Bone bonding behavior of titanium and its alloys when coated with titanium oxide (TiO2) and titanium silicate (Ti5Si3)

Abstract

It has been proposed that the essential requirement for artificial materials to bond to living bone is the formation of bonelike apatite on their surfaces in the body. Recent studies have shown that titanium hydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide and titanium silicate on the bonding of titanium alloys to bone was studied. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure load for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological examination by Giemsa surface staining, CMR, and SEM-EPMA revealed the coated titanium alloy implants directly bonded to bone tissue during early implantation. A Ca-P layer was observed at the interface of the coated implants and the bone. The results of this study indicated that TiO2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titanium alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation.

Tensile bond between bone and titanium: A reappraisal of osseointegration

“…Similarly to the difference between silica glass and silica gel, cp titanium and titania gel differ in the density and availability of OH--groups. The gels are readily hydrolyzed and dissolve faster, leaving more OH--groups on its surface (Li et al 1994, Kitsugi et al 1996.…”

“…A sufficient number of OH'-groups are thought to be required to trigger nucleation of hydroxyapatite (Kitsugi et al 1996). With the heat treatment, we intended to obtain a stabilized titania, which is regarded as an inducer for early hydroxyapatite formation.…”

“…In vivo, a titanium surface may become modified to a titania gel by oxidation. An oxide layer on the surface of the titanium implant grows slowly and a titania hydrogel is formed on the surface of the passive layer , Kitsugi et al 1996. Titania gel has many properties in common with, e.g., a silica gel, which forms on bioactive glass and is known to induce epitaxial growth of hydroxyapatite (Bagambisa et al 1993, Li et al 1994.…”

“…The few tensile tests with titanium implants that have been reported do, indeed, show tensile strength of the titanium to bone interface, indicating a chemical bond. This tensile strength developed only after months in vivo (Steinmann et al 1986, Takatsuka et al 1995, Kitsugi et al 1996.…”

Formation of Titania Submicron-Scale Rod Arrays on Titanium Substrate and In Vitro Biocompatibility

“…Note that essential for such tissue-implant bonding is the in vivo apatite-forming ability of implant materials [1][2][3][4]. Chemical treatments of titanium substrates proposed so far [1][2][3][4][5][6][7][8][9][10][11] primarily aimed at controlling the formation of titania [2-101 or titanates [ 1,11 ] on the titanium substrate surfaces that induced apatite formation when those substrates were soaked in a simulated body fluid (SBF of the Kokubo's recipe[121). SBF was similar in inorganic ion composition to human blood plasma.…”