[Morphometric analysis of human pulp myelinated fibers during aging].

In view of the considerable variations in contour shapes noted in transverse sections of myelinated axons from dental pulps a morphometric method involving image analysis (TAS Leitz) was used to calculate directly the surfaces of the nerves in sections of human root pulp using the Bodian stain. The sample studies consisted of 26 patients aged 10.5 to 72 years. The variation in numbers of myelinated pulpal nerves was analysed by age. Of 3606 myelinated fibres measured, 95% had a diameter less than 5 microns (A delta fibres) and about 0.5% had a diameter greater that 7 microns (A beta fibres). The mean diameter of these myelinated fibres was 2.90 microns. The statistical analysis clearly showed a difference in distribution between these fibres in young and very old subjects. The total number of pulpar myelinated fibres decreased with age particularly at the expense of a A delta fibres. The A beta fibres remained constant. This decrease of A delta fibres with age may be related to a reduced sensitivity to the perception of dental pain transmitted by these fast-conducting A delta fibres.