The decision to extract, or not to extract, for any case depends on several factors, such as the facial and lip profile (e.g. are the lips protruding?) the amount of overlap or crowding of the teeth, how much the teeth are flared forward with respect to the bone, etc. Patients with a substantial overjet would more often have lips that unable to close due to the teeth which are sticking out.
In situations like this, extractions will result in a more aesthetic or pleasing outcome. With Invisalign treatment, there is a possibility to move the back teeth backwards as well to give space to bring the front teeth inwards more. (called distalization)
Your orthodontist will need to examine your teeth and bite together with your facial features, and detailed examination of your X-rays as well in order to decide on the best treatment plan for you.
The advantage of Invisalign treatment is that you can view the simulation and discuss together with your clinician, on the treatment plan you are most comfortable with.
Hope this helps. All the best!
Dr Geraldine Lee