The purpose of this investigation was to study clinically as well as m
icrobiologically the effect of sibling relationship on the periodontal
condition in a young population with a relatively high prevalence of
periodontal disease and deprived from regular dental care. In this stu
dy, 23 family units consisting of 3 more siblings were evaluated. In a
ll, 78 subjects aged 15 to 25 years were included in the study. The me
an interproximal amount of loss of attachment in this population was 0
.29 mm. The individual mean ranged from 0 to 1.27 mm. In 33% of the su
bjects, greater-than-or-equal-to 1 sites with a probing depth of 5 mm
or more in conjunction with 2 mm of attachment loss were present. The
results show a significant sibship effect for: plaque, calculus, loss
of attachment, spirochetes on the tongue and in the pocket, Porphyromo
nas gingivalis on the gingiva and in the saliva and Prevotella interme
dia in the saliva. These results support the hypothesis that periodont
itis aggregates in families.