Is immersion in mint oil or apple vinegar solution a valid antifungal approach for acrylic soft liners?

Objectives: In-vitro assessment of the validity of immersion in mint oil or apple vinegar solutions as antifungal approach for acrylic soft liners. Materials and methods: Sixty disc-shaped specimens: 9mm in diameter and 2mm in length, and sixty cylinders: 12.5mm in diameter and 20mm in length of Vertex-Dental Heat-cured acrylic soft liner were prepared for antifungal activity and resilience measurements respectively. Specimens were divided into three groups; twenty in each, for immersion in mint oil, apple vinegar and distilled water (control). The groups were divided into four subgroups, five in each, for the different immersion periods: one day, one week, three weeks and six weeks. For each group, the daily immersion protocol was 8 h of immersion in the testing solution followed by 16 h in artificial saliva. This was repeated for each immersion period. Antifungal activity was assessed using disc diffusion method by measuring the inhibition zone for each disc twice: after 24 and 48 h incubation. Modulus of resilience was determined using a universal testing machine, where a stress-strain curve was obtained for each specimen and the area under the elastic portion of the curve was calculated. Results: A significantly higher antifungal activity was revealed following immersion in mint oil compared to apple vinegar solution. The immersion period was a significant variable for the antifungal activity measured after 24 h following immersion in either solution whereas it was an insignificant variable for the antifungal activity measured after 48 h following immersion in apple vinegar solution. A significant reduction in the antifungal activity was noted as the incubation period was increased from 24 to 48 h except after six weeks immersion in apple vinegar solution. Modulus of resilience of the acrylic soft liner was adversely affected by immersion in mint oil solution for more than one day and in apple vinegar solution for more than one week. Conclusions: Mint oil and Apple vinegar represent possible natural antifungal immersion solutions for acrylic soft liner provided that the immersion protocol is implemented properly