total 80 samples are fabricated and divided into two groups and each group will contain 40 samples. Each group was further subdivided into two subgroups and each subgroup will contain 20 samples. The prepared 80 samples were subjected to flexural strength test and impact strength test. Test for flexural strength was conducted using Universal Testing Machine at AMS material testing lab, Hyderabad. The test for impact strength was conducted using izod impact tester.

Statistical Analysis and Results: Statistical Analysis was done with Statistical Package for Social Sciences [SPSS] for Windows Version 22.0. The flexural strength of the control group had shown a mean value of 50.062 ± 10.042 MPa, whereas the experimental group had demonstrated a higher mean value of 68.822 ± 12.290 MPa. The mean difference between the two groups was -18.761 MPa, with the 95% confidence interval ranging from -25.945 to -11.576. The impact strength of the control group had shown a mean value of 4.909 ± 0.261 kJ/m², whereas the experimental group had demonstrated a higher mean value of 7.630 ± 0.511 kJ/m². The mean difference between the two groups was -2.721 kJ/m², with the 95% confidence interval ranging from -2.980 to -2.461. The difference was statistically significant (p<0.001)

Conclusion: Authors concluded that freezing protocol had imparted structural modifications within the resin that enhanced its ability to resist deformation under bending forces and improved its resilience against sudden impacts. The results also highlighted that deep freezing of polymethylmethacrylate dough at -18°C had a positive effect on the mechanical performance of the resin. So, the incorporation of deep freezing into the preparation protocol could be considered a beneficial modification, thereby improving its overall reliability for clinical application