Thank you for your question and for including a lateral cephalogram to help me understand your case better. From the xray that you have included, the upper and lower teeth do appear to be proclined or slanting forwards. Your lips appear to close nicely with an average to normal angle between your nose and upper lip.The angles of your lips appear to be within normal range while the teeth angulation appear to be out of the normal range. It may be that you feel that your teeth are slanting outwards and protruding.
Hence the best way to improve the angulation of the upper and lower teeth is to extract premolars to provide the space to allow the front teeth to retreat backwards and upright more. As a result of the teeth moving backwards, the lips do retreat back too and hence you will see an improvement in your side profile of the lips. However the lips often do not move back as much as the teeth do. As your lip profile is only mildly protrusive, there will be sufficient improvement in your lip profile following the retraction of the front teeth.
If you don't have much crowding in your teeth, then most of the extraction space will be used to upright your front teeth. If there is some crowding present, do note that some of the space will also be used to align the teeth.
Hope this helps and all the very best.
Dr Priscilla Lu
BDSc, MDS (Ortho)
9 Scotts Road