A quantitative analysis of the innervation of the pulp of the cat's canine tooth.

Although the cat's canine tooth has become the accepted model for the electrophysiological study of dental sensory mechanisms no examination of its innervation has been carried out at the electron-microscopical level. This study looked at the number and size distribution of both myelinated and non-myelinated fibers in the crown of the cat's canine. The material examined was prepared by routine methods and the measurements taken from electron-microscopical montages of pulpal cross-sections. The measurements were made using a Quantimet 720 image analysis system. In one complete cross-section 3,470 fibers were counted. Eighty-one percent of these were non-myelinated with a modal diameter of 0.35 micron. The modal diameter of the myelinated fibers was 2.5 micron. The relative preponderance of non-myelinated fibers increased from core to periphery. The largest myelinated fibers were concentrated in the core. The fiber size distribution was similar in the single complete and two partial sections examined. It is concluded that all the fibers in the crown of the cat's canine would be contained in the A-delta and C groups and that the strikingly large number of fibers present suggests that the peripheral pulp has a dense innervation, many of the cell processes found there being unsheathed axons.