Patterns of crowding of permanent mandibular incisors before eruption.

Observation of the radiographs taken of 37 mandibles from children ten months to seven years of age showed that the unerupted, permanent mandibular central incisors were rotated in 45 of 74 jaw halves (60.8%). The type of rotation in which the mesial aspect is directed lingually was most commonly seen (44.6%). The next most common observation was of jaw halves without any rotation of the central incisor (39.2%). The type of rotation in which the central incisor's distal aspect is turned lingually was the least common observation (16.2%). The rotation seemed symmetric in 25 jaws (67.6%).