The most effective treatment for acne scars by far is dermabrasion. In this treatment, a high speed brush called a fraise is used to remove the skin on the surface and to clear the way the scars are formed. This treatment is done under local anesthetic. While the superficial scars are completely removed, the deep seated ones are reduced in their depth. But dermabrasion also has certain strings attached to it. They can make the ice-pick scars more noticeable. Apart from that, dark skinned people need to undergo further treatment after dermabrasion to clear the alteration of pigmentation that it causes.
Another advanced form of dermabrasion is microdermabrasion, which is a relatively new technique in which, instead of high speed brush, aluminum oxide crystals are used. These crystals are passed through a vacuum tube and remove the skin surface. The good thing about microdermabrasion is that it removes the surface skin in a way that no additional wound is inflicted. But the negative point is that even after a few sitting in the treatment, the scars do no not disappear permanently.
Thus, even after the introduction of microdermabrasion, dermabrasion is more preferred as the results are better, disregarding the collateral damage.