There may be some difference
There may be a difference in the treated and untreated skin. Depending on your skin type, the physician may need to “feather” out to the normal areas to help blend. Depending on your hairstyle, if you wear your hear over one side of the forehead slightly, a test spot can be done there to see how you heal in relation to the surrounding skin, and if the results are acceptable then the rest of the face might not need treatment. Should a difference be noted after surgery between the two areas, the untreated area could be treated. Certainly though, the whole cosmetic unit of the temple and forehead should be treated, not just the scars themselves.
Difference in treated and nontreated skin with Fraxel Repair
Fraxel Repair is not the preferred treatment for acne scarring. Fraxel Restore has advantages and may be a better option.
Either Fraxel laser will cause some changes in the skin texture and possibly the skin coloration where treated. Your treatment will be "feathered" so that there is no discernible separation between treated and non treated skin. The fractional nature of both lasers make them far superior to the old style lasers that showed drastic differences between treated and nontreated skin. Some patients may wish to have a full face Fraxel Restore for the obvious improvements using a light setting.
Many of your treatment options will be predicated on your skin type. Patients with backgrounds that are more conducive to hyperpigmentation, such as those with Middle Eastern, Asian, American Indian or South American ancestry will need pigmentation suppression treatments to help lessen problems with post treatment pigmentation.
Fraxel Repair is more of a repair laser for skin that has sun damage. Because you are concerned with scarring, your aim is to remodel the collagen beneath and around the scars to level out the skin surface. To date this is best accomplished with the Fraxel Restore which is an erbium laser that does not actually remove skin tissue. (Fraxel Repair on the other hand, uses CO2 to vaporize microscopic columns of skin.)
A Fraxel Repair treatment would likely not provide the level of results you'd be satisfied with.
Fraxel Restore is a multi session treatment program that has advantages of multiple collagen building events. Each time your skin is treated, the skin will respond. Over time, with a number of sessions, you'll have cumulative improvements.
Fraxel Repair is typically a one-time laser treatment, carries down time and is more costly.