Since you have mentioned GC tooth mousse, that answers your first part of your question. Now comming to the second part, how does it help? Gc tooth mousse contains a very important component called Amorphous calcium Phosphate(CPP-ACP), when this is applied on the teeth, it basically adheres to the biofilm on the teeth and it enhances saliva. It basically neutralizes acidogenic bacteria that are responsible for cavity formation. Take a pea sized amount of GC mousse with a dry finger or a cotton bud and apply it to upper teeth and same amont to lower teeth as well. Use your tongue to move it in all areas. Retain it for 2 minutes and then expectorate. Do not snack or drink for atleast 30 minutes following application. Big advantage of GC mousse is its lactose free.