Multivariate binary logistic model of association between the number of IgG antibodies to periodontal bacteria and TNF-α and AD. Note: when TNF-α and IgG antibodies against A. actinomycetemcomitans, P. gingivalis and T. forsythia were simultaneously included into the model both variables associated with AD independently. IgG=number of positive IgG antibody tests in the highest quartile. Since age was not significant, it was not included into this model.