The best toothbrush head for you should allow you easy access to all surfaces of your teeth. For most adults, a toothbrush head a half-inch wide and one-inch tall will be the easiest to use and the most effective. Though there are larger toothbrush heads available, you may find it difficult to clean certain hard-to-reach areas, such as the sides and backs of your molars. The toothbrush should have a long enough handle so you can comfortably hold it in your hand.