Higher Doses of Botulinum Toxin in the Treatment of Gummy Smile
Condition: Smiling; Botulinum Toxins, Type A
Study type: Interventional
Phase: Phase 1/Phase 2

Summary: 
      Botulinum type A (BTX-A) is an easy and efficacious treatment for gingival smile (GS).
      However, the necessary for higher-doses among patients are controversial. The objective was
      to compare the reduction of gingival exposure using two methods in patients with different
      dosage. In this prospective self-controlled study, healthy GS participates who had an
      anterior gingival exposure (GE) of more than 3 mm were enrolled and administered with 2-5 U
      BTX-A (total, 4-10 U) injections into 1-2 points according to the severity presented
      pretreatment in the Average-dose Method. And after 8 months, the Higher-doses Method was
      administered the same point injection of 3-10 U BTX-A (total, 6-20 U). Data were collected at
      baseline and 4, 12, 32 and 60 weeks of follow-up.
    

Detailed description: 
      The smile is one of the universal facial expressions of humans. Gingival smile is
      characterized by gingival exposure of >3 mm upon smiling. The degree of gingival exposure can
      vary substantially between patients, with patients presenting gingival exposure of up to more
      than 10 mm. The prevalence of gingival smile is 10.57%, and it is more frequently observed in
      females. Although gingival smile is merely an anatomical variation, it can be considered
      unattractive, causing significant distress and impacting one's quality of life. Moreover,
      most orthodontists and dentists regard gingival smile as an important risk factor for dental
      treatment.

      Gingival smile involves a complex interaction between the facial muscles, bone, and skin;
      specifically, it is related to hypermobility of the upper lip with muscle involvement and
      alterations in anatomical features, such as a short clinical dental crown, anterior
      dentoalveolar extrusion, maxillary excess, and a short upper lip. Therapies for gingival
      smile range from botulinum toxin injections to surgical interventions according to its
      etiology. Although the outcomes of surgical procedures are long-lasting, botulinum toxin type
      A treatment is an easy and fast outpatient procedure that requires no downtime and has high
      efficacy rates. Nevertheless, there are controversies around the optimal dose and injection
      site of botulinum toxin type A. Moreover, the efficiency of botulinum toxin type A for
      gingival smile varies markedly between studies, with the improvement rate of gingival
      exposure ranging from 62.06% to 98%. Sucupira and Abramovitz advocate the use of a low amount
      of botulinum toxin type A of 1.95 U per side for the treatment of gingival smile. They noted
      an average satisfaction level of 9.75 on a 10-point scale with this approach. They claimed
      that higher doses does not provide further benefit, and, in fact, could lead to lip ptosis,
      asymmetry, and excessive upper lip length. However, Polo disagreed with their argument,
      claiming 2-5 U injection of botulinum toxin type A according to the severity of gingival
      smile. In this regard, Garcia and Fulton showed that low-dose injection of botulinum toxin
      per muscle (2-5 IU) was as effective as higher doses. Though prior studies have demonstrated
      a correlation between higher doses of botulinum toxin and intensity and duration of muscle
      paralyses, no conclusion can be drawn regarding duration and intensity of doses used in the
      recent studies. A safe approach advocated by some authors consists of starting with low toxin
      doses initially, with retouching at a later stage if required. In this study, the
      investigators compared botulinum toxin type A efficiency using the average-dose method (2-5 U
      botulinum toxin type A per side determined according to the severity of anterior gingival
      smile) and , the higher-dose method (3-10 U botulinum toxin type A per side determined
      according to the severity of anterior gingival smile). The investigators aimed to assess the
      efficiency and duration of these approaches, as well as side effects and patients'
      satisfaction with treatment.
    

Intervention name(s): injection of Botulinum type A
Intervention type(s): Drug
Intervention description(s): The participates were allocated to two different application methods: Simplified Method for the first injection and Individualized Method 8 months later. All the patients underwent twice injection with each methods with no change of the BTX-A(Botox, Allergan, Irvine, CA) and other injection details: Lyophilized 100 U of Botox was reconstituted in 2.5 mL of 0.9% sodium chloride solution. The injections were made with a 27-gauge insulin syringe. The treatment was an outpatient procedure and all injections were performed by one of the authors (X.G.). No anesthesia was given during the procedure.
Other intervention name(s): injection of Botulinum type A(Botox, Allergan, Irvine, CA)
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: gummy smile; botulinum toxin; dose