If mental nerve is compressed by a chin implant, how long do I have to remove it to avoid permanent damage?

Sorry to hear about what is going on with your chin implant.  In general, nerve plasticity around the chin area is very good - usually in the worst of cases when there is a transection and cut nerve you can re-attach up to six months out with good outcomes.  The most important thing in your case is exactly what your doc is doing - addressing the situation such that it does not become a problem later on.  Best of luck on healing! There is some evidence showing high B12, acupuncture and hyperbaric oxygen can help with nerve injury healing.  I hope some of this helps! 

I am sorry that you are experiencing numbness after your chin implant! I assume since you are having your implant removed that your surgeon must agree that the implant is malpositioned and this numbness may improve with removal. In general, chin implant surgery can lead to stretching of the mental nerve and numbness or tingling which can be slow to resolve. If the nerve is compressed, it should improve with removal of the implant. Depending on the severity of the compression or injury to the nerve, the sensation may improve immediately after surgery, or it may take up to a year to recover sensation. Good luck to you!