Which of the following is a common contributing factor to TMD related to habitual jaw activity?

• A. Posture
• B. Parafunction
• C. Stress
• D. Occlusion

Answer: (B)

Parafunction refers to habitual jaw activities such as clenching and grinding the teeth, or other nonfunctional bite habits. These repetitive, excessive contractions of the masticatory muscles and repeated loading of the temporomandibular joint overload the TMJ and surrounding tissues, leading to muscle fatigue, myofascial pain, and changes in joint mechanics commonly seen in TMD. That direct link to repeated, nonfunctional jaw activity makes it the best answer. Posture or stress can influence jaw function or worsen habits but are not themselves habitual jaw activities, and occlusion concerns the alignment of teeth rather than the ongoing habits that overload the jaw.