The similarity of periodontal microorganisms between husband and wife cohabitants. Association or transmission?

Fourteen married couples were studied to determine the degree of similarity of the periodontal subgingival flora between paired contralateral sites and between couples. Six sites per person were sampled by a subgingival lavage technique and 10 darkfield morphotypes enumerated at each site. Cross-arch matching revealed a positive association for the presence of medium spirochetes, filaments, large motile rods and cocci (P less than 0.05). The odds that medium spirochetes will be detected at a subgingival site are elevated 7-fold, if present at the contralateral site. Similarly, the odds ratio for filaments was 4.0, 1.3 for large motile rods and 1.6 for cocci. Analysis of data, pairing between couples, revealed a positive association for medium spirochetes and filaments (P less than 0.05). No significant associations were found for randomized pairs of couples using matched sites as controls. The odds of medium spirochetes being present in a patient are 3 times greater if the morphotype is present in the spouse and 30% greater for filaments. Although an individual is "at risk" if these morphotypes are present in the spouse, analyses failed to demonstrate that the presence of any morphotype depends upon, or requires the presence of, that morphotype in the spouse.