I don't know if there are any verified cases of people receiving radio signals through metal plates or braces. I looked on the web, but most of what I saw didn't look very credible.
A radio receiver can be very simple. In order to receive AM radio you must have four things: an antenna, a rectifier, a filter, and a speaker. I imagine it is possible that these could occur accidentally near a metal implant. One scenario might be that your bones or circulatory system are good enough conductors to act as an antenna, which gets coupled to the metal implant by way of a semiconductive coating or tissue. The metal implant might then vibrate slightly in response to the signal and create sound.
The resulting sound would be very quiet. Probably only audible to the person with the metal implant, and only if the implant were close to their ear.
Further, you would not be able to choose a 'station'. Instead, you would most likely receive whatever signals were loudest within some band of frequencies.
I found an interesting article about crystal radio sets on the web which shows some very simple radio designs. It seems possible that something like this could happen by accident.


freeweb_1
freeweb_2

I looked a little around the web.I wouldn't consider most of what I found "well documented." So, I don't know. I searched using the phrase "dental fillings and radio." I suppose that metallic fillings could work as an antenna but then what is probably a very small signal has to be detected by the teeth or jaw somehow and then sent to the brain.


I did find a pretty neat web site that explains how radio works:
http://www.howstuffworks.com/radio.htm.

I have heard that there have been documented cases of people receiving radio transmissions through the fillings in their teeth. I am not sure exactly what this sounds like, i.e., it's not like you hear music through your fillings, but there is probably more information out there somewhere. If you have access to a web browser you might do some more searching and you'll probably come across some more descriptive answers to you question.


I did a quick search on google.com (using the following search parameters: +radio waves + fillings) and I found a couple of interesting web sites that address this phenomenon.


http://www.gi.alaska.edu/ScienceForum/ASF4/473.html
http://neuro-www.mgh.harvard.edu/forum/HearingDisordersF/RadioSignalsThroughFilling.htm


How exactly do you think this could happen at all? Think about what radio waves are and why metal would be affected by them.