Around the age of 6, children begin to develop their first large teeth behind the last milk tooth, which is often referred to as the “sixth tooth”. The “sixth age” is the most important tooth among the permanent teeth, which is related to its special shape, location and pivotal function. “They play an important role in protecting the position of the upper and lower jaws. After birth, the “sixth-aged teeth” begin to calcify, and they start to erupt at the age of 5.5 to 7 years, and the permanent teeth that erupt before and after them are arranged in order according to their position. Therefore, the “sixth-age teeth” play an important role in protecting the position of the upper and lower jaws. Moreover, the “six-year-old teeth” are located in the middle of the jawbone and have a constant position in relation to the face, so it is clinically used as a sign of occlusion. If the position of “six-year-old teeth” is not normal or is lost early. The normal development of the jawbone cannot be guaranteed, and the morphology of the jawbone and the position of the teeth will then be out of order. The “six-year-old teeth” are the “backbone” of the chewing function. The “sixth-aged teeth” are the strongest multi-rooted teeth in the permanent dentition, with the largest crowns and the widest chewing area, and they bear greater biting force and chewing function than other permanent teeth. The “sixth age tooth” is the basis for the diagnosis of malocclusion. When children are 3 years old, the “sixth age teeth” are already located behind the zygomatic crest, and the first molar is located below the zygomatic crest. As the child grows older, the “sixth-age teeth” gradually move forward with the growth and development of the jaw and face. Around the age of 18, they move to below the zygomatic crest and remain for life without obvious changes. Therefore, the position of “six-year-old teeth” and zygomatic crest is often used as a basis for the diagnosis of malocclusion. However, under the influence of various pathogenic factors, “sixth-aged teeth”, the earliest permanent teeth, are the most susceptible teeth. The incidence of caries in children is higher than that of other permanent teeth, and the incidence of caries in adults is also the first. Unfortunately, many parents lack of oral health knowledge and mistakenly treat it as decayed milk teeth after the occurrence of caries in “sixth-age teeth”, and wrongly think that milk teeth will be replaced sooner or later, so it does not matter, and hope that perfect permanent teeth will grow out to replace them, so they let their caries develop, and finally the decay is serious and even be extracted. If the sixth age teeth are seriously damaged or even missing, the chewing function of children will be affected, and even cause diseases such as misalignment of teeth and asymmetric facial development. Therefore, we must do our best to protect children’s “six-age teeth”. First of all, we should help children to develop good brushing habits. Children can begin to learn to brush their teeth at the age of one and a half, parents should follow the good advice, patient teaching, and gradually help children to develop good brushing habits. Secondly, timely closure of the sulcus. By the oral surgeon to those teeth with more and deeper sulcus to carry out sulcus closure to prevent the occurrence of sulcus caries. Again, choose foods that are good for teeth and eat less foods that are harmful to teeth. Vegetables and fruits are rich in plant fiber, which can produce certain self-cleaning effect on teeth through chewing and reduce the occurrence of tooth decay. The food that is harmful to teeth is mainly sticky sugary food, after eating these food, the residual food will stick to the teeth easily, and the cariogenic bacteria in the mouth will use these food to metabolize and produce organic acid, which will act on the teeth for a long time and finally make the teeth decalcify and soften and form carious teeth. Finally, it is necessary to develop the good habit of regular examination. Children should ask the dentist to check regularly after the first milk teeth come out, once every six months, so that early detection of tooth decay can be made and early treatment can be carried out. In addition, they can also get guidance about oral health, including the correct brushing method, diet guidance, etc.