Initial in vitro bacterial adhesion on dental restorative materials

Abstract

Objectives: The purpose of this study was to evaluate initial bacterial adhesion on several restorative materials with similar roughness.

Materials and methods: Sixty cylindrical slabs were prepared from four restorative materials: zirconia (Zr), alumina-toughened zirconia (Al-Zr), type III gold alloy (Au), and cp-titanium (Ti). All the materials were polished until a mirror-like shine was achieved. The average surface roughness and topography were determined by atomic force microscopy. Contact angles were measured to calculate surface free energy by the sessile drop technique. After the formation of a salivary pellicle, S. sanguinis, S. gordonii, and S. oralis were inoculated onto the specimens and incubated for 4 h. Quantification of the adherent bacteria was performed by crystal violet staining technique and resazurin reduction assay. One-way ANOVA and Tukey's post hoc test were adopted for statistical analysis. The level of significance was 0.05.

Results: The Ra values determined with atomic force microscopy for all specimens were lower than 5 nm. Surface free energy increased in the order of Al-Zr, Zr, Ti, and Au. Differences were significant between the investigated materials in both crystal violet absorbance and fluorescence intensities. Gold alloy showed the highest values for all bacterial strains (p<0.05).

Conclusions: Zirconia, alumina-toughened zirconia, and titanium may be more suitable than gold alloy as an abutment material with respect to the initial bacterial adhesion and subsequent advance of peri-implantitis.