An interventional study of Hard Gum Chewing in Face, sponsored by UConn Health. Recruiting at 1 site in United States. Open to participants aged 20 Years to 40 Years. Per ClinicalTrials.gov, last updated 2026-07-24.
Sponsored by UConn Health · Not applicable, Interventional, and Basic science
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.
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.
UConn Health is the lead sponsor of 187 studies on the registry; 18 are open to participants now.
Of its 10 completed or terminated interventional studies of FDA-regulated products, 7 (70%) have results posted.
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Exclusion Criteria:
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Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will perform a standardized hard-gum chewing protocol every other day for 4 weeks. Each session will last approximately 16 minutes and will follow a predefined chewing regimen. Three-dimensional facial images (3dMD) will be obtained at baseline (T0), immediately after the intervention period (T1), and after a 4-5-week washout period (T2) to evaluate changes in facial morphology.
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.
Changes in Facial Morphology Assessed by 3dMD Stereophotogrammetry
Quantification of facial morphology changes using three-dimensional stereophotogrammetry, including regional surface distance maps (heatmaps), linear and angular measurements, and global and regional RMS deviation values.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Soft-Tissue Surface Topography Changes
Evaluation of localized hypertonia and volumetric shifts using three-dimensional heatmap analysis and regional surface displacement measurements.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Change in Body Weight
Body weight will be measured in kilograms using a calibrated digital scale to monitor changes in body weight that could influence facial soft-tissue morphology.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Body Height
Standing height will be measured in centimeters using a Scale. Height will be used together with body weight to characterize participants' body size and, when applicable, to calculate body mass index.
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
Self-reported outcomes related to muscle fatigue, soreness, chewing effort, and perceived facial definition collected through study questionnaires.
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
Assessment of temporomandibular disorder symptoms using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I Symptom Questionnaire. This questionnaire is part of the standardized DC/TMD diagnostic protocol and evaluates jaw pain, headache attributed to TMD, joint noises, jaw locking, and functional symptoms. Responses are recorded as presence or absence of symptoms and do not generate a total score. Presence/absence of symptoms (Yes/No). This questionnaire does not generate a total score.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Oral Behaviors
Assessment of oral parafunctional behaviors using the Oral Behaviors Checklist (OBC), one of the DC/TMD Axis II instruments. The questionnaire consists of 21 items assessing awake and sleep-related oral behaviors. A total score ranging from 0 to 84 will be calculated, with higher scores indicating more frequent oral parafunctional behaviors.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Patient Health Questionnaire-4 (PHQ-4)
Assessment of psychological distress using the Patient Health Questionnaire-4 (PHQ-4), included as part of the DC/TMD Axis II psychosocial assessment. Total scores range from 0 to 12, with higher scores indicating greater psychological distress.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Jaw Functional Limitation Scale-8 (JFLS-8)
Assessment of jaw functional limitation using the Jaw Functional Limitation Scale-8 (JFLS-8), a DC/TMD Axis II instrument. The questionnaire evaluates limitations in mastication, jaw mobility, and verbal and emotional expression. Scores range from 0 to 10, with higher scores indicating greater functional limitation.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Patient Health Questionnaire-9 (PHQ-9)
Assessment of depressive symptoms using the Patient Health Questionnaire-9 (PHQ-9), administered as part of the DC/TMD Axis II psychosocial evaluation. Total scores range from 0 to 27, with higher scores indicating greater depression severity.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Jaw Functional Limitation Scale-20 (JFLS-20)
Assessment of jaw functional limitation using the Jaw Functional Limitation Scale-20 (JFLS-20), a DC/TMD Axis II instrument. Scores range from 0 to 10, with higher scores indicating greater functional limitation.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Generalized Anxiety Disorder-7 (GAD-7)
Assessment of anxiety symptoms using the Generalized Anxiety Disorder-7 (GAD-7), administered as part of the DC/TMD Axis II psychosocial evaluation. Total scores range from 0 to 21, with higher scores indicating greater anxiety severity.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Patient Health Questionnaire-15 (PHQ-15)
Assessment of somatic symptom burden using the Patient Health Questionnaire-15 (PHQ-15), administered as part of the DC/TMD Axis II psychosocial evaluation. Total scores range from 0 to 30, with higher scores indicating greater somatic symptom severity.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Clinical Examination
Clinical examination performed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I Examination Protocol, including mandibular range of motion (mm), pain on palpation of the temporomandibular joints and masticatory muscles, pain during mandibular movements, joint sounds, and diagnostic clinical findings. Continuous variables will be reported in millimeters, and categorical findings will be reported as present or absent.
Time frame: Baseline (T0), Post-Intervention (T1, 4-5 weeks), and Washout (T2, 8-9 weeks)
Plan to share: Yes — De-identified individual participant data may be available upon reasonable request.
Supporting information: Study protocol
Time frame: Beginning 6 months after publication and ending 5 years after publication.
Access criteria: De-identified data will be available upon reasonable request to the Principal Investigator.
Started Jun 2026 (actual). Primary completion is estimated for Jun 2028, 24 months after the start.
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