When an implant starts moving?

moving implant indicating failed implant . do not wait for more time, it will not help. remove it.

An xray can show if the surrounding bone is deteriorating.  Also, I use an implant stability reader(ostell). It uses magnets to verify stability strength.  Unfortunately, if an implant can move, it has failed.  It needs to be removed & replaced or grafted as soon as possible.

This situation needs to be evaluated professionally in the dental office. Implants fuse to the bone, and there should be no movement between the body of the implant with the bone. This could be determined radiographically if there's been a failure. If the implant abutment portion or the crown portion have loosened, this could be corrected. However, if the implant is loose from the bone that would be a failure, and the implant would have to be removed.

Implants don't move but the restoration on the implant can move or be loose. I would return to the dentist who has the work done and ask them to take a look and see what the problems may be. 

Implants don't move, not even a little bit. This implant has failed and needs to be removed. After a period of healing, it can be redone.