The crown is the visible part of the dental implant and may be prone to loosening or fracture in cases of extreme pressure or stress.  While crowns, bridges and dentures attached to dental implants can be replaced, this procedure isn't as simple as replacing one that sits atop a natural tooth.  In most cases, a crown or other tooth replacement can be put back in place. However, some circumstances such as if the abutment is compromised or if the entire implant has fallen out, the entire implant will need to be replaced as soon as possible.