The inferior alveolar nerve was cut or the vessels entering the mandibular canal were damaged in 39 guinea pigs at 10 days of age. Possible changes in the incisors were recorded during a 100-day observation period whereafter the animals were killed and the skulls freed of soft tissues; at this time, 35 skulls were found suitable for further examination. The changes in the mandibular incisors on the operated side became observable 30–40 days post-operatively as discolourization, a ‘trauma line’ around the tooth, narrowing of the tooth or total loss of it’s visible part. In the guinea pigs with the nerve cut (group A), such signs of maldevelopment were seen in 5 out of 19 animals, whereas the corresponding figure for the animals with the damaged vessels (group B) was 14/16. All incisors in group A and 13 out of 14 in group B recovered from the state of maldevelopment; one animal in group B showed complete loss of the incisor. The molar region was examined only from the cleaned skulls. In group A, the first molar was deformed in two animals; in group B, seven animals displayed either maldevelopment of the first molar or the first and second molar or complete loss of the first molar. No malformation of the third molar was observed. With two exceptions, the deformation or loss of molars occurred in combination with incisor maldevelopment. The malformations were considered to result from a disturbed blood supply. In group A, the dental changes may perhaps be ascribed to a short-term interference with the blood supply during the operation. The variable results in group B seem to imply that the mandibular teeth receive at least part of their blood supply from vessels besides those entering the mandibular canal. The innervation appears to have a subordinate role in the restoring of the morphology of continuously eruptin