Experimental induction of cementogenesis on the enamel of transplanted mouse tooth germs.
First and second maxillary molar tooth germs with their surrounding bone were removed from 9-day-old mice, freed of the reduced enamel epithelium, re-inserted crown downwards in their bony crypts and then transplanted in the subcutaneous tissue of hosts of the same age and litter. Grafts were removed 14 days later and prepared for light and electron microscopy. In the areas where the reduced enamel epithelium was missing, a layer of cementum-like tissue was present on the enamel surface, always associated with cells showing the typical features of cementoblasts. A thin electron-lucent layer of fine fibrillar material separated the enamel surface from the new hard tissue which was composed of densely-packed collagen mixed with a ground substance. Where the cementum-like tissue was thick, cells were trapped in a collagenous matrix. The cementogenesis on enamel was strictly dependent on the absence of the reduced enamel epithelium. Thus, when exposed to follicular tissue, the surface of immature enamel appears to exert an influence on follicular cells and stimulate cementogenesis. This hypothesis could explain the presence of overgrowths of cementum in the cervical region of tooth crowns where the reduced enamel epithelium may be particularly vulnerable.
D000818:Animals; D003739:Dental Cementum / Q000502:physiology* / Q000648:ultrastructure; D003743:Dental Enamel / Q000502:physiology* / Q000648:ultrastructure; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008963:Molar; D009940:Organoids / Q000648:ultrastructure; D014083:Tooth Germ / Q000637:transplantation*