The antifungal potential of cinnamon oil incorporated into a heat-polymerized soft liner

This study evaluated the effects of incorporating 1% and 2% cinnamon oil into a soft liner on the growth of Candida albicans colonies and the material's hardness. Thirty soft liner specimens were prepared for the disk diffusion and thirty for the hardness test.  In each test, the specimens were divided into three subgroups based on the concentration of cinnamon oil: A) 0% (control), B) 1%, and C) 2% by weight. Cinnamon oil was added to the monomer of a heat-polymerized soft liner. C. albicans was cultured on Mueller-Hinton agar, and the diameters of the inhibition zones around the specimens were measured. The Shore A hardness test was conducted using the Shore durometer. Statistical analysis was performed by the independent t-test, one-way ANOVA, and Tukey post-hoc test (α=0.05). The control group showed no inhibition zone. The specimens in Group C exhibited a significantly larger inhibition zone (16.72 ± 0.82 mm) than Group B (12.56 ± 0.82 mm; P < 0.001). The hardness values differed significantly among groups (P < 0.001). Group C demonstrated the highest hardness (48.54 ± 0.95), significantly greater than both Groups B (47.13 ± 0.72; P < 0.05) and A (45.23 ± 0.73; P < 0.05). Adding cinnamon oil improved the antifungal activity and hardness of the soft denture liner. Adding 2% cinnamon oil increased the hardness values to the upper limit of clinical acceptability. Therefore, the 1% concentration is recommended to balance antimicrobial efficacy and maintain optimal mechanical properties of the soft liner.