Fossa sealing is a material (harmless and self-coagulating synthetic organic polymer resin) that is applied to the cross-shaped fossa of the tooth, which penetrates into the fossa on the surface of the tooth in liquid form and cures after exposure to light. It is like putting a protective coat on the teeth to protect them from food erosion. Fissure sealing, also known as point gap fissure sealing, refers to not removing the occlusal surface of the tooth tissue, coated with a layer of adhesive resin, to protect the enamel from bacteria and metabolic products erosion, and enhance the tooth’s ability to resist caries, so as to achieve the prevention of caries, an effective caries prevention method. The optimal time for sealing is 3-4 years old for milk molar, 6-7 years old for first permanent molar, 11-13 years old for second permanent molar and 9-13 years old for bicuspid. For disabled children with poor oral hygiene, although older or teeth erupted from the mouth for a longer time, the age of fossa sealing can be considered to be relaxed.