It is true that the gully closure is currently considered the best way to prevent dental caries. As a dentist, we should not mislead the parents because of the closure, and many parents mistakenly think that their children’s sixth age teeth have been closed, and they are in the safe box of caries prevention, so they should be able to rest easy. I often found some cases like this in the clinic recently, and I have to remind the majority of dental workers and parents, hope to pay attention to. The most important link of sealing is bonding, and the effect of bonding depends on the doctor’s good or bad moisture barrier during the operation. If the moisture barrier effect is not good, the bonding force will be poor, and the sealant will fall off more easily. Once the fossa sealant falls off, the incidence of dental caries will be higher than that of children who do not do fossa sealant. 2, induce temporomandibular joint disease After the closure of the fossa, the doctor needs to adjust the grinding of the sealant to remove the high point of occlusion. The author recently found in the clinic adolescent TMJ patients, they had fossa closure 1 year ago, fossa sealant significantly higher out of the occlusal surface, forming the occlusal fulcrum, after a long time, the child reversible joint disc anterior displacement symptoms appeared, the process of opening and closing the mouth appeared popping, and even headache, the child is very painful. This would not be coincidental, right? Here it is necessary to remind parents: a. Try to perform the fossa closure in the hospital to ensure the effect of the operation: isolate the moisture adequately; fine tuning and fine grinding. b. Review every six months after fossa closure to check if the fossa sealant is still in place, it is more important to find the same doctor to check.