Increase in c-fos-like immunoreactivity in the trigeminal nucleus complex after dental treatment.

An immunohistochemical study was made of the temporal changes in the expression of the c-fos oncogene protein in the spinal trigeminal nucleus complex (STNC) after three different types of dental injury. One hour after tooth extraction or pulp exposure, c-fos neurons appeared in the ipsilateral subnucleus caudalis, but there were very few c-fos neurons in the ipsilateral subnuclei oralis and interpolaris, and in the trigeminal main sensory nucleus and contralateral STNC. The great number of c-fos neurons was found 2-4 hours after injury, levels decreased by 8 hours after injury. Twenty-four hours after injury, the number of these neurons in subnucleus caudalis became very small. Shallow cavity preparation, however, did not induce an increase in the number of c-fos neurons at any selected postoperative time in STNC. These results indicate that c-fos neurons appear mainly in subnucleus caudalis very soon after severe dental injury.