I can feel a crack at the back of my porcelain caps - can this be repaired and how much is it likely to cost?

I had my 6 front top teeth capped 4 years ago now with 2 pieces, each holding 3 teeth, made completely out of porcelain and anchored to my own teeth. On the piece on the left hand side I can feel a thin line between 2 of the 'teeth' that can't be felt on the right hand piece. Cosmetically I am not worried as the crack is at the back of the teeth and cannot be seen at all from the front. If I go to my dentist will he be able to mend it, how much is it likely to cost, and is it likely to get worse?