An overjet is the amount that the upper teeth protrude in front of the lower teeth. If teeth stick forward at an angle then they can be retracted with invisalign. Simple. Some tooth volume can also be removed by interdental reduction between the teeth. Then the teeth are retracted back to reduce the overjet. Again, simple.
However the biggest changes come when the upper arch, which is narrower than the lower is widened. This allows the lower jaw to be freed to come forwards, which it does naturally or with the aid of twin blocks bonded to the invisalign appliance. Orthodontists experienced in orthopeadic orthodontics will rountinely build this into their treatment plans. An advantage of this, apart from the better aesthetic result is that the temporomandibular joint is aligned properly with the lower jaw.
This is advanced treatment that I routinely carry out for my patients, being particularly effective for teenagers who might have been told they need extractions or fixed braces with headgear. I have the cases to prove it works so I wonder why other orthodontists still use old fashioned methods. Still if the patients really want teeth out and braces and headgear for two years that’s fine. All referals welcome.