A flat forehead is usually caused by a lack of fullness in the frontal bone of the skull. Fillers for forehead area can choose to fill hyaluronic acid, autologous fat or tumescent material. 1. Hyaluronic acid filling: Generally, large molecule, high density hyaluronic acid material is chosen to fill the bony structure, and the effect is more ideal. 2. Autologous fat filler: Autologous fat filler is easier to take materials, not easy to produce rejection reaction. 3. Tumescent filler: tumescent is an inert prosthetic material, stable in nature, not easy to deform and shift after filling the forehead. It is recommended that candidates who want to fill in the forehead area go to a regular hospital and choose the right material under the guidance of a professional doctor.