Bone-bonding behavior of plasma-sprayed coatings of BioglassR, AW-glass ceramic, and tricalcium phosphate on titanium alloy

Abstract

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Titanium alloy (Ti-6A1-4V) coated with BioglassR (45S5), apatite-wollastonite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP) was prepared, and rectangular specimens were implanted into the tibial bones of mature male rabbits, which were sacrificed 8 or 24 weeks after implantation. The tibiae containing the implants were dissected out and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, contact microradiography, and scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Eight weeks after implantation, the failure loads for implants coated with BioglassR, AW, and TCP were 1.04 +/- 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 weeks after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coated implants did not increase significantly with time. After the detachment test, breakage of the coating layer was observed. Bioactive ceramics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioactive ceramics was lower than that of bulk AW or TCP. It appears impossible to obtain a higher failure load using a bioactive-ceramic coating on titanium alloy. Histologically, the coating layer was found to become detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident. A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the BioglassR coating. For clinical application, it would seem better to use coated metal implants for short-term implantation. However, there is a possibility of breakage of the coating layer because of both dissolution of the bioactive ceramic and mechanical weakness at the interface between the coating layer and the metal implant.

Bioactivity of Titanium Surface Nanostructures Following Chemical Processing and Heat Treatment

“…Apatite formation on the surface of the material is considered a prerequisite for direct bone-bonding. Details of the mechanism underling apatite formation on the surface of alkali-and heat-treated titanium metals have been described by Kim et al 7) Osteogenic cells may attach to the surface of alkali-and heat-treated titanium alloy implant themselves or to the apatite formed on the surface, and this may enhance growth and differentiation [27][28][29][30][31] . Thus, the gap initially created between the bone and the implant following the implantation procedure may be filled with new bone faster with alkali-and heat-treated implants than with untreated implants.…”

Application of .ALPHA.-tricalcium phosphate coatings on titanium subperiosteal orthodontic implants reduces the time for absolute anchorage: a study using rabbit femora

“…A hook was constructed on the center of each disc, using a 0.76 mm-diameter piece of titanium wire that was bent into a loop and welded in place. The bone-contacting surfaces of the implants were coated with α-TCP using the plasma spray method [2][3][4][5][6][7][8][9] . The HA coating was created by hydrothermally processing the α-TCP-coated surface (procedure performed by Advance, Tokyo, Japan).…”

Graded Coatings for Metallic Implant Alloys

“…Several groups have attempted to coat metallic implants with bioactive glasses using enameling, rapid immersion in molten glass, or plasma-spraying techniques. [10][11][12][13] Although some coatings with excellent in vitro behavior have been obtained, most of the glass coatings are marred by cracking and poor reliability at the glass/metal interface. 10,12 In many cases glass/metal reactions lead to the formation of brittle interfacial layers and gas bubbles in the coating.…”

“…[10][11][12][13] Although some coatings with excellent in vitro behavior have been obtained, most of the glass coatings are marred by cracking and poor reliability at the glass/metal interface. 10,12 In many cases glass/metal reactions lead to the formation of brittle interfacial layers and gas bubbles in the coating. 14,15 It has been suggested that future progress in biomaterials must include the development of coatings with programmed dissolution of multilayer surfaces.…”