I'm not sure of the current situation of your filled teeth but my understanding is that when there are tattoos underneath the filling the dentist (biological) can simply drill it (probably less than a 1mm). I wouldnt see an issue with it as he originally drilled the decay to put in the filling and when he places the new fill it would cover it up.
If the tatoos are on the sides of the tooth then it can pose sensitivity problem as the area would be exposed (unless there was a crown to cover it up)
Mike