After maxillofacial trauma, teeth are often involved, resulting in tooth loss. Nowadays, more and more patients realize that it is possible to replant a tooth that has been lost due to trauma as long as it is treated promptly, and take the initiative to send the lost tooth to the hospital for replantation treatment. The success of dental reimplantation treatment is closely related to the way of preserving the lost tooth, and the wrong way of preserving the tooth can reduce the treatment effect of reimplantation or even the bone resorption around the reimplanted tooth. Many patients have a misconception that water, pure water or cool boiled water is clean and can be used to preserve lost teeth. The problem with this concept is that preserving a lost tooth is not only about keeping the tooth free from contamination, but also about protecting the vitality of periodontal cells attached to the root surface. As we all know, the water in human cells is not pure water, it contains many salts and proteins. When contacted with clear water (or pure water or cool boiled water) which contains very little salt, water will keep pouring into the cells, which will eventually cause the cells to rise and die. Therefore, if the deciduous tooth is preserved in water, the periodontal cells attached to the root surface will lose their vitality, die, and lose the ability to heal with the body. It is recommended that saline be used to preserve deciduous teeth. If saline is not available at home or outdoors, milk can be used to preserve the deciduous tooth. If you cannot find a suitable preservation environment, you can hold the tooth under your tongue and use saliva to temporarily preserve the lost tooth while seeking medical attention as soon as possible to create favorable conditions for tooth replantation.