Adhesion of Streptococcus mutans on highly translucent zirconia: Influence of surface properties and polyelectrolyte multilayer coatings.

Statement Of Problem: Low-pressure airborne-particle abrasion has been used to improve the adhesion of zirconia to resin cement. However, whether a polyelectrolyte multilayer can be used to reduce bacterial adhesion to abraded zirconia is unclear.

Purpose: The purpose of this in vitro study was to evaluate whether polyelectrolyte multilayers added to airborne-particle abraded zirconia can minimize biofilm development.

Material And Methods: Commercially available zirconia powders with yttria content between 3 and 5 mol% were isostatically pressed into Ø20-mm disks and sintered at 1450 °C for 2 hours (n=8). Untreated specimens were compared with airborne-particle abraded ones. Specimens with 3 mol% yttria were further coated with polyelectrolyte multilayers (n=4). The surfaces were characterized by measuring the roughness, hydrophobicity, and surface charge using profilometry, atomic force microscopy, tensiometry, and electrokinetic analyzer, respectively. The extent of bacterial adhesion was determined using spectrophotometry and scanning electron microscopy. Data were analyzed with a single-factor ANOVA and F-test for variance (α=.05).

Results: The airborne-particle abrasion of zirconia increased the surface roughness, which led to the pronounced adhesion of Streptococcus mutans. However, polyelectrolyte multilayer coatings made of chitosan and pol(yacrylic acid) reduced the extent of bacterial adhesion, especially in as-sintered specimens, with 70% fewer adhered bacteria than airborne-particle abraded specimens. The effect of polyelectrolyte multilayer coating on the airborne-particle abraded series was greatest with the poly(acrylic acid)-terminating specimens, with 50% fewer adhered bacteria than the uncoated ones.

Conclusions: Airborne-particle abraded zirconia specimens coated with biocompatible polyelectrolyte multilayer coatings with a negatively charged terminating layer were associated with a 50% reduction in bacteria adhesion compared with uncoated specimens.