Backcombing, in additiong to being one of the methods of putting dreads in, is used in some situations to maintain dreads. However, re-backcombing is only recommended in hair that is COMPLETELY straight, unknotted hair at the END of a dreadlock. We also use it on particularly large strands of loose hair at the roots to help them stay 
put in the dread when I pull them in the the Loose Hair Tool. Keep your eyes out for a video on how to utilize this technique.
We can’t be clear enough that backcombing should only be used in very specific situations. Backcombing dreads that already locked and knotted only disrupts the knots and backtracks in the maturation process of the dreads. We almost hesitate to recommend anyone do this on their own dreads, but if you really think it will help you want to be 200% sure it won’t mess anything up for you. We would recommend sending us or posting on Facebook photos of the problem area to get a second, third, or even fourth opinion before taking a dread comb to any dread older than a week.