Soft-tissue response to silicone and poly-L-lactic acid implants with a periodic or random surface micropattern

Tissue reaction to biomaterials is dependent on properties such as surface topography. The aim of this study was to evaluate the tissue reaction around implants with different surface topographies. We made coin-shaped silicone and poly-L-lactic acid (PLLA) implants with double-sided parallel microgrooves (depth 1.0 microm; width 10.0 microm) and random roughness on a micrometer scale. The control implants were smooth. These implants were inserted into subcutaneous pockets created on the flanks of goats. After 1, 3, or 12 weeks, the goats were sacrificed and the implants retrieved and histologically processed. Light microscopic evaluation revealed the formation of fibrous tissue capsules around all implant materials. The PLLA did not visibly degrade during the study period. Histomorphometric analyses were performed on capsule thickness, capsule quality, and on the implant-tissue interface quality. Compared with the silicone implants, the capsules around the PLLA implants showed significantly better capsule quality. Compared to the smooth implants, the capsules around the microgrooved implants were thicker, but the capsules around the roughened implants were thinner. However, randomly roughened implant surfaces generally elicited a stronger and more prolonged inflammatory reaction compared to smooth and microgrooved implant surfaces. We conclude that the application of microgrooves or random surface roughness to polymer implants apparently does not have beneficial effects on peri-implant tissue healing.