My surgeon has also mentioned that he used to do chin implants more often (medpor) but has since stopped almost completely due to the infection rate, bone resorption, and other long term issues. He now does sliding genioplasty wth a bone graft from the illiac crest of the hip, which he told me has no long term negative effects (debatable).
However, for the jaw angles, he stated he also prefers to use bone grafts, even though the ammount of bone that "takes" is unpredictable, which can result in asymmetry. he says he prefers this because the medpor implants for jaw angles have an infection rate of about 10% (as confirmed by lestat earlier). Another surgeon he works with mentioned that, even decades later, if you get a tooth infection or anything of the sort, your implant may need to be removed, which, after soft tissue and bone integration, is a f-ing nightmare.
