title: Antibacterial properties of aged dental cements evaluated by direct-contact and agar diffusion tests.
abstract: BACKGROUND
  Since failure of fixed partial dentures is most frequently caused by caries, it would be advantageous if cements possessed antibacterial properties.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the antibacterial properties of 3 dental cements using the direct-contact test and agar diffusion test.
  
  
  METHODS
  For the direct-contact test, wells (n = 4) of microtiter plates were coated with the tested cements (Harvard cement, Duralon, and Ketac-Cem) while Streptococcus mutans suspension was placed directly on the cements. Bacterial growth was evaluated by a temperature-controlled microplate spectrophotometer. Eight wells of bacteria without the tested cements served as the positive control. Six wells of the tested cement without bacteria served as the negative control. For the agar diffusion test, triplicate specimens of freshly mixed cements were poured into uniform wells (5 mm in diameter) punched in the agar plates inoculated with Streptococcus mutans . After incubation at 37 degrees C for 24 hours, the agar plates were examined for bacterial growth and the diameter of the halo formed in the bacterial lawn was measured. In both tests, each cement was mixed in 2 different powder/liquid ratios. For the direct-contact test, data were initially recorded after 1 hour of incubation. Additional experiments were performed on specimens that were aged for 24 hours, 1 week, 1 month, and 3 months before assessment by either direct-contact test or agar diffusion test. The data were subjected to 1-way ANOVA with the Tukey post hoc test (alpha=.05).
  
  
  RESULTS
  Compared with the control group, Duralon and Harvard cements demonstrated antibacterial properties even after 3 months with the direct-contact test (P <.002), while Ketac-Cem exhibited no antibacterial properties. In the agar diffusion test, no antibacterial activity was observed for any of the tested cements. The different powder/liquid ratios had a negligible effect on the antibacterial properties of the tested cements.
  
  
  CONCLUSIONS
  Within the limitations of this study, Duralon and Harvard cements possessed prolonged antibacterial properties, while Ketac-Cem exhibited no antibacterial activity. The direct-contact test may be a more suitable test than the agar diffusion test to evaluate antibacterial properties of definitive cements.
authors.affiliation: Department of Oral Rehabilitation, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. lewins@post.tau.ac.il
authors.forename: Israel
authors.initials: I
authors.lastname: Lewinstein
authors.forename: Shlomo
authors.initials: S
authors.lastname: Matalon
authors.forename: Shimshon
authors.initials: S
authors.lastname: Slutzkey
authors.forename: Ervin I
authors.initials: EI
authors.lastname: Weiss
mesh_terms: D000362:Agar; D000890:Anti-Infective Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003738:Dental Cements / Q000737:chemistry / Q000494:pharmacology*; D004058:Diffusion; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008277:Magnesium Oxide / Q000737:chemistry; D008422:Materials Testing; D011076:Polycarboxylate Cement / Q000737:chemistry; D013053:Spectrophotometry; D013295:Streptococcus mutans / Q000187:drug effects* / Q000254:growth & development; D013499:Surface Properties; D013997:Time Factors; D015034:Zinc Oxide / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D000890:Anti-Infective Agents; D003738:Dental Cements; D005899:Glass Ionomer Cements; D011076:Polycarboxylate Cement; D008277:Magnesium Oxide; D015036:Zinc Phosphate Cement; C074226:Harvard Cement; C040235:Ketac-cem; D000362:Agar; C041940:Duralon; D015034:Zinc Oxide