THE INFLUENCE OF SURFACE-FREE ENERGY ON SUPRAGINGIVAL AND SUBGINGIVALPLAQUE MICROBIOLOGY - AN IN-VIVO STUDY ON IMPLANTS

THE INFLUENCE OF SURFACE FREE ENERGY on supra- and subgingival plaque microbiology was examined in 9 patients with functional fixed prosthes es supported by endosseous titanium implants. Two abutments (trans-muc osal part of the 2 stage implant) were replaced by either a new titani um abutment or a fluor-ethylene-propylene (FEP) coated abutment per su bject. After 3 months of habitual oral hygiene, plaque samples were ta ken. Supragingival plaque was examined by means of differential phase- contrast microscopy, whereas for the subgingivial plaque additional an alyses (DNA probes analysis, culturing) were performed. The subgingiva l samples were taken by paper-points and by scraping of the subgingiva l abutment surface. Differential phase-contrast microscopy showed a si gnificant difference in plaque composition, especially when supragingi val plaque was considered (P = 0.05). FEP coated abutments frequently harbored more coccoid microorganisms, whereas spirochetes or motile or ganisms were only detected around titanium abutments. Subgingivally, t he number of colony forming units (CFU) in paper-points was comparable for both types of abutments. If the to-the-abutment-adhering plaque w as considered, the number of CFU was 5 times higher on the titanium ab utments than on the FEP coated abutments. However, this difference did not reach a statistical level of significance (P = 0.38). The DNA pro be analysis of the subgingival plaque collected with paper-points show ed a slightly higher frequency and concentration of perio-pathogens ar ound the titanium abutments. However, the inter-substratum differences were smaller than the inter-subject differences. The latter seemed to be related to patient's dental status. These results indicate that lo wering the surface-free energy of intra-oral hard surfaces results in a reduction in bacterial colonization and in a retardation in its matu ration in the supragingival area. For the subgingival area, the influe nce of this surface characteristic is not as obvious.