Sodium channel Na v 1.7 immunoreactivity in painful human dental pulp and burning mouth syndrome.

BACKGROUND

Voltage gated sodium channels Na v 1.7 are involved in nociceptor nerve action potentials and are known to affect pain sensitivity in clinical genetic disorders.

AIMS AND OBJECTIVES

To study Na v 1.7 levels in dental pulpitis pain, an inflammatory condition, and burning mouth syndrome (BMS), considered a neuropathic orofacial pain disorder.

METHODS

Two groups of patients were recruited for this study. One group consisted of patients with dental pulpitis pain (n = 5) and controls (n = 12), and the other patients with BMS (n = 7) and controls (n = 10). BMS patients were diagnosed according to the International Association for the Study of Pain criteria; a pain history was collected, including the visual analogue scale (VAS). Immunohistochemistry with visual intensity and computer image analysis were used to evaluate levels of Na v 1.7 in dental pulp tissue samples from the dental pulpitis group, and tongue biopsies from the BMS group.

RESULTS

There was a significantly increased visual intensity score for Na v 1.7 in nerve fibres in the painful dental pulp specimens, compared to controls. Image analysis showed a trend for an increase of the Na v 1.7 immunoreactive % area in the painful pulp group, but this was not statistically significant. When expressed as a ratio of the neurofilament % area, there was a strong trend for an increase of Na v 1.7 in the painful pulp group. Na v 1.7 immunoreactive fibres were seen in abundance in the sub-mucosal layer of tongue biopsies, with no significant difference between BMS and controls.

CONCLUSION

Na v 1.7 sodium channel may play a significant role in inflammatory dental pain. Clinical trials with selective Na v 1.7 channel blockers should prioritize dental pulp pain rather than BMS.