This story has not officially been confirmed as true, but there are many rumours about it. Back in the day, dentist’s used lead as filling material. As with most metals, lead could serve as a possible radio antenna, and there are a few reported cases of people hearing unexplained music and talking coming straight out of their own mouth, and immediately afterwards making the conclusion that they are in fact psychotic.
One of the most notorious stories is about a famous actor named Lucille Ball. On her way home from work, she heard music coming from her own mouth, and was understandably alarmed about the source of the music, seeing as how it was coming from within her own face, and she wasn’t trying to make sounds at that time.
As the story goes, on one particular night, Lucy heard some strange non-musical repetitive tones in her mouth. Soon afterwards, she reported it to the the authorities, who promptly stared blankly at her.
Apparently, the authorities eventually came to discover that Japanese spies were operating in that area of California, and Lucy may have been intercepting those transmissions through her fillings.
There have been many other reports of people hearing radio transmission through their fillings. These cases have not been confirmed to be true, because it is pretty hard to verify if someone is hearing voices in their mouth or not. But its hard to believe that people would invent this kind of story, because it would be pretty hard to come up with something so ridiculous.