Retention of oral microorganisms on cobalt-chromium alloy and dental acrylic resin with different surface finishes

Statement of problem. The effect of surface finish of dental materials on the subsequent contamination by microorganisms. Purpose. This study compared the retention of Streptococcus oralis, Actinomyces viscosus, and Candida albicans on polished, sandblasted (fine and coarse) and electrobrightened cobalt-chromium alloy and dental acrylic resin to assess in vitro the effect of such techniques on prosthesis contamination. Material and methods. Standardized cell suspensions were incubated with test materials for 1 hour at 37 degrees C, after which retained cells were counted by using image analysis (percentage area of a microscopic held covered by cells). Results. Retention of bacterial cells was substantial (S ornlis 12% to 20% and A viscosus 9% to 16%) irrespective of surface finish. Maximal retention was observed on cobalt-chromium alloy that had undergone fine sandblasting and electrobrightening (P<.01). For C albicans, an increase in surface roughness (0.15 to 3.53 mu m) resulted in an increase in retention (3% to 9%). Conclusion. Cell size and the type of roughening significantly affected the retention of microorganisms on surfaces. Electrobrightening of cobalt-chromium alloy did not reduce the surface roughness or subsequent cell attachment.