I am not a breast implant expert, but if I recall, silicone fell out of favor due to fears connecting the implants to mysterious immune-related diseases. However no connection between silicone breast implants and these diseases was ever borne out.
That was alleged, but IIRC, the studies showed that there was no toxicity, and that the women with leaking silicone implants didn't have a higher incidence of problems than other women their age.
