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

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

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.

Study Overview

• Status: Completed
• Conditions: Gingival Diseases; Gummy Smile; Esthetics, Dental; Excessive Gingival Display
• Intervention / Treatment: Drug: Botulinum Toxin Type A (Refinex®); Drug: Cross-Linked Hyaluronic Acid Filler (Juvéderm Voluma® with Lidocaine)

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Egypt
  • Cairo Governorate
    • Cairo, Cairo Governorate, Egypt
      • Faculty of Dental Medicine for Girls, Al-Azhar University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

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

Exclusion Criteria:

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: BTX-A Group; Participants received bilateral injections of botulinum toxin type A (Refinex®; 5 IU per side) at the Yonsei point - the anatomical convergence of the levator labii superioris alaeque nasi (LLSAN), levator labii superioris (LLS), and zygomaticus minor muscles - using an insulin syringe with a 30-gauge needle. Total dose: 10 IU.	Drug: Botulinum Toxin Type A (Refinex®); 5 International Units per side, bilateral injection at Yonsei point, single-session treatment
Active Comparator: HA Myomodulation Group; Participants received cross-linked hyaluronic acid filler (Juvéderm Voluma® with lidocaine; 20 mg/mL; VYCROSS technology) administered as five periosteal deposits of 0.2 mL each (total 1.0 mL) at: piriform fossa and anterior nasal spine bilaterally, and base of nose, using a 27-gauge needle. Negative aspiration confirmed before each injection.	Drug: Cross-Linked Hyaluronic Acid Filler (Juvéderm Voluma® with Lidocaine); 20 mg/mL cross-linked HA, total 1.0 mL per patient, five periosteal injection sites; VYCROSS technology

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum Gingival Display	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.	Baseline (T0), 1 month (T1), 3 months (T2), 6 months (T3) post-treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall Smile Satisfaction	Patient-reported overall smile satisfaction on a 100-mm Visual Analog Scale (0=completely dissatisfied, 10=completely satisfied)	Baseline (T0) and 6 months (T3) post-treatment
Gingival Display Satisfaction	Patient-reported gingival display satisfaction scored on a 100-mm Visual Analog Scale (0 = completely dissatisfied, 10 = completely satisfied)	Baseline (T0) and 6 months (T3) post-treatment
Psychosocial Impact and Treatment Satisfaction	12-item Likert-scale questionnaire assessing aesthetic self-perception, social smiling behaviour, and treatment endorsement including willingness to repeat and recommend the procedure	Baseline (T0) and 6 months (T3) post-treatment
Adverse Events	Monitoring for injection-site reactions, lip asymmetry, bruising, swelling, or other treatment-related adverse events at all follow-up visits	1 month (T1), 3 months (T2), and 6 months (T3) post-treatment

Collaborators and Investigators

• Sponsor: Al-Azhar University

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2025
• Primary Completion (Actual): February 28, 2026
• Study Completion (Actual): February 28, 2026

Study Registration Dates

• First Submitted: July 15, 2026
• First Submitted That Met QC Criteria: July 15, 2026
• First Posted (Actual): July 20, 2026

Study Record Updates

• Last Update Posted (Actual): July 21, 2026
• Last Update Submitted That Met QC Criteria: July 17, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Periodontal Diseases; Mouth Diseases; Stomatognathic Diseases; Gingival Diseases; Amino Acids, Peptides, and Proteins; Proteins; Organic Chemicals; Biological Factors; Anilides; Amides; Aniline Compounds; Amines; Acetanilides; Hydrolases; Enzymes; Enzymes and Coenzymes; Botulinum Toxins; Metalloendopeptidases; Endopeptidases; Peptide Hydrolases; Metalloproteases; Bacterial Proteins; Bacterial Toxins; Toxins, Biological; Lidocaine; Botulinum Toxins, Type A
• Other Study ID Numbers: P-ME-25-02

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No