That means the toothbrush handle should fit comfortably in your hand and the toothbrush head should feel comfortable in your mouth and be able to reach every toothsurface.
那就是说，牙刷柄应该合手，牙刷头应该合嘴并能刷到牙齿的每个面。
2
Low power scanning electron microscope image of toothsurface, computer-coloured yellow on blue background.
牙齿表面的电子显微镜扫描图。
3
Hold the floss tightly against the tooth, and move it away from the gum. Slide it firmly down the toothsurface, combining this with a back-and-forth motion.