The influence of premature extractions of primary molars on the ultimate root length of their permanent successors.

Final root length of lower premolars which succeed prematurely--extracted primary molars is shortened. The proposed explanation focuses on a possible accelerated movement of the permanent tooth bud and undue environmental stress following the premature extraction of its deciduous predecessor. The degree of shortening is different in both sexes and depends on the age at which the premature extraction is performed. Girls are more affected than boys, especially in cases in which the premature extractions are performed before the age of eight yr.