What are dermal piercings?

You could either mean dermal anchors or surface piercings. I think that you mean dermal anchors. Dermal anchors have little "feet" that are put n=beneath your skin by creating a pocket with either a needle or with the punch technique (this uses the tool that's also used for lobe and cartilage punches). The foot it placed in this pocket. The foot has holes in it that tissue will grow through to keep it in place. The dermal anchor has a threaded hole that you use to change jewelry. Dermal anchors are lots of work because you have to be very careful that they don't reject or get snagged on something and ripped out. If done correctly, the jewelry will be flush with your skin and the foot of the anchor is not visible. The jewelry can be screwed off and you can wear balls, gems, or flat pieces in them.