Physicochemical and Mechanical Characterization of Silk and PGLA Dental Sutures Following Humic-Acid-Containing Surface Treatment

Surface coating may influence the physicochemical and mechanical properties of surgical sutures. This study was conducted to characterize the changes associated with a humic-acid-containing alginate coating applied to silk and poly(glycolide-co-lactide) (PGLA) sutures in two sizes (3-0 and 4-0). Untreated sutures served as controls. Surface-related spectral changes were examined using Fourier-transform infrared (FTIR) spectroscopy, while mechanical properties were evaluated via tensile testing in accordance with EN ISO 2062. Maximum tensile force and elongation at break were recorded. FTIR analysis revealed changes in the intensity and breadth of selected absorption bands, particularly those associated with O–H and C=O groups, after the coating was applied. These findings indicated treatment-associated spectral changes but did not independently confirm humic acid incorporation or coating stability. The maximum tensile force was lower in treated silk sutures than in untreated controls for both size 3-0 (22.6 ± 3.68 N vs. 17.8 ± 1.35 N; p = 0.140) and size 4-0 (12.8 ± 1.21 N vs. 10.6 ± 2.56 N; p = 0.276), although neither difference was statistically significant. For PGLA sutures, no statistically significant difference was observed for size 3-0 (27.7 ± 2.80 N vs. 27.6 ± 2.56 N; p = 0.966). In contrast, the size 4-0 PGLA sutures exhibited a higher maximum tensile force following treatment (14.2 ± 1.85 N vs. 21.1 ± 2.45 N; p = 0.021). Elongation at break increased in the treated size 3-0 silk sutures (16.0 ± 0.91% vs. 20.3 ± 1.10%; p = 0.007) and decreased in the treated size 4-0 silk sutures (19.3 ± 1.26% vs. 14.8 ± 1.75%; p = 0.027). No statistically significant differences in elongation were found for size 3-0 PGLA (32.1 ± 1.16% vs. 28.4 ± 2.21%; p = 0.082) or size 4-0 PGLA sutures (31.4 ± 1.88% vs. 30.8 ± 1.24%; p = 0.672). These preliminary findings indicate that the humic-acid-containing alginate coating procedure was associated with spectral changes and different mechanical responses in silk and PGLA sutures.