Preventive Dentistry » Bad Breath Bits of food that get caught between the teeth and on the tongue will rot and can sometimes cause an unpleasant smell. So correct and regular brushing is very important to keep your breath smelling fresh. The bacteria on our teeth and gums (plaque) also cause gum disease and dental decay. If you see your dentist regularly this will not only help prevent bad breath but will also let the dentist look for and treat these problems.