An inlay is a restoration that is embedded inside a cavity to restore the form and function of a defective tooth. It differs from ordinary filling in that filling treatment is usually done with silver amalgam, light-cured composite resin, etc., which does not require the cooperation of a mechanic and can be done by the doctor independently, requiring less time and costing less. In addition to the different materials, inlays also require the cooperation of a technician and are more expensive. However, compared to filling materials, inlays have their advantages: increased strength, tighter edges, wear resistance similar to enamel, ideal adjacent contact to prevent food embedding, and restoration of good anatomical shape, achieving both functional and visual aesthetic effects. In pediatric dentistry, resin inlays are made for large defects in milk teeth or young permanent teeth, which are not only beautiful and durable, but also can restore the occlusal relationship between upper and lower teeth and maintain the jaw-gingival distance compared to simple filling. It is particularly suitable for teeth with cusps, incisors and occlusal surfaces that need to be re-established and cannot be perfectly restored with normal materials.