An experimental technique is described to determine contact angles on bacterial layers deposited on cellulose triacetate filters. Measurements with water, water-n-propanol mixtures, and a-bromonaphthalene were employed to calculate surface free energies of various oral bacteria. Differences of 30 to 40 erg cm-2 were obtained for four different bacterial species isolated from the human oral cavity, if the concept of dispersion and polar surface free energies is applied. The free energies obtained were used to calculate interfacial free energies of adhesion of these bacteria from saliva onto tooth surfaces. Bacterial adhesion is energetically unfavorable, if the enamel surface free energy is less than 50 erg cm

No abstract

The higher proportion of caries-associated bacteria on restored tissue indicates that the ecology on the surface of primary lesions differs from that on lesions next to composite, and that secondary caries next to composite may differ from the primary caries process.

The influence of surface free energy on supra‐ and subgingival plaque microbiology was examined in 9 patients with functional fixed prostheses supported by endosseous titanium implants. Two abutments (trans‐mucosal part of the 2 stage implant) were replaced by either a new titanium abutment or a fluor‐ethylene‐propylene (FEP) coated abutment per subject. After 3 months of habitual oral hygiene, plaque samples were taken. Supragingival plaque was examined by means of differential phase‐contrast microscopy, whereas for the subgingivial plaque additional analyses (DNA probes analysis, culturing) were performed. The subgingival samples were taken by paper‐points and by scraping of the subgingival abutment surface. Differential phase‐contrast microscopy showed a significant difference in plaque composition, especially when supragingival plaque was considered (P = 0.05). FEP coated abutments frequently harbored more coccoid microorganisms, whereas spirochetes or motile organisms were only detected around titanium abutments. Subgingivally, the number of colony forming units (CFU) in paper‐points was comparable for both types of abutments. If the to‐the‐abutmentadhering plaque was considered, the number of CFU was 5 times higher on the titanium abutments than on the FEP coated abutments. However, this difference did not reach a statistical level of significance (P = 0.38). The DNA probe analysis of the subgingival plaque collected with paper‐points showed a slightly higher frequency and concentration of perio‐pathogens around 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 lowering the surface‐free energy of intra‐oral hard surfaces results in a reduction in bacterial colonization and in a retardation in its maturation in the supragingival area. For the subgingival area, the influence of this surface characteristic is not as obvious. J Periodontol 1994; 65:162–167.