Flossing range and function: The adjacent surfaces of teeth cannot be cleaned by toothbrush, so we have to scrape down the plaque on the adjacent surfaces with floss (the lip and tongue surfaces of teeth are by toothbrush rather than floss). Flossing can also remove the food stuffed between the teeth, but flossing mainly scrapes the surface of the teeth rather than hollowing out the gaps. Flossing: Intercept a piece of floss about 45 cm long and wrap one end of the floss around the second knuckle of the middle finger of one hand, about two or three turns, to hold the floss in place. At a distance of about 25 centimeters, wrap the floss around the second knuckle of the middle finger of the other hand and wrap it around two or three times as well. Loosen one loop on one side and wrap another loop on the other side, then you can take turns using the clean section. Clench the middle finger, ring finger and little finger in a fist, straighten the thumb and index finger, turn the palm over so that the palm is facing outward and the two thumbs touch each other inward and make the two thumbs and the two index fingers at right angles to each other to see if the floss can be tightened. If you can, the length of the floss between the middle fingers is correct. If not, adjust again. With your thumb in a “zan” gesture and your index finger pointing up, tighten the floss with your thumb and index finger of the other hand so that the floss is about one centimeter between the two fingers, while the two fingers are straight and nail to nail. Bring the floss into the gap between the teeth and slide it along the teeth into the gap between the teeth and gums until it meets natural resistance. Tighten the floss on the tooth surface and scrape the tooth surface with up and down movements until you hear a “squeak”. After scraping one side of the tooth, scrape the other side of the same tooth. When flossing the tooth, tense the tooth surface and make a slight “C” shape. Make sure that the contact area of the floss covers the entire adjacent surface. When you start flossing, start with the central incisors and move sequentially to the back teeth until the last side of the last tooth. For the right anterior region, use the right thumb. For the left anterior region, use the left thumb. When the thumb and index finger are paired up to the corner of the mouth, the thumb will gradually feel inconvenient. In this case, replace the thumb with the index finger, i.e., use the two index fingers in combination, flossing 1 to 2 cm between the two index fingers, with one index finger on the inside of the tooth and the other on the outside of the tooth. And hold the cheeks open at the same time, so that not only is it easy to access the back teeth area, but it does not hurt the corners of the mouth. For the anterior teeth of the lower jaw, still one thumb is paired with one index finger, at this time the index finger is adjusted from the top down, and its to be raised for the arm of that index finger hand. For the posterior teeth area of the lower jaw, the same as for the upper jaw, with a pairing of two index fingers.