What Is Non-Implantable Grade?
Non implantable medical silicone should be rated as Class VI liquid silicone. Medical silicone manufacturers have conducted rigorous testing of the six classes to meet the Class VI requirements. Extracts of cured liquid silicone are prepared in saline, alcohol in saline, polyethylene glycol, and vegetable oil. The extracts from cured liquid silicone (diluted in the case of the PEG extract) and blanks are injected into mice and rabbits, which are observed several times over a 72-hour period. The animals’ response to the sample extracts and the blank are compared to determine test passage. These tests of extracts are called the systemic injection test and the intracutaneous test. Cured liquid silicone that pass these two tests are compliant with USP Class V. USP Class VI includes the tests of USP Class V plus an implantation test wherein strips of the cured liquid silicone and a negative control are implanted in rabbits for a period of not less than 120 hours. Hemorrhage, necrosis, discolorations, and infections are macroscopically observed and degree of encapsulation is scored and compared with the negative control to determine test passage. For a non-implantable application, a higher grade of medical silicone can also be used.
Excerpt from: Dow Corning