Effects of Hard Gum Chewing on Facial Soft Tissue Morphology

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.

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 (\