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Objective: To evaluate the status of residual alveolar bone in aggressive periodontitis (AgP) nuclear families and to investigate the influence of teeth with root abnormity on residual alveolar bone and the heredity of root abnormity, the premolar cone-root and proportion of crown and root., Methods: Nineteen AgP probands (9 males and 10 females) at average age of 24.5 and 38 parents at average age 51.0 were included. A full set of periapical radiographs of all the subjects were taken. The residual alveolar bone of each tooth was measured by the ratio (shown as percentage) of the distance between apical and the alveolar bone crest to the whole root length. The abnormity of roots was detected on a full set of periapical radiographs. All the roots and crowns of teeth were measured. The relationship between the residual bone and the ratio was studied. The heredity grade of the premolar cone-root, proportion of crown and root, and root abnormity were computed., Results: The average residual alveolar bone of probands was less than that of their parents.In 11 families, the father's residual alveolar bone was less than that of the mother's. The average residual alveolar bone of the teeth with root abnormity was less than that of normal teeth. The average residual alveolar bone of the teeth with abnormity of roots and the normal teeth were (67.5 ± 22.2)% and (73.1 ± 18.7)% respectively, with statistical significance (P < 0.001). The heredity grade of the premolar cone-root was 40.1%, the heredity grade of proportion of crown and root was 46.8%, the heredity grade of root abnormity was 30.3%., Conclusions: The residual alveolar bone of the teeth with root abnormity was less than that of normal teeth in nuclear families. The heritability of the root abnormity, the cone-root and proportion of crown and root in our sample was 0.3-0.5, which means that genetic factors accounted for about one third to half of the efficiency for AgP.