The effect of addition chitosan and tea tree oil to the heat-polymerized acrylic resin material on candida albicans i̇nhibition and surface roughness

Objective: The aim of the study was to compare the microbiological effect of adding various ratios of chitosan and tea tree oil to polymethylmethacrylate used as denture base material before and after thermal cycling and to evaluate the effect of added chitosan and tea tree oil on the surface roughness of the base material. Method: Method: In the study, acrylic specimens with a diameter of 20x10x3 mm for surface roughness testing and 10 mm diameter and 2 mm thickness for microbiology tests were prepared by adding 10% chitosan, 10% tea tree oil and 5% chitosan + 5% tea tree to heat-polymerized PMMA. Half of the samples were subjected to 5,000 cycles of thermal cycling between 5-55°C temperatures to simulate 6 months of thermal change in order to see long-term effects. A total of 176 samples were prepared to examine the effects of 4 groups before and after thermal cycling (n=11). Surface roughness (Ra) measurements were performed using a contact profilometer tester (Mitutoyo SJ-210, Minato-ku, Tokyo. Japan). For microbiology tests, the optical density of C. albicans was measured using a spectrophotometer at 24 h and 48 h after incubation at 37°C. In addition, the mixture in the test tube was spread on a petri dish containing sabaruod dextrose agar after serial dilution and colony counting was performed after 48 hours. SEM images were taken of 2 randomly selected samples from each group before and after thermal cycling. Statistical analyzes were analyzed using SPSS 25.0 (Statistical Packages of Social Sciences). Statistical significance level was accepted as p<0.05. Results: Before thermal cycling, there was a significant decrease in C. albicans growth in the chitosan and tea tree added groups compared to the control group, while there was no significant difference in surface roughness between the groups. After thermal cycling, similar C. albicans growth and roughness values were observed in the control group and the group with 10% tea tree oil and no significant difference was found. Significantly increased roughness values and C. albicans growth were observed in all groups to which chitosan was added. Conclusion: It is observed that chitosan and tea tree oil provide PMMA with effective antifungal properties in the short term and do not affect the surface roughness. With the antifungal activity ending after thermal cycling, tea tree oil did not degrade the surface properties of PMMA and C. albicans growth was similar to the control group, while chitosan increased the surface roughness and caused more C. albicans growth. Keywords: Chitosan, Tea tree oil, Polymethylmethacrylate, Candida albicans, Surface roughness