Can a chest x-ray determine if breast implants need replacing?

There is no X-ray or MRi needed to determine if a saline implant is leaking. Saline implants harmlessly and painlessly deflate and flatten out making it obvious that there is a leak.Silicone implants, especially the newer cohesive gel implants, do not deflate when they leak. Usually a study of some sort is needed to asses whether the implant is leaking. The definitive test for a leaking silicone implant is an MRI. It would be the rare situation where a chest X-ray or mammogram would show a leaking implant.

Chest x-rays are not generally useful for detecting breast implant rupture.  If you have a rupture with a saline implant, the implant will leak (the leaking saline is harmless and will be absorbed by your body) and you will be able to see that one breast has "deflated."  Leaks can be harder to detect with silicone implants.  Today's silicone implants are made of a cohesive gel specifically designed not to leak in case of rupture.  An MRI is a good test to determine if silicone breast implants have ruptured and require replacement.