title: Effect of pH on endotoxin affinity for metal-ceramic alloys.
abstract: BACKGROUND
  Crevicular pH may modify bacterial endotoxin affinity for high-noble metal-ceramic alloys.
  
  
  OBJECTIVE
  Porphyromonas gingivalis lipopolysaccharide (LPS) affinity for 3 metal-ceramic alloys at 3 different pH levels was compared in vitro by measuring adsorption to and release from the alloy surface.
  
  
  METHODS
  Metallographically polished disks were fabricated from Pd-Ag-Sn, Au-Pd-Ag-Sn-In, and Au-Pd-In-Ga alloys. Clean disks were placed individually into 1 mL at pH 6.5, 7.0, or 7.5 phosphate-buffered saline solution containing 0.9 endotoxin units per square millimeter tritiated LPS (n = 3 disks per alloy-pH group). The disks were incubated for 24 hours at 37 degrees C before being transferred to LPS-free buffer and incubated, again for 24 hours at 37 degrees C, to evaluate elution. This transfer continued at 24-hour intervals up to 96 hours total elution incubation. Lipopolysaccharide adsorption to and elution from disks was determined through liquid scintillation spectrometry. Adsorption data were evaluated with a 2-way analysis of variance (alpha=.05) and the post hoc Tukey honestly significant difference test.
  
  
  RESULTS
  Lipopolysaccharide adsorption values ranged from 0.48 +/- 0.04 EU/mm(2) for the Au-Pd-Ag-Sn-In alloy at pH 7.5 to 0.75 +/- 0.04 EU/mm(2) for the Pd-Ag-Sn alloy at pH 6.5. Alloy type (P=.0001) and environmental pH (P=.0001) significantly influenced adsorption. Adsorption to the Pd-Ag-Sn and Au-Pd-In-Ga alloys at pH 6.5, 7.0, and 7.5 were similar and decreased with increasing pH. In contrast, adsorption to the Au-Pd-Ag-Sn-In alloy was significantly less than to other alloys at pH 6.5 but did not differ at other pH levels. Lipopolysaccharide release from the alloy surface could not be detected.
  
  
  CONCLUSIONS
  P. gingivalis LPS affinity for metal-ceramic alloys was modified by environmental pH. The degree of LPS adsorption depended on the composition and surface chemistry of each alloy.
authors.affiliation: College of Dentistry, University of Illinois at Chicago, 60612-7212, USA. KentK@uic.edu
authors.forename: K L
authors.initials: KL
authors.lastname: Knoernschild
authors.forename: W L
authors.initials: WL
authors.lastname: Bacon
authors.forename: G S
authors.initials: GS
authors.lastname: Fischman
authors.forename: S D
authors.initials: SD
authors.lastname: Campbell
mesh_terms: D000327:Adsorption; D000704:Analysis of Variance; D003722:Dental Alloys; D003776:Dental Porcelain; D004563:Electrochemistry; D005883:Gingival Crevicular Fluid / Q000737:chemistry; D006047:Gold Alloys; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000737:chemistry*; D016876:Metal Ceramic Alloys; D016966:Porphyromonas gingivalis / Q000737:chemistry / Q000302:isolation & purification; D018709:Statistics, Nonparametric
chemical_list: D003722:Dental Alloys; D006047:Gold Alloys; D008070:Lipopolysaccharides; C096534:Lodestar Gold Ceramic Alloy; D016876:Metal Ceramic Alloys; C080318:Willceram W-I; D003776:Dental Porcelain; C081267:Willceram porcelain