Effects of Hard Gum Chewing on Facial Soft Tissue Morphology

Official title

The Effect of Intentional Hard Gum Chewing on Facial Morphology: a 3DMD-based Analysis x

Overview

This pilot clinical trial will evaluate whether intentional chewing of a standardized hard chewing gum for 4 weeks produces measurable changes in facial morphology in healthy adults. Twenty participants aged 20-40 years will undergo three-dimensional facial imaging (3dMD) at baseline (T0), after the 4-week chewing intervention (T1), and following a 4-5-week washout period (T2). Changes in facial soft-tissue morphology will be assessed using three-dimensional surface analysis, including heatmaps, regional surface displacement, and morphometric measurements. Secondary outcomes include self-reported muscle fatigue, soreness, adherence, and temporomandibular disorder (TMD) symptoms.

Detailed description

Facial morphology is influenced by multiple functional factors, including masticatory muscle activity. Although hard gum chewing has been promoted as a method to improve facial definition and jawline appearance, there is limited scientific evidence demonstrating whether intentional chewing can produce measurable changes in facial soft tissues.

The purpose of this prospective pilot clinical trial is to evaluate the effect of intentional hard gum chewing on facial morphology using three-dimensional stereophotogrammetry (3dMD). Twenty healthy adults aged 20-40 years will be enrolled. Participants will complete a standardized hard-gum chewing protocol every other day for 4 weeks. Each chewing session will last approximately 16 minutes and will follow a predefined protocol designed to provide a consistent masticatory stimulus.

Three-dimensional facial images will be obtained at baseline (T0), immediately after the intervention period (T1), and after a 4-5-week washout period (T2). Facial changes will be assessed through surface registration techniques, heatmap analysis, regional displacement measurements, and linear and angular soft-tissue measurements. Participants will also complete questionnaires regarding muscle fatigue, soreness, oral behaviors, and temporomandibular symptoms.

The primary objective is to determine whether intentional hard gum chewing produces measurable changes in facial morphology. Secondary objectives include evaluating participant-reported outcomes and monitoring for adverse events or symptoms suggestive of temporomandibular disorders.

Because this is a pilot study, the results will be used to estimate effect sizes and feasibility for future larger clinical trials investigating the relationship between masticatory activity and facial soft-tissue adaptation.

Interventions

• Behavioral Hard Gum Chewing
  Participants will chew a standardized hard chewing gum (Jawliner®, hard hardness level) every other day for 4 weeks. Each session will consist of two 8-minute chewing blocks following a standardized protocol with controlled chewing pace, progressive force application, and alternating chewing sides. Total chewing time per session will be approximately 16 minutes.

Primary outcome measures

• Changes in Facial Morphology Assessed by 3dMD Stereophotogrammetry [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]

Secondary outcome measures (12)

• Soft-Tissue Surface Topography Changes [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Change in Body Weight [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Body Height [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Participant-Reported Muscle Fatigue, Soreness, and Facial Definition Perception [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Symptom Questionnaire [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Oral Behaviors [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Patient Health Questionnaire-4 (PHQ-4) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Jaw Functional Limitation Scale-8 (JFLS-8) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Patient Health Questionnaire-9 (PHQ-9) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Jaw Functional Limitation Scale-20 (JFLS-20) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Generalized Anxiety Disorder-7 (GAD-7) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]
• Patient Health Questionnaire-15 (PHQ-15) [Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)]

Eligibility criteria

Inclusion criteria

• Healthy, non-smoking adults.
• Age 20 to 40 years.
• Presence of a full dentition from central incisor to first molar in all four quadrants, excluding second molars.
• Stable occlusion with no ongoing orthodontic treatment or myofunctional therapy.
• Ability and willingness to comply with the prescribed hard-gum chewing regimen for 4 weeks and attend all study visits.
• Ability to provide written informed consent.

Exclusion criteria

• Age younger than 20 years or older than 40 years.
• Evident facial asymmetry from a frontal view.
• Signs or symptoms of temporomandibular disorders (TMD) according to the Diagnostic Criteria for TMD (DC/TMD).
• Less than the normal range of condylar motion during maximum opening and closing.
• Parafunctional habits such as bruxism with pain, clenching, or habitual gum chewing for more than 1 hour per day.
• History of major craniofacial trauma, orthognathic surgery, or congenital craniofacial anomalies.
• Ongoing orthodontic treatment or recent removal of fixed appliances (<6 months).
• Significant malocclusion or missing teeth in the anterior or premolar-first molar region that may affect mastication.
• Systemic diseases or medications affecting muscle or bone metabolism.
• Previous use of botulinum toxin (Botox) within the last 6 months or anticipated use during the study period.
• Pregnancy or lactation.
• Allergy or intolerance to the chewing gum ingredients.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

N/A

Model

Single group

Masking

Open label

Primary purpose

Basic science

Study locations

United States · 1 center

• UConn Health — Farmington

Publications

• Tzakis MG, Kiliaridis S, Carlsson GE. Effect of a fatigue test and chewing training on masticatory muscles. J Oral Rehabil. 1994 Jan;21(1):33-45. doi: 10.1111/j.1365-2842.1994.tb01122.x. PMID 8133387
• Tzakis MG, Kiliaridis S, Carlsson GE. Effect of chewing training on masticatory efficiency. Acta Odontol Scand. 1989 Dec;47(6):355-60. doi: 10.3109/00016358909004803. PMID 2609943
• Kiliaridis S, Tzakis MG, Carlsson GE. Effects of fatigue and chewing training on maximal bite force and endurance. Am J Orthod Dentofacial Orthop. 1995 Apr;107(4):372-8. doi: 10.1016/s0889-5406(95)70089-7. PMID 7709901
• Shirai M, Kawai N, Hichijo N, Watanabe M, Mori H, Mitsui SN, Yasue A, Tanaka E. Effects of gum chewing exercise on maximum bite force according to facial morphology. Clin Exp Dent Res. 2018 Feb 22;4(2):48-51. doi: 10.1002/cre2.102. eCollection 2018 Apr. PMID 29744215

Identifiers

NCT: NCT07726511 · 26-191-1

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗