Teeth implant. Impact to nearby tooth.

My sister got a jaw fracture 4 months back. After that she got mandible surgery. Two months back the supporting strings and clips were removed. Now she wants to do teeth implant at that place, because she lost two tooth at same place. Now the x-ray photos shows there is still crack there at same place. Doctors are saying it won't be a problem with teeth implant. The said the crack would gradually go away. As I am from non medical background, I need some suggestions on this. Should we go for teeth implant or should we wait for the crack to go away. How long should we wait then for the crack to go away and do the implant. I read an article which said implant should be done as soon as possible else the jaw would gradually shrink and cause impact to nearby tooth. Thanks in advance. The x-ray photos are attached. This is current x-ray which is taken after 4 months of mandible surgery.