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.