I. What is a sulcus and sulcus caries? When we open our mouth, we can see that the occlusal surface (the side of chewing food) of the back teeth is uneven, and the sunken part is called the sulcus. If the development is not good, these sockets are very deep, food and bacteria are embedded in them, and caries (worm teeth) will occur easily, which is called sulcus caries in medicine. According to the oral epidemiological survey, more than 90% of the caries (worm teeth) of our teenagers occur in the sulcus area. What do you mean by “gutter closure”? It is a polymer composite resin material that is applied to the sulcus and cured and hardened when it flows into and penetrates the sulcus, forming a protective barrier that covers the sulcus. Third, what are the benefits of fossa closure? On the one hand, the original bacteria in the sulcus are cut off from the source of nutrition and gradually die; on the other hand, the cariogenic bacteria outside cannot enter again, thus achieving the purpose of preventing sulcus caries. Who is suitable to do the fossa closure? The method of sulcus closure is mainly used for the newly erupted permanent molars of children and adolescents to prevent caries (worm teeth). Sixth-aged teeth are the teeth that bear the most important function of chewing, because of early eruption, if not pay attention to protection, it is easy to get caries (insect tooth), so it becomes the main target of the gutter closure. Usually, six-year-old teeth are fully erupted at the age of 8-9, which is the best age for closure. Teeth with shallow sockets, front teeth and the adjacent surface of back teeth (the surface between two teeth in contact with each other), and teeth with caries (worm teeth) do not need to do sulcus closure. V. How long can the sealant last? Generally speaking, the sealant can be retained for a long time. After the closure, it is better to do a review in 3-6 months, and in the future, when doing the routine oral examination every year, the closed teeth should be checked at the same time, so as to find out whether the sealant falls off in time, so as to make up for it in time. VI. Is there any uncomfortable feeling? There is no uncomfortable feeling in the process of closure. G. Is there any harm to the teeth? Closure is a painless and non-invasive method, and the technology has been used for more than 50 years in the international arena. The use of non-toxic closure materials, no harm to the teeth, even if the closure material is swallowed off, there is no adverse impact on human health.