Botulinum toxin type A (Botox) for the neuromuscular correction of excessive gingival display on smiling (gummy smile)

Am J Orthod Dentofacial Orthop. 2008 Feb;133(2):195-203. doi: 10.1016/j.ajodo.2007.04.033.


Introduction: Previously, botulinum toxin type A (BTX-A) (Botox; Allergan, Irvine, Calif) was shown to be effective in reducing excessive gingival display in 5 patients with gummy smiles. This study was conducted to determine whether the doses and the primary injection sites used in the pilot study for the correction of gummy smiles provide consistent, statistically significant, and esthetically pleasing results.

Methods: Thirty patients received BTX-A injections to reduce excessive gingival display. Gingival display was defined as the difference between the lower margin of the upper lip and the superior margin of the right incisor. Patients were followed at 2, 4, 8, 12, 16, 20, and 24 weeks postinjection, with changes documented by photographs and videos. At week 2, the patients rated the effects of BTX-A. A group of specialty clinicians also evaluated the effects of BTX-A.

Results: Preinjection gingival display averaged 5.2 +/- 1.4 mm in the 30 patients. At 2 weeks postinjection, mean gingival display had declined to 0.09 mm (+/- 1.06 mm) in 30 patients (t = 26.01, P <.00001). The average lip-drop at 2 weeks was 5.1 mm for 30 patients. Gingival display gradually increased from 2 weeks postinjection through 24 weeks, but, at 24 weeks, average gingival display had not returned to baseline values. Based on predictions from a third-order polynomial equation, the baseline average of 5.2 mm would not be reached until 30 to 32 weeks postinjection. Patients and specialty evaluators rated the effects of BTX-A as highly favorable.

Conclusions: BTX-A injections for the neuromuscular correction of gummy smiles caused by hyperfunctional upper lip elevator muscles was effective and statistically superior to baseline smiles, although the effect is transitory.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Botulinum Toxins, Type A / administration & dosage*
  • Facial Muscles / drug effects*
  • Female
  • Gingiva / anatomy & histology*
  • Humans
  • Injections, Intramuscular
  • Lip / drug effects
  • Male
  • Muscle Hypertonia / drug therapy*
  • Neuromuscular Agents / administration & dosage*
  • Pilot Projects
  • Smiling*


  • Neuromuscular Agents
  • Botulinum Toxins, Type A