Electron microscopic documentation of late changes in permanent fillers and clinical management of granulomas in affected patients.

Background: The manufacturers of permanent injectable fillers claim that their products are widely inert, biocompatible, atoxic, and nonimmunogenic. There are polymer gels without microparticles on the market and combination products that use collagen suspension or a hyaluronic acid gel as a vector to which polymer microspheres or polygonal particles are added. The filling effect of the polymer gels is based on the volume injected and, for the combination gels, partly on the volume injected and partly on the intended host foreign-body reaction to the microparticles.