Objective: To propose a safe and reproducible injection point for botulinum toxin-A (BTX-A) as a supplementary method for the treatment of gummy smile, as determined by assessment of the morphologic characteristics of three lip elevator muscles. Materials and Methods: A total of 50 hemi-faces from 25 adult cadavers (male 13, female 12; ages, 47 to 88 years) were used in this study. Topographic relations and the directions of the lip elevator muscles (ie, levator labii superioris [LLS], levator labii superioris alaeque nasi [LLSAN], and zygomaticus minor [ZMi]), were investigated. Possible injection points were examined through the study of predetermined surface landmarks. Results: The insertion of the LLS was covered partially or entirely by the LLSAN and the ZMi, and the three muscles converged on the area lateral to the ala. The mean angle between the facial midline and each muscle vector was 25.8 ± 4.8 degrees for the LLS, 55.7 ± 6.4 degrees for the ZMi, and −20.2 ± 3.2 degrees for the LLSAN; no significant differences were noted between male and female subjects or between left and right sides. The three vectors passed near a triangular region formed by three surface landmarks. The center of this triangle, named the “Yonsei point”, was suggested as an appropriate injection point for BTX-A. The clinical effectiveness of the injection point was demonstrated in selected cases with or without orthodontic treatment. Conclusions: Under careful case selection, BTX-A may be an effective treatment alternative for patients with excessive gingival display caused by hyperactive lip elevator muscles.

The purpose of the present study was to determine the locations of the infraorbital foramen and mental foramen based on soft-tissue landmarks to facilitate prediction of the locations of these structures during facial surgery. Fifty embalmed cadavers (100 sides) of Koreans were dissected to expose the infraorbital foramen and mental foramen. The distances between the bilateral infraorbital foramina and between the mental foramina and the distances between the alae of the nose and between the corners of the mouth (cheilions) were measured directly on the cadavers, and the vertical and horizontal distances between the infraorbital foramen and mental foramen and the ala of the nose and cheilions, respectively, were measured indirectly on photographs. The distance between the bilateral infraorbital foramina (54.9 +/- 3.4 mm) was greater than that between the bilateral mental foramina (47.2 +/- 5.5 mm). The infraorbital foramen was located 1.6 +/- 2.7 mm lateral and 14.1 +/- 2.8 mm superior to the ala of the nose. The distance between the ala of the nose and the infraorbital foramen was 15.9 +/- 2.8 mm, and the horizontal angle between these structures was 64.1 +/- 9.9 degrees laterosuperiorly. The mental foramen was located 20.4 +/- 3.9 mm inferior and 3.3 +/- 2.9 mm medial to the cheilions. The distance between the cheilions and mental foramen was 20.9 +/- 3.8 mm, and the vertical angle between these structures was 9.2 +/- 8.1 degrees inferomedially. This study provides data that will be useful in predicting the locations of the infraorbital foramen and mental foramen when used together with hard-tissue landmarks. These data may be particularly helpful for facial surgery in patients with missing teeth.

Song WC, et al. Yonsei Med J. 2009 Apr;50(2):300-303. http://dx.doi.org/10.3349/ymj.2009.50.2.300