Why is APF (apically positioned flap) performed during implant surgery?

APF (apically positioned flap) is used to preserve as much firm gum tissue as possible at an implant site by repositioning the existing flap apically rather than discarding it. The resulting band of firm gum moves less during brushing and can make daily cleaning easier. However, APF is not needed for every implant; it may be unnecessary when enough firm gum is already present, while a free gingival graft may be more appropriate when the deficiency is greater. Before surgery, we select the method after checking ① the width of firm gum, ② tissue mobility, and ③ signs of inflammation.