Surface characterization and force relaxation of retrieved silk sutures

To investigate the relaxation of as-received and retrieved silk sutures and characterize the compositional and structural changes occurred during service.

Silk sutures were tested in three conditions: (a) as-received, (b) retrieved from the oral cavity of patients, and (c) retrieved from extraoral sites of patients following 4 days. Specimens of the first group were fabricated by tying a knot on a plastic cable of 5 mm diameter. Specimens (n = 6) of groups (b) and (c) were placed in the appropriate surgical site and retrieved. Specimens were subjected to Fourier transform infrared spectroscopy for the characterization of molecular composition; low vacuum scanning electron microscopy (LV-SEM) to investigate the morphological variation; and energy dispersive X-ray microanalysis to assess the elemental composition of integuments formed onto the materials. To investigate the stress relaxation of elastics, a portable test assembly was developed to monitor the force exerted by a stretched suture for a period of 4 days.

Retrieved specimens demonstrated absorption of proteinaceous matter comprising of amide I and II and alcohol, as well as precipitation of Mg, Si, Cl, and Ca for the extraorally aged specimens and additional K and P for the intraorally exposed sutures. Aged specimens showed swelling and disorganization and rupture of suture bundles. Stress relaxation data were indicative of no difference between the three groups, which relaxed at 30% of the initial value, whereas the curves showed similar slopes.

Significant relaxation was found for silk sutures, which seems to be independent of surgical site.