Higher Doses of Botulinum Toxin in the Treatment of Gummy Smile

Phase 1

Completed

Conditions: Smiling
Botulinum Toxins, Type A

Interventions: Drug: injection of Botulinum type A

Registration Number: NCT05127018

Lead Sponsor: Peking University

Brief 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.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 33

Inclusion Criteria

≥ 3.0-mm anterior gingival exposure upon unrestricted, "full-blown" smiling
healthy adults

Exclusion Criteria

contraindication of BTX-A
previous diseases or treatments affecting the position of the gingiva or upper lips
history of BTX-A injections to the head or neck region
facial paralysis
having received and/or receiving active orthodontic treatment that includes vertical dimension treatment, such as extrusion and intrusion, and presence of
periodontal disease
subject's refusal to participate

Study & Design

Study Type: INTERVENTIONAL

Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
the average-dose method	injection of Botulinum type A	With the average-dose method, the dose was individualized according to the severity of anterior gingival exposure pretreatment. For mild gingival smile (3-5 mm), a single-site injection of 2 U botulinum toxin type A \[total, 4 U\] at both the right and left levator labii superioris alaeque nasi muscles) was administered. For moderate (5-7 mm) and severe (≥7 mm) gingival smile, 3 U and 5 U of botulinum toxin type A, respectively, were injected per side (total, 6 U and 10U, respectively). The injection points were located at bilateral levator labii superioris alaeque nasi muscles and at the Yonsei point26, with half doses administered at each point.
the higher-dose method	injection of Botulinum type A	With this method, patients were administered botulinum toxin type A after 8 months when the effect of the previous injection had vanished. The injection dose (U) per side was set as the absolute value of the preoperative anterior gingival exposure (mm). For example, if the preoperative anterior gingival exposure was 5mm, then the patient would be injected with 5 U of botulinum toxin per side (total, 10U). The injection points were located at bilateral levator labii superioris alaeque nasi muscles and at the Yonsei point26, with half doses administered at each point.

Primary Outcome Measures

Name	Time	Method
Anterior Gingival Exposure (GE) 4 Weeks Post-injection	4 weeks postinjection	The distance from the superior margin point of the right incisor to the lower margin of the upper lip upon maximum smile.

Secondary Outcome Measures

Name	Time	Method
Anterior Gingival Exposure (GE) 12 Weeks Post-injection	12 weeks postinjection	The distance from the superior margin point of the right incisor to the lower margin of the upper lip upon maximum smile.
Anterior Gingival Exposure (GE) 24 Weeks Post-injection	24 weeks postinjection	The distance from the superior margin point of the right incisor to the lower margin of the upper lip upon maximum smile.
Anterior Gingival Exposure (GE) 48 Weeks Post-injection	48 weeks postinjection	The distance from the superior margin point of the right incisor to the lower margin of the upper lip upon maximum smile.