Recent studies of rat incisors, in which the dental papilla has suffered different intensities of injury, showed several pathological alterations of the continuously developing teeth. FERGUSON & LAWTON  verified a well localized reaction of the dental pulp and cessation of growth for 48 hours after injury of rats' lower incisors at the dental papilla level. After rats' upper incisors luxation , there were hyperemic vessels and quick recovery of the dental pulp. On the other hand, the tissue necrosis, enamel organ atrophy and tooth germs at the dental apical third could be seen after replanting and transplanting upper incisors of rats [3, 4]. These tooth germs, dental alveolus ankylosis and mineralized masses were related by DALLESTINI, OKAMOTO, CASTRO and SANTOS-PINTO , following dental fractures in rats. The purpose of the present study is to verify histologically the behavior of the rat dental pulp and papilla, faced with a more intense injury in comparison with that cited by FERGUSON & LAWTON . Likewise, the clinical aspects of the gingival mucosa, dental crown, and growth of the same teeth are studied.