Evidence of a substantial genetic basis for risk of adult periodontitis

Background: A few previous studies have suggested that risk for adult perio dontitis (AP) has a genetic (heritable) component. We estimated genetic and environmental variances and heritability for gingivitis and adult periodon titis using data from twins reared together. Methods: One hundred seventeen (117) pairs of adult twins (64 monozygotic [ MZ] and 53 dizygotic [DZ] pairs) were recruited. Probing depth (PD), attach ment loss (AL), plaque, and gingivitis (GI) were assessed on all teeth by t wo examiners. Measurements were averaged over all sites, teeth, and examine rs. Extent of disease in subjects was defined at four thresholds: the perce ntage of teeth with AL greater than or equal to2, AL greater than or equal to3, PD greater than or equal to4, or PD greater than or equal to5 mm. Gene tic and environmental variances and heritability were estimated using path models with maximum likelihood estimation techniques. Results: MZ twins were more similar than DZ twins for all clinical measures . Statistically significant genetic variance was found for both the severit y and extent of disease. AP was estimated to have approximately 50% heritab ility, which was unaltered following adjustments for behavioral variables i ncluding smoking. In contrast, while MZ twins were also more similar than D Z twins for gingivitis scores, there was no evidence of heritability for gi ngivitis after behavioral covariates such as utilization of dental care and smoking were incorporated into the analyses. Conclusions: These results confirm previous studies and indicate that appro ximately half of the variance in disease in the population is attributed to genetic variance. The basis for the heritability of periodontitis appears to be biological and not behavioral in nature.