In one word…very! Flossing not only cleans areas of the teeth where ordinary toothbrushes can’t reach, it is a key factor in preventing gum disease. Brushing is an excellent beginning, but flossing is a crucial factor when it comes to keeping healthy teeth. The bacterium that gets caught in the nooks and crannies between teeth and in the tight spaces that toothbrushes can’t reach is removed by flossing.