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

Overview

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 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.