The relationship between Peppermint oil immersion and the hardness of resin

Aim of the study: This study aimed to evaluate the effect of peppermint oil immersion on the surface hardness of polymethyl methacrylate (PMMA) acrylic resin after different immersion periods (1 day, 1 week, and 3 weeks). Materials and methods: Twenty rectangular samples were set up and split up into two groups, each group had 10 samples, first group was immersed in distilled water and second group was immersed in peppermint oil solution. They included three different periods: one day, one week, and three weeks. A daily immersion routine was adhered during these immersion times. This included immersing for eight hours in the immersion solution and then for sixteen hours in artificial saliva, all specimens were tested by hardness tester. The statistical analysis was used for the data and the comparison among all groups was obtained using analysis of variance test (two-way ANOVA-test) among all groups regarding the different immersion solutions in three different immersions periods. Further analysis was used post hoc comparisons Tukey-test to determine where the differences exist among groups at different times. In addition, Student’s t-test was used for comparisons between the two-immersion media at each time interval. Results: The descriptive statistic revealed that there is an increase in surface hardness after immersion in distilled water and peppermint oil for three weeks, as the results of immersion in distilled water after three weeks (74.70) and the results of immersion in peppermint oil after three weeks was (75.10), but the two-way ANOVA indicated there was no significant interaction regarding immersion time of acrylic resin and both solutions, but there was a significant variation was detected regarding to immersion groups across time points. As well as, the Student’s t-test revealed a significant difference was found between distilled water and peppermint oil after 1 day of immersion but there were no statistically significant differences were observed between the two-immersion media after 1 week or after 3 weeks of immersion. Conclusion: Immersion in peppermint oil and distilled water increased the surface hardness of acrylic resin. Hardness increased significantly from 1 day to later immersion times, while a difference between the two media were observed only after 1 day.