The use of clear aligners and digital planning of our treatments means that in many cases we "see" things that we could hardly appreciate with fixed orthodontics.
One of them are the "back and forth" movements, also known as "round tripping", which with braces and wires were unavoidable in many cases, in which the teeth were aligned by arch expansion (either transverse or pro-inclination), and then moved to their final position perhaps after performing stripping or other forms of arch space generation.
"You have to avoid the back-and-forth." Yes, it is true. It should be avoided whenever it has only negative effects.
But, in many cases, we will need to perform it, as for example in the PIR technique described in this blog, since it provides the necessary space to flatten Spee's curve.
In any case, the important thing is to be clear that the objectives of the treatment may justify having to do it, and that avoiding this cannot be the "key" of a treatment, which can be blocked by not stopping to reflect that this should be avoided only when it does not contribute to the final result of the treatment.