Many people have heard or read that rubbing your teeth with bicarbonate of soda makes them whiter. Patients even think their dentist cleans their teeth with this kind of soda. That isn't the case. The polishing powder used in the dental surgery is made of tiny spherical particles so that it doesn't scratch the surface of the tooth. Ordinary bicarbonate of soda consists of sharp little crystals. They are very rough and abrasive. If you rub your teeth with them, you wear them down prematurely. Some patients end up wearing away the enamel completely and hollowing out the surface of their teeth. Nor does this happen slowly – you may see this effect after as little as a month of use. That is why bicarbonate of soda and all abrasives must not be used on teeth.
This answer is for general information. Your own case needs an examination by an orthodontist.