Swiss researchers have linked dental pain relief with changes in activity and connectivity in certain parts of the brain, suggesting a distinct role for these brain regions in alleviating dental pain. The researchers presented their findings at this week's International Association for Dental Research (IADR) 2015 General Session.
In the placebo-controlled, age-matched functional MRI (fMRI) study, 28 men with a mean age of 27 years had repetitive electric stimuli applied to the left mandibular canine. This stimuli evoked an intensity perception of five on an 11-point numeric intensity rating scale.
The first phase of the experiment consisted of 30 stimuli for a duration of five minutes. Next, one group of subjects received a submucosal injection of the anesthetic articaine 4%, while another group received 0.9% sodium chloride as a placebo at the left mental foramen. In the second phase of the study, electric tooth stimulation was provided for 16 minutes; during this time, the subjects indicated pain offset by pressing an alarm ball.
In the anesthesia group, subjects reported pain relief 4.5 minutes after the injection, whereas none of those who received the placebo reported pain relief, the researchers found. An analysis between groups of the second phase showed a "significant activation cluster in the ipsilateral posterior insula (pIns)" in the placebo group, they wrote in an abstract. "Using the pIns as a seed region, the ... analysis yielded a significant enhanced coupling to the midbrain (periaqueductal grey/ventral tegmental area) after analgesia onset" in the anesthesia group only.
The findings suggest that dental pain relief was associated with a significant reduction in activity in the posterior insula, along with greater connectivity in the midbrain, the group concluded.