How deep can dermabrasion go on surgical scars?

Great question! The depth is limited to the papillary dermis is the desired depth- what this means is that dermabrasion is performed until "pinpoint bleeding" occurs. Going deeper than this layer can result in scarring- so that's not good. 
Dermabrasion can be done multiple times and the cosmetic result improves each time. 
Hope this helps and God Bless!
Dr. Robb

Our treatments use combination therapy to improve the epidermis and dermis for most deep scars. The options available for acne scars depend on the character of your scars, in terms of topography and contour. We see atrophic and hypertrophic acne scars, as well as scars that have hypo and hyperpigmentation. We begin each scar evaluation with an assessment of scar quality and subtype. Our main concern is rebuilding collagen and that is why we use a HIDEF protocol that includes combination therapy. Morpheus 8, scar subcision, fibrous release, fractional laser, CO2 laser, Thulium laser, PDL Vbeam laser, and fractional resurfacing can be used in addition to TCA Cross and chemical peels to further improve skin. Patients should start Melarase AM and Melarase PM for active hyperpigmentation. Always begin with a consultation to decide whether early subcision should be started.

Best,
Dr. Karamanoukian
Realself100 Surgeon

Skin regenerates from the hair follicles, sweat glands, and sweat glands within the dermis.  Any dermabrasion that goes deep removes a portion of the dermis.  The dermis is the part of the skin that regulates body temperature, has sensory nerves, and protects the deeper structures.  There are other methods of addressing scars such as DermaPen.  This type of treatment does not remove any of the skin, but can actually increase the collagen content and help repair scars.