While you COULD extrude or intrude teeth using Invisalign, the most important question is SHOULD you? There are several variables to consider when deciding whether you should lengthen a short tooth, intrude a long one, or use cosmetic dentistry to resolve the discrepancy. Some of these include the length of the other teeth in the smile (the smile line), the positions of the gumline on the teeth in volved (since it will follow the tooth if you move it up and down), and the condition of the teeth involved (worn or broken). It is also important to consider what you will do to maintain the position of the tooth if you choose to move it orthodontically. Whether it is moved up or down, it always tends to move back in the direction it came from unless retained in some way. Building up the worn or broken edge of a short tooth with cosmetic dentistry may give a much faster, more stable result than braces or Invisalign (and I'm an orthodontist who loves moving teeth!). Good luck!