Gum recession is where your teeth start to look longer.  There can be many contributing factors... but if we were to look at one jaw in silo, if the teeth are get super long looking... (gums receding)... typically that means the teeth are getting too far out of where the jawbone is.  I found a way to help address that, but it typically involves moving the supporting bone structures toward the same direction as the face of where the teeth are showing too much.

For example... someone does a stupid palatal turn rate on a maxilla... the kids' teeth shoot out too far... the gums receded and the teeth look long on the visible portion of the teeth when they smile.  This means, they got too much dental and not enough skeletal movement out.  To resolve, make the skeletal widening more.  This would be super hard to do and I wouldn't even begin to know how to do that, but the teeth need to move back toward center. 

So, I figured out this concept as I was playing with my mandibular incisors and canine teeth.  By the way, this is not a good idea to do.

Update: before teeth pop through gums, the gum tissue often lightens.   However, it takes some time for adjustments to be recognized.  I am so weird and will not and cannot recommend messing with any central incisors or canines!  They are super prone to problems.  Face pulling in general is very dangerous.