Stains r normal occurrences they r basically of two types intrinsic n extrinsic, normally its extrinsic stains which appear when you r grown up they r caused by various food items which r coloured as tea, coffee, colas n such drinks they appear on front of teeth, those occurring at back r often because some iron depositing bacteria normally occurring in the mouth n come as a line just
above the gum line. Once they have occurred r difficult to remove by brushing alone n require professional help a good scaling polishing n if required bleaching
can do the trick with any dentist
is the best person to attend.