Biologic effects of surface roughness and fluorhydroxyapatite coating on osteointegration in external fixation systems: An in vivo experimental study

Abstract

The concomitant influence of surface roughness and fluorhydroxyapatite (FHA) coating of titanium (Ti) implants on bone response was investigated. For this purpose, titanium screw-shaped implants with a lower degree (Y371) and a higher degree (TiPore300) of surface roughness, coated with FHA and uncoated, were transversally inserted into the diaphyses of sheep tibiae for 12 weeks. Four sheep received Y371 (group A) and Y371 + FHA (group B) screws and four sheep received TiPore300 (group C) and TiPore300 + FHA (group D) screws. For each type of material, the morphology and microstructure of implant-facing bone were evaluated. The host bone of each tibia was used as a control. In all groups the bone tissue did not reach a complete maturation. The higher degree of roughness, perhaps due to an excessive irregularity of the surface, induced the worst osteointegration: a fibrous tissue layer between screw and new bone tissue was often present. Nevertheless, as viewed by XRD, no crystallographic change of the apatite lattice was observed in any of the implants. In contrast, the microhardness value, an index of bone mineralization, was higher in the uncoated screws and decreased progressively in the following order: group C > group A > group B > group D. The association of plasma spraying with roughness treatment constitutes a complex system that seems to interfere with bone mineralization. A chemical change of the surface, perhaps with more Ti release or more coating degradation, could be responsible for such impairment. The authors emphasize the necessity for simultaneous evaluation of surface topography and chemistry as well as an improvement in plasma-spraying and post-processing techniques and in standard procedures for materials characterization.

Porous spherical hydroxyapatite and fluorhydroxyapatite granules: processing and characterization

“…Table 3 illustrates Thus, it can be supposed that the minor addition up to 10% of FA to HA does not influence negatively the protein adsorption onto the porous granules, and that the surface morphology is probably more important factor affecting the protein behavior. This is in agreement with the opinion about FHA does not reduce the osteointegration ability of the implanted device [5,14,15]. The addition of fluoride ions can result in a positive consequence due to their influence on the driving force for precipitation of apatite from solution, i.e.…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Presumably, this is due to the lowest solubility, good chemical stability of FA and toxicity of high amounts of fluorides. However, attempts to test FA-containing formulations (Gineste et al 1999;Agathopoulos et al 2003;Yoon et al 2005;Bogdanov et al 2009;Nordquist et al 2011), ion-substituted FA (Kheradmandfard et al 2012;Sharifnabi et al 2014), FHA (Savarino et al 2003;Vitkovič et al 2009) and porous FA bioceramics (Chaari et al 2009) are kept performing. The effect of fluoride contents in FHA on both osteoblast behavior (Qu and Wei 2006;Bhadang et al 2010) and leukemia cells proliferation (Theiszova et al 2008) has been described.…”

Calcium orthophosphates

“…Due to its low solubility, good chemical stability and the toxicity of high amounts of fluorides, chemically pure FA is rarely used as a bone substituting material 442 . However, various FA-containing composites, 443 - 445 FHA 446 , 447 and porous FA bioceramics 448 seem to be better candidates for biomedical applications. Furthermore, due to the ability to form FHA and/or HFA, minor amounts of fluorides might be intentionally added to calcium orthophosphate biomaterials 449 - 455 .…”