Surface roughness of different contraceptive vaginal rings: evaluation by scanning electron microscope (SEM)

Objective: The aim of the study was to evaluate whether the compositions of the ethylene vinyl acetate (EVA) membrane of two different contraceptive vaginal rings could influence the surface roughness, which is associated with the possible accumulation of vaginal biomass on the rings during use. Methods: We measured and compared the surface roughness of unused vaginal rings, NuvaRing and Ornibel, using a scanning electron microscope (SEM) and dedicated software that can convert SEM images into 3D models. Average roughness (Ra), average quadratic roughness (Rq) and mean height of the irregularities at 10 points (Rz) were calculated. Results: Different thicknesses of the EVA membranes between the two rings were noted. No significant differences were found between the two rings in the three evaluated values of surface roughness (NuvaRing vs Ornibel, respectively: Ra, 1.53 ± 0.14 vs 1.61 ± 0.14 µm, p = 0.141; Rq, 2.03 ± 0.25 vs 2.07 ± 0.16 µm, p = 0.688; Rz, 11.4 ± 3.1 vs 11.4 ± 2.4 µm, p = 0.987). Conclusion: The different composition of the vaginal rings’ EVA membrane is not associated with different surface roughness. Ornibel is equivalent to NuvaRing in terms of surface roughness, despite the different composition of the membrane polymers.