Effects of Dose and Injection Site for Gummy Smile Treatment With Botulinum Type A
Condition: Smiling; Botulinum Toxins, Type A
Study type: Interventional
Phase: Phase 4

Summary: 
      Botulinum type A (BTX-A) is an easy and efficacious treatment for gingival smile (GS).
      However, its dosage and injection sites effect among patients are controversial.The objective
      was to compare the reduction of gingival exposure using two methods in patients with
      different dosage and injection sites. 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 single-point injection of 2 U BTX-A per side in the Simplified Method. And after
      8 months, the Individualized Method was administered with 2-5 U BTX-A (total, 4-10 U)
      injections into 1-2 points according to the severity presented pretreatment. Data were
      collected at baseline and 4, 12, and 32 weeks of follow-up.
    

Detailed description: 
      The smile is one of universal facial expressions of the humans. Gingival smile (GS) or gummy
      smile defined as any exposure of the gingiva >2 or 3 mm upon smiling, and can substantially
      vary from patient to patient, with patients presenting gummy exposures of up to more than 10
      mm. The prevalence of GS is 10.57%, and it is more frequently seen in women. Although only an
      anatomical variation, it can be considered unattractive and cause significant distress and
      impact on one's quality of life. Moreover, most orthodontists and dentists regard GS as an
      important risk factors for dental treatment.

      GS involves a complex interaction of facial muscles, bones and skin, specifically, it is
      related to the hypermobile upper lip (HUL) by the involved muscles and alterations in
      anatomical features such as short clinical dental crown, anterior dentoalveolar extrusion,
      maxillary excess and short upper lip. Therapies for GS range from botulinum toxin injections
      to surgical interventions according to its etiology. Whereas the outcomes of surgical
      procedures are long-lasting, botulinum toxin type A (BTX-A) treatment is an easy and fast
      outpatient procedure, requiring no downtime and with high efficacy rates. Nevertheless, there
      are controversies on the dosage and injection sites of BTX-A, and the efficiency of BTX-A for
      GS treatment shows great variation in different studies, with the improvement rate of
      gingival exposure (GE) ranging from 62.06% to 98%, Sucupira and Abramovitz advocate the use
      of an average amount of BTX-A of 2 U at bilateral levator labii superioris alaeque nasi
      muscles(LLSAN) for the treatment of GS, and an average satisfaction level of 9.75 on a
      10-point scale was noted in their study. In their article, use of larger dosages and
      additional injection sites is discouraged: "Other target muscles described in the literature
      do not give any additional benefit to this application and could easily lead to lip ptosis,
      inferior lip protrusion, asymmetry, or excessive lengthening of the upper lip." Polo
      disagreed their argument. They believe that dosage and injection sites of BTX-A need to be
      individualized according to the degree of severity presented. However, no clinical study
      compared and verified their divergence, and the highly personal experience and uncertainty
      still limit the use of BTX-A for GS treatment. Some authors are of the opinion that injection
      with BTX-A is a safe and cosmetically effective treatment for GS only when performed by
      experienced practitioners. Other studies preferred to initiate the treatment with
      average-dose BTX-A injection to single sites initially, with retouching at a later stage, as
      and when required. Based on the lack of studies at the stage of creating the hypothesis for
      this study, the investigators compared the efficiency using the simplified method use of 2U
      BTX-A of at bilateral LLSAN and the individualized injection of dosage and injection sites
      according to the severity of anterior GS presented in patients, and also to assess safety and
      patients' satisfaction with the 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: Crossover Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: gummy smile; botulinum toxin; dose and injection site