Evidence of a substantial genetic basis for risk of adult periodontitis.
BACKGROUND
A few previous studies have suggested that risk for adult periodontitis (AP) has a genetic (heritable) component. We estimated genetic and environmental variances and heritability for gingivitis and adult periodontitis 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), attachment loss (AL), plaque, and gingivitis (GI) were assessed on all teeth by two examiners. Measurements were averaged over all sites, teeth, and examiners. Extent of disease in subjects was defined at four thresholds: the percentage of teeth with AL > or = 2, AL > or = 3, PD > or = 4, or PD > or = 5 mm. Genetic 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 severity and extent of disease. AP was estimated to have approximately 50% heritability, which was unaltered following adjustments for behavioral variables including smoking. In contrast, while MZ twins were also more similar than DZ twins for gingivitis scores, there was no evidence of heritability for gingivitis 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 approximately 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.
Michalowicz
B S
BS
Department of Preventive Sciences, University of Minnesota School of Dentistry, Minneapolis, USA.
Diehl
S R
SR
Gunsolley
J C
JC
Sparks
B S
BS
Brooks
C N
CN
Koertge
T E
TE
Califano
J V
JV
Burmeister
J A
JA
Schenkein
H A
HA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D003729:Dental Care / Q000706:statistics & numerical data; D003774:Dental Plaque Index; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D014644:Genetic Variation; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010512:Periodontal Index; D010518:Periodontitis / Q000235:genetics*; D012307:Risk Factors; D012907:Smoking