Title: Zirconia-titanium Composite Implant Exhibits Higher Corrosion Resistance Than Titanium Implant
Reema Dhanani (Presenter)
University of Washington
Daniel Chan, University of Washington
Alexander Pozhitkov, University of Washington
Eric Lindahl, University of Washington
Objectives: Titanium corrosion was previously suggested as one of the causes for peri-implantitis. Our group recently developed a composite material, whereby the body of the implant is made of zirconia covered with titanium zones - “stripes” - electrically insulated from one another. The objective of this work is to evaluate the bacteria-mediated corrosion of the new composite compared to a commercial implant.
Biocompatible zirconia screws were pre-treated with heat at 300 oC for 12 hours, cooled down, treated with 15% HF for 20 min, rinsed with water and dried at 100 oC. Ti was deposited onto the screws in a vacuum evaporator (JEOL). After Ti deposition, several bands of a heat-shrink tube were placed onto the coated screws followed by 30s of 15% HF etching followed by water rinse. Uncoated screws and a commercial implant were used as controls.
Bacterial culture medium used composed of Trypticase Soy Broth 30 g/l and Yeast Extract 5 g/l, pH adjusted to 7.2 and autoclaved. Each 1L of medium base was supplemented with Vitamin K3 stock 0.2 ml and Hemin stock 10 ml. Hemin stock was prepared from 50 mg Hemin dissolved in 1 ml 1M NaOH subsequently diluted with 99 ml water. Hemin stock was stored at 4°C. Vitamin K3 stock was prepared by dissolving 250 mg Vitamin K in 50 ml 98% ethanol. The three types of materials were suspended in 50 ml jars and inoculated with oral bacterial, then incubated aerobically for two weeks. The gel closes to the implant were harvested by coring and then digested for analysis. Agar gel was weighted before microwave assisted digestion in nitric acid and instrumental analysis of elements by Inductively coupled plasma mass spectrometry (ICP-MS). The experiment was duplicated after two weeks.
Results: The leached titanium concentration is shown in Table 1. The agar gel medium is in fact a blank for the measurements. Subtracting the concentration, the distribution of concentrations is shown on Figure 1.
Conclusions: Consistent with our previous research, the interruption of the Ti electrical conductivity leads to the decreased Ti leaching due to corrosion. The striped composite implant holds a promise for future optimization, since we already achieved 50% reduction of corrosion.