Permanent. But must have patience and perform 2 / 3 times per week. Derma stamps work better then the rollers for scars and stretch marks.
Here's a website to review. There is also a forum that provides more information.
Dermarolling before and after photos from our customers
I am waiting on the machine, and creams recommended. I am using it to prevent wrinkles.

. I also have a few surgery scars I will treat. Looking forward to starting. Looks very positive results form research. Check out you tube vids as well.