Does the number of attachments change during Invisalign?

Generally, attachments are placed at the initial insertion visit or at the visit after. However, the orthodontist or dentist may request attachments to be placed on during various stages of the treatment. This is particularly true of teeth that cannot have ideally placed attachments at the initial attachment placement visit. They can also make particular requests to place attachments only as they are required for specific tooth movements.
Usually, attachments will stay on until midcourse correction or refinement. They can be removed if no longer required, or may remain if those particular teeth still require movements. Your Invisalign provider should be able to tell you about all the attachments for the initial set of trays with the approval of the first ClinCheck.