To understand the mechanisms of action of amelogenin splice products A+4 and A-4 and their potential as therapeutic agents in dentin repair.
Two amelogenin peptides, specific gene splice products A+4 and A-4, were adsorbed onto agarose beads and implanted via dentin perforations into the pulps of the first maxillary molars of rats for 8, 15, 30 and 90 days. Beads soaked in buffer only were used as controls.
Inflammatory processes were seen shortly after implantation, but the pulps recovered gradually. At 8 days, cells recruited by both A+4 and A-4 soaked beads formed rings around the beads, and the proliferating cell nuclear antigen (PCNA) method revealed that a proliferation centre formed in the central part of the pulp and near the perforation. Cell proliferation occurred also in the root along a sub-odontoblastic border. The cells present around the beads were stained positively by anti-osteopontin. In contrast anti-dentin sialoprotein labelled cells near the perforation, but not the cells in closest association with the bead surface. These observations suggest that post-mitotic cells differentiated into osteoblast-like, rather than odontoblast-like cells. A+4 produced a thick dentinal bridge at the perforation, whereas A-4 contributed both to the formation of reparative dentin in the coronal pulp and to the total closure of the root canal. Mineralization was restricted, even after 90 days, to the pulp and did not extend to the periodontal tissues.
These results suggest that the amelogenin peptides may be used to stimulate reparative dentin formation, and have the potential to be a substitute for endodontic treatment.
pulp, reparative dentin, amelogenin, cell differentiation