An in vivo evaluation of the biocompatibility of anodic plasma chemical (APC) treatment of titanium with calcium phosphate

Abstract

Implant loosening is an unresolved complication associated with prosthetics. Previous studies report improved osseointegration with hydroxyapatite (HA) or tri-calcium phosphate coatings. Unfortunately, the brittleness and low strength of these coatings in adhesion to the implant or internal cohesion is problematic, restricting their use. Anodic plasma-chemical (APC) treatment, an advanced anodisation method, allows for porous oxide layer formation with incorporation of calcium and phosphate directly into the oxide. This produces superior adhesive strength than a conventional coating of calcium phosphate offering potential for long-term osseointegration. Although the cytocompatibility of several APC treatments have been previously shown, this study was the first to investigate the biocompatibility and osteoconductivity of APC surfaces in vivo when compared with standard HA coated and noncoated commercially pure titanium implant cortical screws. Sample screws were implanted in female Swiss alpine sheep for 12 weeks. Bone remodelling in situ, differences in bone apposition resulting in cortical thickening as well as peak removal torque measurements were assessed. We found no significant differences between the tested coatings and no delamination was observed with any of the APC-treated surfaces. The results suggest that APC-treated samples have similar biological performance to HA-coated screws. In our opinion, APC treatment, which also has superior binding strength to the base metal compared with standard HA coatings as well as similar biocompatibility as shown here, holds great potential for biomedical applications. Now that the in vivo biocompatibility has been proven, the work is being extended to more challenging in vivo models.

Influence of steel implant surface microtopography on soft and hard tissue integration

“…Surface chemistry also influences the initial protein interactions with the surface, but as shown with the XPS results, the surface chemistry was not altered by the roughening processes, with a final electropolishing step neutralising any possible previous step changes [Table (B)]. The results would therefore support that surface microtopography is influencing the body's reaction immediately upon implantation through protein adsorption, cell adhesion (or not) and cell differentiation as previously published, right up to the late tissue reactions, as shown here and in other studies …”

“…The stability and integration of implants with bone also depends upon the nature of the interface . Data regarding bone contact from this study confirmed previous observations implicating a positive correlation between increased surface micro‐roughness and bone attachment (Figures and ) . In contrast to the above mentioned studies where the implants had initial direct bone contact, the present study was not originally designed for this evaluation, but for soft tissue and capsule evaluation upon the upper plate surfaces (Figures and ).…”

“…Surface microroughness has been extensively shown to govern cell and tissue responses in vitro and in vivo and has proven particularly useful for controlling osseointegration where implant stability is essential. [26][27][28] Research defining cpTi as having a micro-rough surface has been particularly fruitful in producing significant clinical improvements for supporting implant stability via osseointegration. In contrast, while EPSS also has a distinguished clinical record, it is produced with a smooth mirror-like finish, normally void of micro-roughness.…”

An in vivo evaluation of surface polishing of TAN intermedullary nails for ease of removal

“…In terms of hard tissue response we have shown that smoother surfaces compared to the clinically available 'standard' micro-rough counterparts hold potential for reducing bony over-growth by essentially reducing osteoblast 'specific' genotypic expression via alterations in the cell shape and cytoskeletal organization (Hayes et al, 2008). We have also observed this effect translated to a tissue level in vivo, where the importance of the surface characteristics of clinically used devices were found to directly control specific tissue outcomes (Welton, 2006;Pearce et al, 2008;Schlegel et al, 2009).…”

Surface engineered titanium alloys for biomedical devices

“…Recently Schlegel et al (2008) used anodic plasma-chemical (APC) treatment to fabricate a porous oxide layer incorporating calcium and phosphate directly in the oxide. This produced superior adhesive strength to a conventional calcium phosphate coating, offering potential for long-term osseointegration.…”