[Dentin after dentinal exposure in dog teeth].

The teeth of dogs in which the root dentin was incompletely formed were prepared so that dentin was exposed. Tetracycline was then injected and the teeth were studied for dentin formation after the periods of 18, 20, 48 and 76 weeks. After the dentin was exposed slightly, reparative secondary dentin was not formed in the pulp horn area; However, a considerable amount of dentin was formed at the walls of the pulp chambers and the root canals. No changes were noted in the pulp horn area in the prepared teeth in comparison with unprepared teeth. The results imply that dentinal changes in the pulp horn area caused by dentinal cutting are more closely related to the depth of dentinal preparation than to the age of the tooth and to the elapsed time after preparation.