Prick density when single-needling scars

[nidu]

From this site's guide:

Dense needling for stretchmarks and scars

You need many more pricks than with acne scars, depending on how wide and long the scar is. The idea is
to get many more pricks in, per surface area, than a dermaroller can - and also deeper. The purpose is to
break old scar tissue and remove damaged collagen. This dense needling is called "needle abrasion".
Don't forget to needle the edges of the scar - go a little outside of the borders of the scar.

You can try to needle-abrade even raised scars but do a test first because the results with raised scars are
more unpredictable. This technique should only be used on already scarred skin, and then the effect will be
beneficial. It is a slow process but you can work on your scars whenever you have the time.

Make very many pricks per square cm / inch - just be sure not to prick the same skin more than once a
month. It should not take more than a twenty seconds per centimeter or a minute per inch (of stretch
mark/scar) when you're proficient. Don't forget to stretch the skin!

After a while you'll be able to do it quite quickly.

There's also a picture in there, but because the distance to the needled skin shown isn't clear, I can't be sure what the millimeter distance in-between the pricks are. Anyone know?

I'm thinking specifically about advice for atrophic/depressed/indented scars, not stretchmarks.

[SarahVaughter]

Prick the entire scar with rows of pricks positioned tightly next to each other without any gaps and then go over it once or twice again with the same density.
 
However, start slowly and during you initial needling, needle relatively sparsely to see how the skin reacts and how it heals. If everything is OK add on density of pricks with your next session.