Controlling for the contributions of smoking or diabetes to periodontal bone loss, estimated odds ratios for predicting lower levels of alveolar bone loss, associated with a greater degree of periodontal health, were strongest when defined by the concurrent presence of a homozygous urokinase plasminogen activator genotype and the nuclease-sensitive plasminogen activator inhibitor type 1 (HindIII) allele (odds ratio = 2.6; 95% confidence interval: 5.8-1.3).