How long does nerve damage from a dental implant take to heal?

Sorry to hear that. It is hard to estimate how long it will take to heal as this depends on the extent of nerve damage. Healing from nerve damage can be a slow process but it is absolutely possible to heal over time. I recommend you see an Oral Surgeon specializing in nerve damage and repair who can guide you through this.

Nerves can take quite some time to heal, often taking up to 6 months - 1 year for sensation to come back. Your dentist needs to do mapping of the numb area, and determine the type and severity of the damage. Nerve damage can be permanent, but an oral surgeon and even a second opinion will be helpful to you and can recommend next steps. Best of luck to you!

Peripheral nerves have the ability to self heal.  This means that unless the nerve was completely severed then there is a potential for healing.  The vast majority of cases heal in the first 6 months.  You may go through stages of tingling and altered sensations, but the recovery is likely.  There are cases where the numbness persists.  In these rare cases the numbing feeling does not go away.  Having a second opinion is a great idea to try and see if something else can be done.  Usually time does what nothing else can.

That's a really good question and one that is tough to answer based on minimal information. It's complicated. Nerves take a long time to heal. Depending what you mean by nerve damage, either there was just excessive pulling on the mental nerve which can cause inflammation in the region and a transient temporary type of parasthesia OR the surgeon actually drilled into the inferior dental nerve (nicked the nerve) which may take many years to heal or severed the nerve which will not ever heal. Did the surgeon use a CAT scan to assist him with the implant placement surgery? You should see another oral surgeon for a second opinion. 

I am sorry to hear you are having this problem. Unfortunately, it is somewhat unpredictable how much time it takes for complete healing. It is also possible that what you have now will be the best it gets. Not every situation heals completely.