The distance between the opening of the mouth and the base of the nose tends to be longer in males than in females and when a female mouth is open and relaxed the upper incisors are often exposed by a few millimeters.
To feminise a mouth an incision is usually made just under the base of the nose and a section of skin is removed. When the gap is closed it has the effect of lifting the top lip, placing it in a more feminine position and often exposing a little of the upper incisors.
The surgeon can also use a lip lift to roll the top lip out a little making it appear fuller.
With this procedure, we respect the nasal sill with a waveline incision according to Cronin. The orbicularis muscle is fixed to the interior nasal spine with strong sutures in order to create a nice dimple at the filtrum.
There must be an excision of skin, and muscle till the oral mucosa layer.
There is a vestibular approach possible with a push-up of the skin around the anterior nasal spine, without an external scar. But the lift is less spectacular, without an outroll of the upper lip, and with less definition of the upper lip.
I don't like combining this with a rhinoplasty. First nose, then lip surgery in a second stage.