Sixth-age teeth are often called “sixth-age teeth” because they come in around the age of six, with four teeth on the top and bottom. They are permanent teeth that are no longer replaced, not milk teeth. It is a very powerful tooth with the greatest chewing function, and it plays a very important role in the establishment of the bite relationship between the upper and lower teeth, as well as the position of the whole mouth and the correctness of the lower third of the face. At the same time, it is also the tooth most prone to decay: because the “six-year-old teeth” erupt the earliest, there are more fissures in the sockets of the jaw surface, the mineralization degree is poor, and food is easily retained. In fact, many children’s “sixth-age teeth” are decayed soon after eruption. Many parents don’t know that this is a permanent tooth and think it will be replaced, so they don’t go for early treatment, and often when they go to the hospital for examination, the decay is already very serious, sometimes even to the point that they have to be pulled out. This can also lead to the misalignment of teeth and affect the normal development of children. This shows how important “six-year-old teeth” are to children! We must pay attention to protect it, let children develop good hygiene habits, regular checkups, find decay, and timely treatment. The best way to protect the six-year-old teeth is to do sulcus closure, to close up the sulcus point gap on the tooth surface which is most easily to be decayed, to prevent the occurrence of sulcus caries What is sulcus closure? It refers to the sealing of the sulcus without removing the tooth tissue and coating a layer of adhesive resin on it to form a protective barrier to prevent bacteria and food residue from entering the sulcus, and at the same time, the original bacteria in the sulcus will die gradually due to being cut off from nutrition, so as to prevent the occurrence of sulcus caries and stop the development of early caries. The method of closing the sulcus is very simple and does not affect eating, moreover, the material is non-toxic and harmless to human body after curing. However, it is necessary to emphasize that the closure needs to be carried out by professionals and the necessary instruments and equipment. The hallmark of successful closure is that the sealant is intact and can wear off but not fall off, so regular checks are needed and if the material falls off, it needs to be re-sealed. What kind of teeth need to be closed? Generally speaking, there are deep sulcus on the tooth surface, especially the ones that can catch the probe (including suspicious caries); 2.Patients who have caries in other teeth with the same name or have the tendency to have caries should have sulcus closure; for example, if a child’s upper left sixth tooth is decayed, then his upper right sixth tooth needs sulcus closure. 3.After the child’s teeth erupted and reached the occlusal plane, it is suitable to make a sulcus closure, usually within 4 years after eruption. 4, the best time for closure is: molar 3-4 years old, the first permanent molar 6-7 years old, the second permanent molar 11-13 years old, bicuspids 9-13 years old. For children with disabilities with poor oral hygiene, although older or teeth erupted oral time is longer, can consider relaxing the age of fossa closure.