The purpose of the present study will be to evaluate the efficacy of a single dose of botulinum toxin (BTX) at the Yonsei point for the treatment of gummy smile (GS). In this double-blind single-site randomized clinical trial, A total number of 36 patients with gummy smile will be enrolled in the study at Peking University School and Hospital of Stomatology over a period of 12 months. Patients will be included and randomized 1:1 to two groups for BTX-A treatment at different injection point. For experimental group, Three units of onabotulinumtoxinA (BTX-A) per site (90 hemifaces) will be initially injected at the Yonsei point. For control group，the same dose of BTX will be injected into the levator labii superioris alaeque nasi muscle, and the injection point is located 3 to 5 mm lateral to each nostril, which was a classical injection point of this treatment. The patients will be then assessed at 2, 4, 12, 36 and 72 weeks postinjection. All subjects underwent standardized measurements by a single examiner, including dynamic and static measurements and a lateral cephalometric radiograph. In addition, facial photos and videos and a questionnaire of self-assessment will be obtained. The primary outcome measurement is the anterior gingival exposure measurements when the subject get an achieve full, unrestricted, spontaneous smiles 2 weeks postinjection.
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the dynamic measurements anterior gingival exposure (mm)
Timeframe: 2 weeks postinjection