This case-control study investigates fatigue induced by prolonged gum mastication in individuals with temporomandibular disorders (TMD). The study addresses two primary questions:

How does self-reported fatigue, measured with a visual analogue scale (VAS), change during sustained chewing? How do static and dynamic surface electromyographic (sEMG) parameters evolve over the same period? Participants with TMD will be compared with healthy controls to determine group differences in perceived fatigue and EMG responses.

All participants will undergo baseline EMG assessment, then chew sugar-free gum continuously for 3 minutes, alternating sides without rest. After each 3-minute interval, static and dynamic EMG recordings will be obtained and participants will rate their fatigue on the VAS. This cycle may be repeated up to six times (maximum 18 minutes). Participants are free to stop chewing at any time if fatigue becomes intolerable.

Inclusion criteria (both groups):

• Age 19-35 years
• Chewing-gum users, even occasional
• Good general health
• Good oral health

Inclusion criteria (Healthy controls):

- no diagnosed temporomandibular joint disorders

Inclusion criteria (study group)

- diagnosed temporomandibular joint disorders

Exclusion criteria (both groups):

• Non chewing gum users
• History of neurological disorders
• History of musculoskeletal diseases
• History of facial or cervical injuries
• Presence of cervical pain
• Two or more missing teeth
• Current treatment with fixed or removable orthodontic appliances
• Active periodontal disease
• Presence of cavitated carious lesions

The study population will consist of volunteer participants recruited from the undergraduate dentistry program and postgraduate specialty training programs at the University of Milan.