Can a dentist break a teeth while filling? anyone has heard about such cases?

Yes this is possible. You're dentist will tell you while he is doing the filling if it will happen and what you want to do about it, he might suggest a root canal or to just take the tooth. I klnow a root canal costs alot, and you might have to go back to see how it goes n have more work done(my grandmother n grandfather had to) Pulling it out may be cheaper, but its your choice.