Chapter 6

Insight: The “geography" of attachment loss is developed by combining powerful genetic knowledge and information technology to give a new understanding about periodontitis. This approach will help clinicians determine what inherited predisposing factors may have contributed to the pattern of attachment loss. By using heritability and other genetic measures such as association with specific inherited polymorphisms, it may be possible to refine diagnostic and disease classification systems by aligning these according to subgroups of subjects that share homogeneous etiologies. This information could change the approach to treatment and prevention.

Clinical Consideration: An important clinical question: Why do different teeth succumb to periodontitis when other teeth with similar amounts of plaque, local factors and oral hygiene do not develop attachment loss?

One way to begin to address the problem of variation among teeth is to apply multivariate methods, such as principal components analysis. This method maximizes the proportion of the total variation in attachment loss among all 28 teeth explained by a limited number of master variables called principal components.

This quantitative analysis shows how attachment loss is correlated among different kinds of teeth. First molar teeth are consistently painted a yellow color by their principal components scores; these teeth are very different from all of the other teeth with regard to their patterns of attachment loss. There is a gradual change in the patterns of attachment loss for the other teeth that extend out from the central incisors (magenta) to the lateral incisors (purple), the cuspids (blue), the premolars (blue green), and the second molars (green). In addition to generally exploring patterns of periodontal disease dispersed in the “geography” of the mouth, because these are studies conducted in families, we can also use genetic epidemiologic methods to validate and compare alternative measures of disease.

Illustration of the similarities and differences among different kinds of teeth with regard to the frequency and severity of attachment loss observed in early onset aggressive periodontitis patients and their unaffected family members with the use of the principal components analysis method.13