Prolonged Jaw Opening Promotes Nociception and Enhanced Cytokine Expression

Area of Science:

• Neuroscience
• Oral and Maxillofacial Surgery
• Pain Research

Background:

• Prolonged jaw opening is common in dental procedures.
• The masseter muscle's nociceptive sensitivity and cytokine expression are not well understood in this context.

Purpose of the Study:

• To investigate if prolonged jaw opening increases masseter muscle nociceptive sensitivity.
• To determine if prolonged jaw opening alters cytokine expression in relevant neural pathways.

Main Methods:

• Rats underwent prolonged jaw opening using a surgical retractor for 20 minutes.
• Head-withdrawal responses to mechanical stimuli were measured.
• Cytokine levels in the upper cervical spinal cord were analyzed using protein antibody microarrays.

Main Results:

• Jaw opening significantly increased nociceptive responses for up to 7 days.
• Differential cytokine expression in the trigeminal ganglion and spinal cord persisted for 14 days.
• Nociceptive response returned to baseline after 14 days.

Conclusions:

• Near-maximal jaw opening can sensitize trigeminal neurons, leading to nociceptive behavior.
• This sensitization may contribute to temporomandibular disorders (TMD) after dental procedures.
• Findings offer a potential explanation for TMD development post-dentistry.