"Given that facial hair growth begins at puberty and continues throughout adulthood, it is not surprising that beards augment perceptions of
maturity and
masculinity (Addison, 1989; Neave & Shields, 2008). However, associations between other personality traits and beards are highly polarized. On the one hand, bearded men are ascribed positive attributes such as
self-confidence, courage, sincerity, generosity and
industriousness (Kenny & Fletcher, 1973; Pellegrini, 1973; Hellström & Tekle, 1994). On the other hand, beards are judged as
less socially appeasing and
more aggressive (Addison, 1989; Muscarella & Cunningham, 1996; Neave & Shields, 2008)."
(Dixson & Brooks, 2013)
It's an interesting question. I always shave for interviews. If you're more comfortable with the beard, it might be worth keeping it.
My biggest concern is that they'd think you didn't care/consider the interview important enough to shave. Keep in mind your interviewer is probably going to be an old white guy, and you two may have different opinions on what's professional. It's almost a guarantee that he wore a suit and shaved when he interviewed for dental school. At the end of the day, his views are the only views that matter. There's a 0% chance that he's going to disapprove of a clean shaven face, but there's a >0% chance he's going to disapprove of the beard.
I don't really see the advantage of not shaving. It would only make me more nervous (but it might be the opposite for you).