title: An in vitro quantitative antibacterial analysis of amalgam and composite resins.
abstract: OBJECTIVE
  Antibacterial properties of restorative dental materials such as amalgam and composite resins may improve the restorative treatment outcome. This study evaluates the antibacterial properties of three composite resins: Z250, Tetric Ceram, P60 and a dental amalgam in vitro.
  
  
  METHODS
  Streptococcus mutans and Actinomyces viscosus served as test microorganisms. Three quantitative microtiter spectrophotometric assays were used to evaluate the effect of the restorative materials on: (i) early-stage biofilm using a direct contact test (DCT); (ii) planktonic bacterial growth; (iii) bacterial growth in the materials' elute. For comparison purposes, agar diffusion test (ADT) was also performed.
  
  
  RESULTS
  The effect of the composite resins on bacterial growth was minimal and limited to a few days only. One-week-aged composites promoted growth of S. mutans and A. viscosus. The antibacterial properties in direct contact were more potent than in planktonic bacterial growth. Amalgam showed complete inhibition of both bacteria in all phases, and the effect lasted for at least 1 week. The materials' elute had no effect on both bacterial growth with the exception of complete inhibition of S. mutans in amalgam. The later results correlated with the ADT.
  
  
  CONCLUSIONS
  The present findings demonstrate potent and lasting antibacterial properties of amalgam, which are lacking in composite resins. This may explain the clinical observation of biofilm accumulated more on composites compared to amalgams. It follows that the assessment of antibacterial properties of poorly-soluble materials has to employ more than one assay.
authors.affiliation: Department of Prosthodontics, Hebrew University-Hadassah School of Dental Medicine, P.O. Box 12272, Jerusalem 91120, Israel.
authors.forename: Nurit
authors.initials: N
authors.lastname: Beyth
authors.forename: Abraham J
authors.initials: AJ
authors.lastname: Domb
authors.forename: Ervin I
authors.initials: EI
authors.lastname: Weiss
mesh_terms: D016924:Actinomyces viscosus / Q000187:drug effects / Q000254:growth & development; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects; D003188:Composite Resins / Q000494:pharmacology*; D003723:Dental Amalgam / Q000494:pharmacology*; D003764:Dental Materials / Q000494:pharmacology*; D006801:Humans; D005779:Immunodiffusion; D012995:Solubility; D013053:Spectrophotometry; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D003188:Composite Resins; D003764:Dental Materials; C438835:Filtek P60 Composite Resin; C444701:Filtek Z250; C121818:Tetric ceram; D003723:Dental Amalgam