NUMBER AND SIZE-SPECTRA OF MYELINATED NERVE-FIBERS OF HUMAN PREMOLARS

The primary objective of this study was to determine the number and size of myelinated nerve fibers at the subcervical, midroot and juxta-apical levels of human premolars. Sixty-seven healthy premolars extracted from adolescents were utilized. Root-discs were prepared from the three sites and processed for light and electron microscopy. The myelinated nerve fibers were counted from semithin sections using a sampling microscope. The measurements were taken from composite electron micrographs using an electronic image processing unit. A total of 1883 myelinated axons from seven mandibular second premolars was gauged. The 67 teeth had an average of 312 +/- 149 myelinated nerve fibers at the juxta-apical level (range 18 to 728). The contra- and ipsilateral differences in means among the four groups of premolars were not significant (P > 0.05). The number of nerves increased significantly (P < 0.05) toward midroot and subcervical (P < 0.001) levels in all groups. The average neural diameter was 3.5 + 1.0 mum at the juxta-apical level, and the between-teeth difference in mean was found to be significant (P < 0.01). There was no decline (P > 0.05) in the diameter of myelinated nerve fibers toward midroot and subcervical levels.