Bacterial Colonization of Zirconia Ceramic Surfaces: An In Vitro and In Vivo Study

Purpose: The microbial colonization of new ceramic materials developed for abutment manufacturing was assessed. Materials and Methods: The materials used in these experiments were disks of "asfired" and "rectified" ceramic material made of tetragonal zirconia polycrystals stabilized with yttrium (Y-TZP) and commercially pure grade 2 titanium (Ti) with corresponding eluates. They were tested in vitro with the following bacteria: Streptococcus mutans, S sanguis, Actinomyces viscosus, A naeslundii, and Porphyromonas gingivalis. Proliferation was evaluated on plates by inhibitory halos around pits, previously inoculated with eluates obtained from the materials. Bacterial adhesion on materials was quantified by spectrophotometric evaluation of the slime production by the same bacteria. Moreover, early bacterial adhesion was evaluated in human volunteers and observed with SEM. Results: No inhibition of bacterial proliferation using eluates was observed. In vitro as-fired and rectified Y-TZP showed significantly more adherent S mutans than did Ti disks, while S sanguis seemed to adhere easily to Ti specimens. No differences were noted for Actinomyces spp and P gingivalis. In vivo Y-TZP accumulated fewer bacteria than Ti in terms of the total number of bacteria and presence of potential putative pathogens such as rods. No differences were observed between rectified and as-fired Y-TZP. Discussion: Overall, Y-TZP accumulates fewer bacteria than Ti. Conclusion: Y-TZP may be considered as a promising material for abutment manufacturing.