title: [Analysis of the bacterium adhesions on the surface of PFM materials in vitro].
abstract: OBJECTIVE
  With the observation of bacterial adhesion on the surface of the PFM and enamel, we analyzed the sequence of these adhesions and offer options for prevention of their occurrence.
  
  
  METHODS
  The specimen made of PFM were polished step by step. Then they, along with the enamel were put into the liquid BHI culture medium containing Ua, Pg and An. After 6h, 12h and 24h the adhesive microbial amount in the culture medium was determined by counting formation unit. F test was used to analyze the results with SPSS 6.0 software package.
  
  
  RESULTS
  Pg was found neither on the surface of specimen, nor in the liquid BHI culture medium; The value of Ua/An in the groups of PFM was less than that in the groups of enamel within 6 hours. And 12 hours later, the maximal increment of An was seen in the group of PFM. And there was no change in the groups of PFM and enamel during 12 and 24 hours.
  
  
  CONCLUSIONS
  Pg was inhibited when these bacteria were cultured together. If we wish to prevent the adhesion of Ua and An, the first 12 hours is the critical period for PFM. Given the result of the analysis, PFM is a good restoration.
authors.affiliation: Department of Prosthodontics, Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Key Lab of Stomatology, Shanghai 200011, China. zhaojun161@126.com
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Ren-xiu
authors.initials: RX
authors.lastname: Zhang
authors.forename: Yuan-li
authors.initials: YL
authors.lastname: Zheng
mesh_terms: D001422:Bacterial Adhesion; D003743:Dental Enamel; D066298:In Vitro Techniques; D013499:Surface Properties