tooth surface

基本解释

Low power scanning electron microscope image of tooth surface, computer-coloured yellow on blue background.
牙齿表面的电子显微镜扫描图。
Hold the floss tightly against the tooth, and move it away from the gum. Slide it firmly down the tooth surface, combining this with a back-and-forth motion.
牙线紧紧地贴着牙齿，往上向远离牙龈的方向移动，再沿着牙齿邻面向下移动，把这个动作跟牙线的前后移动组合在一块。
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 tooth surface.
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。