The scars are visible because of contour and color differences vs. the surrounding normal skin. If you use fillers you will elevate the depression which is ok along as the color difference is minimal. The problem is the result is temporary. I prefer punch incisions around the inside of the indented scar. As long as most layers of the skin are still present in the indent and its diameter is only a couple of millimeters the circular punch incision heals with contraction causing the indented area to pop out. This is also effective for acne scars with similar attributes.