Evaluation of the Effect of Lignin on Mechanical, Water Sorption, and Antifungal Properties of Silicone Based Denture Soft Liners

This study aims to evaluate the mass change, mechanical (tensile bond strength, shore A hardness), antifungal properties, and biocompatibility of lignin-modified denture soft liner. Lignin was mixed in concentrations of 0.5, 1, and 2% with a silicone based denture liner (SBDSL), and was labeled as groups L1, L2, and L3 respectively while commercial SBDSL was rendered as control group C. To calculate the tensile bond strength, bar-shaped specimens were placed in a Universal Testing Machine under a tensile force. Tensile bond strength was calculated in MPa using the formula F/A. For Shore, A hardness, disc-shaped specimens were analyzed using a durometer. The mass change (%) of specimens (n = 5) was calculated by subtracting the initial weight of the samples (w1) from the weight of samples after water immersion (w2). The antifungal potential of lignin and the test specimens was measured using agar well and disc diffusion methods. Cell viability assay of SBDSL and their composite was performed on NIH 3T3 fibroblasts. The mean tensile bond strength values of control group C samples were significantly higher (p ≤ 0.05) than groups L1, L2, and L3. The mean shore A hardness values were significantly lower (p ≤ 0.05) for samples in groups L2 and L3 as compared to control group C. After 10 weeks, the control group C samples showed a significantly lower (p ≤ 0.05) mass change as compared to groups L2 and L3. Agar well diffusion methods demonstrated a maximum zone of inhibition for 2% lignin (22.3 ± 1.1 mm), after 24 h. Disc diffusion methods showed a significantly higher (p ≤ 0.05) antifungal potential of groups L2 and L3 as compared to control group C. The addition of a lower concentration of lignin increased the cell viability of SBDSL. In general, the addition of lignin in SBDSL improve the antifungal potential, and cell viability while hardness, tensile bond strength and percent mass change were decreased.