Multi-Scale Surface Treatments of Titanium Implants for Rapid Osseointegration: A Review

Abstract

The propose of this review was to summarize the advances in multi-scale surface technology of titanium implants to accelerate the osseointegration process. The several multi-scaled methods used for improving wettability, roughness, and bioactivity of implant surfaces are reviewed. In addition, macro-scale methods (e.g., 3D printing (3DP) and laser surface texturing (LST)), micro-scale (e.g., grit-blasting, acid-etching, and Sand-blasted, Large-grit, and Acid-etching (SLA)) and nano-scale methods (e.g., plasma-spraying and anodization) are also discussed, and these surfaces are known to have favorable properties in clinical applications. Functionalized coatings with organic and non-organic loadings suggest good prospects for the future of modern biotechnology. Nevertheless, because of high cost and low clinical validation, these partial coatings have not been commercially available so far. A large number of in vitro and in vivo investigations are necessary in order to obtain in-depth exploration about the efficiency of functional implant surfaces. The prospective titanium implants should possess the optimum chemistry, bionic characteristics, and standardized modern topographies to achieve rapid osseointegration.

Keywords: macro-scale; micro-scale; nano-scale; rapid bone integration; roughness; surface modification.

Figure 1

Structure of skeleton: descending hierarchical macro- to nano-scale structures of natural bone. (Reproduced with permission from [62]. Copyright Elsevier, 2016).

Figure 2

(a) Schematics of a laser beam melting (LBM) machine; (b–d) porous structures; (e–f) micro-CT images of human cancellous bones; (g) stacked hollow cubes; (h–i) the surgical template in pre-blasting and after blasting condition; (j) the dental restorations; (k) a personalized femoral component. (Reproduced with permission from [93]. Copyright Elsevier, 2019).

Figure 3

(a) XTT (Dimethoxazole yellow) results of cell viability of MC3T3-E1 fibroblast cells after 24 h in contact with the extracts in the as-received and laser textured surface; (b,c) SEM of the surface of linear geometry and dimple geometry; (d–f) fluorescent micrographs of the as-received, line geometry and dimple geometry showing the attachment of MC3T3-E1 cells. (Reproduced with permission from [126]. Copyright Elsevier, 2015).

Figure 4

(a) Standard version (grit-blasting); (b) HA coating on standard version; (c) straight Alloclassic™ THA in a 57-year-old female patient for nonunion of a fracture of the femoral neck after removing fixation hardware: immediate postoperative control; (d) radiographic result after 23 years and 3 months of follow-up at the age of 80 years old and 5 months. (Reproduced with permission from [145]. Copyright Elsevier, 2014).

Figure 5

Typical dental implant surface morphology using acid-etching. (Reproduced with permission from [161]. Copyright Elsevier, 2013).

Figure 6

(a) Representative histological images of 3D, 3DA, and SLA implants after implantation for 3 and 6 weeks, respectively (scale bar = 200 μm); (b) quantification of BIC percentages on implant surfaces; (c) SEM of 3D, 3DA, and SLA surfaces; (d) cell morphology on the 3DA surface after culturing of bone marrow stromal cells (BMSCs) for 24 h observed using SEM. (Reproduced with permission from [167]. Copyright Elsevier, 2020).

Figure 7

(a) Schematics during laser engineered net shaping (LENS^TM) and plasma-spraying treatments; (b) bond strength between HA and HA/LENS coatings and substrates; (c) accumulative Ag⁺ release in MgO-Ag₂O-HA/Ti-6Al-4V and MgO-Ag₂O-HA/LENS/Ti-6Al-4V group. (Reproduced with permission from [194]. Copyright Elsevier, 2019).

Figure 8

(a) Schematics during anodization; (b) FESEM micrographs showing the morphology of the highly ordered TiO₂ nanotubes present on NT-Ca/P; (c) high resolution XPS spectra of deconvoluted Ca 2p; (d) potentiodynamic polarization curves of Ti, NT, NT-Ca/P, and NT-RP-Ca/P samples immersed at 37 °C; (e) FESEM micrographs of MG-63 cells cultured on NT-RP-Ca/P surfaces after one day of incubation. (Reproduced with permission from [198]. Copyright Elsevier, 2016).