Sir:
Gummy smile is a very unaesthetic and common condition defined as the exposure, while an individual is smiling, of more than 3 mm of gingival tissue.1 This is attributable to several factors, including hyperfunction of the perioral muscles (orbicularis oris, zygomaticus major and minor, depressor septi nasi, levator labii superioris alaeque nasi/anguli oris), lip length, clinical crown length, skeletal problems caused by maxillary excess,2 and delayed passive eruption resulting in gingival problems.1 Many authors have proposed surgical approaches,2 but these procedures are associated with morbidity and high cost and are time-consuming.3 Polo3,4 recently introduced the use of botulinum toxin type A under electromyographic guidance for the correction of gummy smile caused by hyperfunctional muscles. The author suggested injecting 2.5 U per side at the levator labii superioris, 2.5 U per side at the levator labii superioris/zygomaticus major sites, and 1.25 U per side at the orbicularis oris sites.2 The mean gingival exposure reduction was 5.2 mm, and at 24 weeks after treatment, the average gingival display had still not returned to the baseline values.4 Hwanga et al.5 identified a simple and reliable injection point in the middle of a triangle formed by the vectors of the levator labii superioris, levator labii superioris alaeque nasi, and zygomaticus minor—converging on the area lateral to the ala (Yonsei point) and after they measured the distance of the center of the triangle from the ala and the lip line (the line that connected both commissures). This study identified a safe, reproducible, and effective injection point for botulinum toxin type A.
The above-mentioned studies propose some valid and low-morbidity techniques, even if the results are temporary. Further trials are to be conducted to compare the effect of the treatment in different ethnic, sex, and age groups.
Alessandro Mangano, D.D.S.
Alberto Mangano, M.D.
Gravedona ed Uniti, Como, Italy
DISCLOSURE
The authors have no financial interest to declare in relation to the content of this article.
REFERENCES
1. Garber DA, Salama MA. The aesthetic smile: Diagnosis and treatment. Periodontol 2000 1996;11:18–28.
2. Mazzuco R, Hexsel D. Gummy smile and botulinum toxin: A new approach based on the gingival exposure area. J Am Acad Dermatol. 2010;63:1042–1051.
3. Polo M. Botulinum toxin type A in the treatment of excessive gingival display. Am J Orthod Dentofacial Orthop. 2005;127:214–218.
4. Polo M. Botulinum toxin type A (Botox) for the neuromuscular correction of excessive gingival display on smiling (gummy smile). Am J Orthod Dentofacial Orthop. 2008;133:195–203.
5. Hwanga WS, Hur MS, Hu KS, et al.. Surface anatomy of the lip elevator muscles for the treatment of gummy smile using botulinum toxin. Angle Orthod. 2009;79:70–77.
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