Esthetic nasolabial angle according to the degree of upper lip protrusion in an Asian population

Background: The positioning of the nasal tip is as esthetically important as the tip projection when rhinoplasty is being considered. It is not uncommon for Asians to have a protruding upper lip and teeth that affect the nasolabial angle (NLA). This study aimed to find the preferred NLA according to the degree of upper lip protrusion in an Asian population. Methods: A left-side lateral photograph of each participant was used for simulation of six different tip angles by using a photoshop program. First, the angles of the upper lip protrusion were changed into 10, 20, and 30° by a perpendicular line to the Frankfort line in each image; then, the NLAs were changed into six different angles (from 75 to 110°) for each of the three angles of upper lip protrusion for each model. Newly transformed images of nasal tips, six for the male model and six for the female model, were made by using presentation software slides and were placed in a random order. Then, 120 Korean raters were asked to choose the most preferred image from among the slides. Results: In 10° of upper lip protrusion, the preferred mean ± standard deviation (SD) NLAs for the male and female models were 88.7 ± 6.4° and 92.9 ± 6.9°, respectively. In 20° of upper lip protrusion, the preferred mean ± SD NLAs for the male and female models were 80.9 ± 6.9° and 83.9 ± 5.7°, respectively. In 30° of upper lip protrusion, the preferred mean ± SD NLAs for the male and female models were 78.4 ± 5.5° and 79.0 ± 5.4°, respectively. Conclusion: In an Asian population, the preferred NLA was changed to a more acute angle according to the degree of upper lip protrusion.