Sarah turned out to be a fed member who acted as a bait so that the FBI could trace her through a so- called "positioning chip" implanted to her teeth.
1) Am I right to add so- called here?
2) Teeth or tooth?
Thanks in advance
Why would you call it "so-called" - it clearly is a positioning device since the FBI used it to trace her.
And presumably the device is very small, so is only implanted in a tooth.
ALSO ...who acted as bait...