AN IMMUNOCYTOCHEMICAL STUDY OF THE INNERVATION OF DEVELOPING HUMAN FETAL TEETH USING PROTEIN GENE-PRODUCT 9.5 (PGP 9.5)

Developing teeth of 32 human fetuses (crown-rump length 11-205 mm) wer e examined immunohistochemically by antisera to protein gene product 9 .5 (PGP 9.5) in an attempt to shed light upon the possible role of inn ervation in odontogenesis. As a control for the specificity of PGP 9.5 as a neuronal marker, the results were verified by immunocytochemical co-localization in peripheral nerves of neurone-specific enolase, neu rofilaments and S-100 protein. The dental follicle received the first nerve fibres in the early cap stage. At this stage, fibroblasts differ entiated in the presence of nerve fibres and formed the dental follicl e surrounding the developing tooth. In the dental papilla, however, no fibres were demonstrated until the dentine and enamel matrices had fo rmed, about half of the present height of the tooth germ. Most nerve f ibres were localized in the basal part of the papilla until the last s tage examined and usually followed the blood vessels of the papilla. T hus the effect of innervation on tooth development may be associated w ith the development of the dental follicle. A novel finding was that f unctional odontoblasts were not only positive for S-100 but also for P GP 9.5, indicating their neural crest origin.