Will fat transfer fix mental crease?

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  In some patients, fat grafting can be performed in this area to improve a mental crease.   Make sure you specifically look
at before and after pictures of real patients who have had this surgery
performed by your surgeon and evaluate their results.   The most
important aspect is to find a surgeon you are comfortable with. I recommend
that you seek consultation with a qualified board-certified plastic surgeon who
can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Fat will help to soften the crease.  It won't eliminate it completely, but will soften its' appearance.  May need more than one injection of fat. 

Fat grafting to the labiomental fold can be done in one two ways. Fat injection grafting is the most common although the tight tissues of the labiodental fold do not usually bode well for high fat take, more than one injection session may be needed. The second approach is a dermal-fat graft placed intraorally with release of the fold skin on top of the muscle. This is more effective than fat grafting but is also more of a surgery