On the symmetry of periodontal disease

Symmetry is a common feature of biological systems, and can be observed in multiple aspects of the human body. The purpose of this study was to estimate the impact of symmetry on variance observed in intraoral topographic distribution patterns of chronic periodontitis.

This analysis was performed on a data set from 56 subjects, including clinical and microbiological variables, recorded at the mesial and distal aspect of every tooth in the entire dentition. The impact of contralateral conditions was determined on the level of the site, the tooth, and the quadrant.

Significant correlations were detected between probing depths, recession, attachment levels, total cultivable bacterial counts and the plaque index recorded on the right and left side on all levels of analysis. The odds for bleeding on sampling, as well as for the presence of P. intermedia/nigrescens and A. actinomycetemcomitans increased significantly if the respective contralateral site was positive for the same parameter. In combining ipsilateral and contralateral parameters into the analysis it could be shown in several instances that this contralateral effect was stronger than the impact of other, ipsilateral factors. As an example, the odds for bleeding on sampling increased up to 10 fold if the contralateral site was bleeding, whereas the ipsilateral total cultivable count, determined at the same site, explained less than 30% of the variation in the bleeding tendency.

These findings support the view that the development of periodontal disease in any site cannot be explained by the influence of local detrimental factors alone.