Nanoparticles and Nanostructured Surface Fabrication for Innovative Cranial and Maxillofacial Surgery

Abstract

A novel strategy to improve the success of soft and hard tissue integration of titanium implants is the use of nanoparticles coatings made from basically any type of biocompatible substance, which can advantageously enhance the properties of the material, as compared to its similar bulk material. So, most of the physical methods approaches involve the compaction of nanoparticles versus micron-level particles to yield surfaces with nanoscale grain boundaries, simultaneously preserving the chemistry of the surface among different topographies. At the same time, nanoparticles have been known as one of the most effective antibacterial agents and can be used as effective growth inhibitors of various microorganisms as an alternative to antibiotics. In this paper, based on literature research, we present a comprehensive review of the mechanical, physical, and chemical methods for creating nano-structured titanium surfaces along with the main nanoparticles used for the surface modification of titanium implants, the fabrication methods, their main features, and the purpose of use. We also present two patented solutions which involve nanoparticles to be used in cranioplasty, i.e., a cranial endoprosthesis with a sliding system to repair the traumatic defects of the skull, and a cranial implant based on titanium mesh with osteointegrating structures and functional nanoparticles. The main outcomes of the patented solutions are: (a) a novel geometry of the implant that allow both flexible adaptation of the implant to the specific anatomy of the patient and the promotion of regeneration of the bone tissue; (b) porous structure and favorable geometry for the absorption of impregnated active substances and cells proliferation; (c) the new implant model fit 100% on the structure of the cranial defect without inducing mechanical stress; (d) allows all kinds of radiological examinations and rapid osteointegration, along with the patient recover in a shorter time.

Keywords: endoprosthesis; patented solutions; titanium cranioplasty.

Figure 1

Intraoperatively, surgical details of titanium cranioplasty procedure in the case of a large defect (from private collection of Assoc. Prof. Aurel Mohan).

Figure 2

Surface properties of Ti mesh for cranioplasty evidenced by different microscopic techniques: (a) light microscopy image in phase contrast, longitudinal section, 500×, Kroll reagent; (b) Scanning Electron Microscopy 2000×; (c,d) 3D and 2D Atomic Force Microscopy images; (e) contact angle investigation on the surface of the titanium mesh.

Figure 3

The main sequence of events occurring in vivo, during interaction between Ti surface and biological environment.

Figure 4

(a) The flow chart of SeNPs production via hydrothermal reaction using different saccharides as reducing agent; (b) TEM image of SeNPs used for the surface modifications of Ti mesh for cranioplasty, along with the surface morphology of the coating upon in situ SeNPs deposition and details of fibroblasts adhesion on the nanostructured Ti surface.

Figure 5

Left panel- Components of the cranial endoprosthesis with sliding system: Upper sliding layer ①; lower sliding layer ②; fixing system ③. The sliding layers ① and ② are composed of multiple mobile cells with sliding system ④; Positioning of the stent in relation to a schematic model of the cranial box ⑤; Conjugate sliding system ⑥. Right panel-The assembly of the mobile cells to obtain constructive anatomical curvature in order to facilitate customization.

Figure 6

The components of the modular system. Left panel-stratified basal cells, the rigid and flexible connectors. Right panel-the arrangement of modular cells in alternately configuration, so that all rigid connecting bridges align in the S₁ direction, while the flexible ones align in the S₂ direction.

Figure 7

Interconnected layers of the modular system. Left panel-The fixed layer ① is assembled with the movable layer ② so that translations can be performed in the Ox and Oy directions, while maintaining the position of the layer ①. Right panel-The component elements of the cranial prosthesis presented in isometric view, consisting of four basal cells defined in two constructive forms ③, the rigid connecting bridge ④ and the flexible connecting bridge ⑤.