Even when I saw MM, he did not mention using HA even though I told him that I wanted more jaw definition and so am an obvious candidate for it, which seems strange if it so easily brings about good results. Some could say that implies a reluctance to use it. The next time I saw him, I specifically mentioned it to him, and he did say that it could be used, and I asked him whether there's a chance of infection, and he said that it has only ever happened to one person that he has treated with it, who experienced trauma to the jaw while playing soccer and so had to have it removed.
I've spoken to two other surgeons who said it won't give me any definition, although that may be because they don't have the expertise to apply it.
I've spoken to another surgeon who says he does not use it 'from experience' but without elaborating on this remark.
It is also true that not many surgeons use it (which may imply something) but then again, I've never seen a post on a jaw surgery forum saying that they had a bad experience with it so who knows.
It could simply be that its use extends the length of surgery considerably and so many surgeons don't like using it for marginal benefits or it could be that it is unsafe. I think the former is probably closer to the mark since dangers about its use would be recorded in the academic literature but the only way to find out is to actually use it. Reading studies is only going to tell you so much. At some point, you are actually going to have to find out for yourself.