ABSTRACT Knife-edge or blunt root resorptions characterize ameloblastomas and are pathognomonic for this tumor, because they differentiate ameloblastomas from simple bone cysts, odontogenic keratocysts and nasopalatine duct cysts, which do not lead to resorption of involved teeth. Despite the very high frequency and importance of these characteristics for a differential diagnosis, a microscopic examination should also be conducted before defining the diagnosis and the treatment plan for these cases. This paper describes a six-step hypothesis to explain the mechanism by which ameloblastomas promote the characteristic root resorptions found in association with these benign epithelial tumors, which have a fibrous capsule formed by islands and epithelial cords that mimic the dental lamina, invade neighboring tissues and release mediators (IL-1, EGF) of tooth and root resorption. This hypothesis may be one more explanation for the tooth resorptions sometimes found in orthodontic records, and may help differentiate the root resorptions that are specific to the orthodontic practice.