Damage of the Hertwig's epithelial root sheath: effect upon root growth after autotransplantation of teeth in monkeys

Abstract The effect of damage to the Hertwig's epithelial root sheath (HERS) during autotransplantation was examined in 12 green vervet monkeys. During the transplantation of permanent incisor tooth germs, either one-half or the entire root sheath was amputated or a contusion injury made to the root sheath. Transplanted incisors served as controls, where attempts were made not to injure the HERS. After an observation period of 9 months, a histologic examination of the transplanted teeth was performed. This examination showed variations in root growth among the various experimental groups. Thus, arrested root formation with ingrowth of bone from the base of the socket was the normal finding in the groups where either the entire HERS was amputated or contused. The group with partial amputation of HERS showed formation of a new but diminutive root. The control group showed teeth with normal root formation. The development of pulp necrosis usually led to complete or almost complete arrest of root formation irrespective of group. The present study indicated that the HERS can function normally subsequent to trauma elicited by surgical separation of the follicle and the post-transplantation disturbances in nutrition. Furthermore, a regenerative potential appeared to exist in this structure, even if just a fraction of it was left intact.