IADR Abstract Archives
Surface Degradation of Zirconia in Early-Colonizing Oral Bacteria In Vitro
Objectives: The effect of early-colonizing oral bacterial adhesion on the surface of zirconia (ZrO2) has yet to be fully understood despite their current use in dental implant applications. The goal of this study was to evaluate surface degradation of ZrO2 in terms of physical properties after exposure to early-colonizing oral bacteria.
Methods: Five commercial ZrO2 dental implants (75c-40-10 Zirkolith, Z-Systems) were used. Three implants were immersed in early-colonizing polyculture (5ml) consisting of Streptococcus species: S. mutans, S. sanguinis, and S. salivarius. A positive control implant was immersed in aqueous lactic acid (pH=5) and a negative control in un-inoculated bacterial media (pH=7). Implants were immersed for 30 consecutive days in 5% CO2 atmosphere at 37°C. The optical density (OD600) and pH were measured in addition to replenishing 2ml of media every 48h to ensure viability. Post-immersion, specimens were ultrasonically cleaned, and the surface morphology, chemistry, and phase composition were assessed using optical microscopy (OM), X-ray photoelectron spectroscopy, and Raman spectroscopy, respectively.
Results: No visual signs of surface degradation were observed on any ZrO2 implant post-immersion using OM. Shifts to higher binding energy values of primary constituent elements (Zr3d5/2, O1s) were observed for bacteria-immersed specimens (183.0±0.3eV, 530.7±0.2eV) and positive control (182.8±0.1eV, 530.5±0.1eV) as compared to negative control (182.2±0.2eV, 530.1±0.2eV). Deposition of carbon- and nitrogen-containing compounds was prevalent on bacteria-immersed implants as compared to positive and negative controls despite ultrasonication cleaning. Raman analysis revealed the presence of 1-10% of monoclinic phase content on the rough implant screw surface of bacteria-immersed and positive control implants but only tetragonal phase was found on the implant collar or any region of the negative control.
Conclusions: Early-colonizing Streptococcus species can accelerate tetragonal-to-monoclinic phase transformation of dental ZrO2 surfaces through the production of lactic acid. The rough implant screw seems to be more prone to phase transformation than the machined implant collar.
Methods: Five commercial ZrO2 dental implants (75c-40-10 Zirkolith, Z-Systems) were used. Three implants were immersed in early-colonizing polyculture (5ml) consisting of Streptococcus species: S. mutans, S. sanguinis, and S. salivarius. A positive control implant was immersed in aqueous lactic acid (pH=5) and a negative control in un-inoculated bacterial media (pH=7). Implants were immersed for 30 consecutive days in 5% CO2 atmosphere at 37°C. The optical density (OD600) and pH were measured in addition to replenishing 2ml of media every 48h to ensure viability. Post-immersion, specimens were ultrasonically cleaned, and the surface morphology, chemistry, and phase composition were assessed using optical microscopy (OM), X-ray photoelectron spectroscopy, and Raman spectroscopy, respectively.
Results: No visual signs of surface degradation were observed on any ZrO2 implant post-immersion using OM. Shifts to higher binding energy values of primary constituent elements (Zr3d5/2, O1s) were observed for bacteria-immersed specimens (183.0±0.3eV, 530.7±0.2eV) and positive control (182.8±0.1eV, 530.5±0.1eV) as compared to negative control (182.2±0.2eV, 530.1±0.2eV). Deposition of carbon- and nitrogen-containing compounds was prevalent on bacteria-immersed implants as compared to positive and negative controls despite ultrasonication cleaning. Raman analysis revealed the presence of 1-10% of monoclinic phase content on the rough implant screw surface of bacteria-immersed and positive control implants but only tetragonal phase was found on the implant collar or any region of the negative control.
Conclusions: Early-colonizing Streptococcus species can accelerate tetragonal-to-monoclinic phase transformation of dental ZrO2 surfaces through the production of lactic acid. The rough implant screw seems to be more prone to phase transformation than the machined implant collar.