Thank you for your question. The lip position is influenced partly by the teeth as well as the underlying upper jaw position. In individuals with a upper jaw protrusion /dentoalveolar protrusion, changing the teeth position may not have as great an effect on the lips as changing the protrusion of the jaw. This is best assessed both clinically and as well as through a lateral cephalogram xray. Furthermore, everyone has different lip thickness that may also influence how the lips will change with a change in teeth position. Thicker lips have less change than thinner lips.
Teeth extraction and interproximal reduction (IPR) are both methods to create space to draw the teeth inwards. Teeth extraction yields about 7 times more space than IPR hence the potential to upright and retract teeth is greater with teeth extraction. As a rough guide, the upper lips may follow about 60-70% of the teeth movement, with IPR (which can yield only a maximum of 1-2mm of change) there may not be a visible change to the lip position.
However, if lip protrusion is your main concern, do communicate that to your dentist as there may be an underlying jaw protrusion which needs to be addressed. Other methods such as the use of temporary anchorage devices/mini-implants can also be considered to yield more space to retract teeth further.
Hope this helps and all the best,
Dr Priscilla Lu
Orthodontist
