IMMUNOCYTOCHEMICAL DETECTION OF APOPTOSIS IN HUMAN ODONTOBLASTS

Pulpal chamber size decreases on ageing due to primary and secondary d entin deposition. This work was designed to find out the consequences of this pulp chamber reduction on odontoblast number and distribution. Twenty-one healthy human premolars were equally divided into three gr oups from 11-, 12.5- and 14-yr-old adolescents, respectively). The ext ernal and the internal perimeters of dentin were recorded on vestibulo -lingual sections, from buccal to lingual cemento-enamel junction usin g an image analysis system. Nuclei of the odontoblasts were recorded o n 12 automatically selected fields. On nine erupted premolars (3 teeth from each 11-, 12.5- and 14-yr-old patients), apoptosis was detected by confocal microscopy using a modification of the original TUNEL meth od. Apoptotic cells were labeled in central pulp fibroblasts, perivasc ular endothelial cells, and in odontoblasts. When the pulp volume decr eases due to primary dentin production, the decrease of the surface av ailable for odontoblasts in compensated for by a multilayer distributi on of cells. Secondary dentin deposition, associated with odontoblasts reorganization in a single layer, results in a hyperbolic decrease of the odontoblasts number. This decrease seems to result from a program med cell death, which eliminates half of the odontoblasts over a 4-yr period.