Previous work has indicated that the enamel-related periodontium (ERP) has a rote in the eruptive process of the rat tower incisor. By combining partial damage of this tissue with resection of the odontogenic organ, we examined the effect of the damage on subsequent incisor eruption. The connective tissue of the enamel-related periodontium was regenerated in less than 2 weeks, showing morphology close to normal. The injured part of the enamel organ was neither regenerated nor repaired, and a cement-like tissue, continuous with the true acellular cement, was formed on the denuded enamel. Before tooth exfoliation, the operated teeth erupted at a slower rate compared with root-resected and sham-operated incisors, probably because of the absence of a substantial part of the enamel organ due to surgical. damage. As with the coronal dental. follicle and the enamel organ in rat molars, the enamel-related periodontium and the enamel organ of rat incisors may have some control. on their eruptive process. (C) 2003 Elsevier Ltd. All rights reserved.493209216