Experimental evidence for interfacial biochemical bonding in osseointegrated titanium implants.

OBJECTIVES: (i) To identify and quantify an interfacial biochemical bond and the bonding strength of osseointegrated implants with bioactive titanium oxide chemistry, ATiO(x)B (A, metal cations; TiO(x) , titanium oxides/hydroxides; B, non-metal anions) and (ii) to provide quantitative evidence for the biochemical bond theory of osseointegration proposed by Sul et al. for description and explanation of why and how the implants with ATiO(x) B surface oxide chemistry may exhibit a significantly stronger bone response, in spite of the fact that the roughness values approached zero, or were equivalent to or significantly lower than those of the control implants. MATERIALS AND METHODS: We applied a newly developed biochemical bond measurement (BBM) method to model implant surfaces that were "perfectly" smooth nanotopography near-zero roughness as the constant parameter, and used the bioactive surface chemistry of titanium oxide, ATiOx B chemistry as a variable parameter in rabbit tibiae for 10 weeks. In this manner, we determined an interfacial biochemical bond and quantified its bonding strength. RESULTS: The increase in biochemical bond strengths of the test implant relative to the control implant was determined to be 0.018 (±0.008) MPa (0.031 vs 0.021 MPa, n = 10) for tensile strength and 8.9 (±6.1) Ncm (33.0 vs 24.1 Ncm, n = 10) for removal torque. Tensile and removal torque show strong correlation in the Pearson test (r = 0.901, P ≤ 0.001). In addition, histomorphometric measurements including bone-to-metal-contact (BMC, P = 0.007), bone area and newly formed bone showed significant increases in the mean values for ATiO(x) B chemistry (P = 0.007, n = 10). Biochemical bond theory states that the surface oxide chemistry, ATiO(x) B must have more electrical and chemical molecular polarity that fractionally charges the surfaces denoted as δ(+) and δ(-) and leads to electrostatic and electrodynamic interactions with the bone healing cascade, eventually leading to the formation of biochemical bonding at the bone/implant interface. CONCLUSIONS: The present study has provided quantitative evidence for biochemical bond theory of osseointegration of implants with bioactive surface oxide chemistry, ATiO(x) B. The theory of biochemical bonds may provide a scientific rationale pertinent to recent emerging trends and technologies for surface chemistry modifications of implants.