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NCT Number: NCT07715331

Botulinum Toxin Type A Versus Cross-Linked Hyaluronic Acid Filler Myomodulation for Non-Surgical Management of Excessive Gingival Display

This randomized controlled trial compared the clinical efficacy and patient satisfaction of two non-surgical treatments for excessive gingival display (gummy smile): botulinum toxin type A (BTX-A) and cross-linked hyaluronic acid (HA) filler myomodulation. Excessive gingival display is defined as exposure of 3 mm or more of gingival tissue during maximal smiling. It affects approximately 14% of women and 7% of men and is associated with reduced self-confidence, smile suppression in social settings, and impaired quality of life. When caused by hyperactivity of the upper lip elevator muscles, it can be treated without surgery using injectable therapies. Twenty patients (18 females, 2 males; age 18-45 years) with excessive gingival display greater than 3 mm were randomly allocated 1:1 to one of two groups. Group A (n=10) received bilateral injections of botulinum toxin type A (Refinex; 5 IU per side) at the Yonsei point. Group B (n=10) received cross-linked hyaluronic acid filler (Juvederm Voluma with lidocaine; 1.0 mL total) injected at six periosteal sites around the nose and upper lip using a myomodulation technique. Participants were assessed at baseline and at 1, 3, and 6 months after treatment. The primary outcome was maximum gingival display measured in millimeters using a calibrated periodontal probe. Secondary outcomes included patient satisfaction measured by Visual Analog Scale and a 12-item questionnaire, and adverse event monitoring. Both treatments produced equivalent gingival display reductions at one month (BTX-A: 69.6%; HA: 63.0%). At six months, the HA group maintained a statistically significant 26.4% improvement while the BTX-A group showed near-complete relapse. Despite this, BTX-A patients reported higher categorical satisfaction. Both treatments had excellent safety profiles.

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Key information

Conditions

Excessive Gingival Display Esthetics, Dental Gingival Diseases Gummy Smile Mouth Diseases Periodontal Diseases Stomatognathic Diseases

Age range

18 year–45 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Faculty of Dental Medicine for Girls, Al-Azhar University

Cairo, Cairo Governorate, Egypt

About this study

Study Design: Prospective, two-arm, parallel-group randomized controlled clinical trial. Setting: Oral Diagnosis Clinic, Faculty of Dentistry, Al-Azhar University, Cairo, Egypt. Ethics: Approved by the Research Ethics Committee, Faculty of Dental Medicine for Girls, Al-Azhar University (Code: P-ME-25-02). All participants provided written informed consent. Study conducted in accordance with the Declaration of Helsinki. Randomization: Performed using the National Cancer Institute Clinical Trial Randomization Tool (https://ctrandomization.cancer.gov/), Maximal procedure, Maximum Tolerated Imbalance = 3, allocation ratio 1:1. Group A - BTX-A: Refinex (botulinum toxin type A), 5 IU per side, bilateral injection at the Yonsei point (convergence of levator labii superioris alaeque nasi, levator labii superioris, and zygomaticus minor muscles), single session, 30-gauge needle. Group B - HA Myomodulation: Juvederm Voluma with lidocaine (20 mg/mL cross-linked hyaluronic acid, VYCROSS technology), total 1.0 mL per patient, six periosteal deposits of 0.2 mL each at the piriform fossa bilaterally, anterior nasal spine, and nasal base bilaterally, 27-gauge needle. Negative aspiration confirmed before each injection. Outcome Measurement: Maximum gingival display measured by UNC-15 periodontal probe (three consecutive measurements averaged) at baseline (T0), 1 month (T1), 3 months (T2), and 6 months (T3). Patient satisfaction by Visual Analog Scale (0-10 cm) for overall smile and gingival display satisfaction. Psychosocial impact by 12-item Likert questionnaire. Adverse event monitoring at all follow-up visits. Standardized digital photography at each time point (Nikon D5600, 105mm macro lens). Statistics: SPSS v26.0. Independent-samples t-test for between-group comparisons. Paired-samples t-test for within-group comparisons. Chi-square and Fisher exact tests for categorical data. Pearson correlation for associations between gingival display reduction and satisfaction. Significance at p less than 0.05.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Excessive gingival display >3 mm during maximal smiling (measured by UNC-15 periodontal probe)
  • Age 18-45 years
  • Either sex
  • Ability to provide written informed consent
  • Availability for all follow-up visits at 1, 3, and 6 months post-treatment

Exclusion criteria

  • Chronic neurological diseases or blood coagulation disorders
  • Pregnancy or lactation
  • Immunological disease or current immunosuppressive drug therapy
  • Known sensitivity or allergy to botulinum toxin or hyaluronic acid products
  • Previous treatment for gummy smile within 12 months
  • Extreme age (outside 18-45 range) or pediatric patients

Treatment and study plan

Botulinum Toxin Type A (Refinex®)

Drug

5 International Units per side, bilateral injection at Yonsei point, single-session treatment

Cross-Linked Hyaluronic Acid Filler (Juvéderm Voluma® with Lidocaine)

Drug

20 mg/mL cross-linked HA, total 1.0 mL per patient, five periosteal injection sites; VYCROSS technology

Primary outcomes

  1. Maximum Gingival Display

    Time frame: Baseline (T0), 1 month (T1), 3 months (T2), 6 months (T3) post-treatment

    Maximum gingival display (mm) measured from the lower border of the upper lip to the free gingival margin at the right central incisor during standardised maximal smiling, using a UNC-15 periodontal probe. Three consecutive measurements taken and averaged by the same operator.

Secondary outcomes

  1. Overall Smile Satisfaction

    Time frame: Baseline (T0) and 6 months (T3) post-treatment

    Patient-reported overall smile satisfaction on a 100-mm Visual Analog Scale (0=completely dissatisfied, 10=completely satisfied)

  2. Gingival Display Satisfaction

    Time frame: Baseline (T0) and 6 months (T3) post-treatment

    Patient-reported gingival display satisfaction scored on a 100-mm Visual Analog Scale (0 = completely dissatisfied, 10 = completely satisfied)

  3. Psychosocial Impact and Treatment Satisfaction

    Time frame: Baseline (T0) and 6 months (T3) post-treatment

    12-item Likert-scale questionnaire assessing aesthetic self-perception, social smiling behaviour, and treatment endorsement including willingness to repeat and recommend the procedure

  4. Adverse Events

    Time frame: 1 month (T1), 3 months (T2), and 6 months (T3) post-treatment

    Monitoring for injection-site reactions, lip asymmetry, bruising, swelling, or other treatment-related adverse events at all follow-up visits

Sponsors and collaborators

Lead sponsor

Al-Azhar University

Other

Registry information

Official study title

A Prospective Randomized Controlled Clinical Trial Evaluating the Efficiency and Patient Satisfaction of Botulinum Toxin Type A Versus Cross-Linked Hyaluronic Acid Filler in the Management of Excessive Gingival Display

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Jul 20, 2026
Registry last updated
Jul 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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