Table 1.
Mechanical, physical and chemical methods used for surface modification of Ti implants for cranial and maxilofacial surgery.
| Mechanical Methods | ||
| Technologies | Texture/Roughness Size | Outcome/Reference |
| Machining Grinding Blasting |
~1 μm, rough surface formed by subtraction process | Specific surface topographies. Improved adhesion and bonding. Auxiliary method to remove contamination. Rarely solely used [25,26,27,28,29,30,31,32] |
| Shoot peening | 20–80 nm grains on the surface | Improved fatigue resistance, hardness and wear [33,34] |
| Friction stir processing (FSP) | <1 μm, ultrafine grained surface | Improved sliding friction and wear resistance. Incorporation of AgNPs, Zn with antibacterial effect [34,35] |
| Attrition | <100 nm grains on the surface | Improved tensile properties and surface hardness, higher hydrophilicity, better biological affinity [24,36,37] |
| Hydrothermal & pressure (HPT) |
flake-like titanate layer on Ti substrate, pore size of 300–600 nm | Minimize the time-consumption and the manufacturing cost. Enhance the in vitro cell-material interactions [38] |
| Physical Methods | ||
| Technologies | Texture/Roughness Size | Outcome/Reference |
| Thermal (flame or plasma) spraying | ~30 to ~200 μm of coatings, such as TiO2, HA, CaP, Al2O3, ZrO2, TiO2 | Improved wear/corrosion resistance and biocompatibility [24,39,40,41] |
| Physical vapor deposition: evaporation, sputtering, ion plating | <1 μm, TiN, TiC, TiCN, TiO2, amorphous carbon films, full density | Improved wear/corrosion resistance and blood compatibility [34,36,42,43] |
| Ion implantation and deposition | ~10 nm of surface modified layer and/or thin film such | Improved hardness, wear, fatigue/corrosion resistance |
| as Ti–O, Ti–N films | and blood compatibility [44,45] | |
| Plasma treatment | <100 nm, TiO2, TiN, TiOH, TiCN layers, full density | Clean and sterilize surface, remove native oxide layer. Improved hardness, wear and corrosion resistances, fatigue limit and biocompatibility [46,47] |
| Plasma polymerization | Not reported | Bioactive surface. Improved cell adhesion [48] |
| Chemical Methods | ||
| Technologies | Texture/Roughness Size | Outcome/Reference |
| Acidic treatment (HF, HCl, H2SO4) |
~10 nm oxide layer on the surface | Remove oxide scales and contamination. Used in combination with other treatments (blasting), higher roughness promoting osteoblasts attachment [49,50] |
| Alkali treatment (NaOH, KOH) | ~1 μm sodium titanate gel on the surface | Improved biocompatibility, bioactivity or bone conductivity [32,51] |
| Hydrogen peroxide treatment |
Inner oxide layer <10 nm; outer porous oxide layer up to 40 nm | Improved biocompatibility or bioactivity [34,52] |
| Passivation treatment (nitric acid, phosphoric acid) |
~2–30 nm oxide layer dominated by TiO2, uniform, full density | Enhanced corrosion, resistance and wear resistance, better bioactivity compared to mechanical treatment [34,53] |
| Electrochemical methods (anodization, electrodeposition) | ~10 nm–10 μm uniform, controllable thickness of TiO2 layer; adsorption and incorporation of electrolyte anions | Improved adhesive bonding, corrosion resistance, bioactivity, specific surface topographies [54,55] |
| Chemical vapor deposition | ~1 μm of TiN, TiC, TiCN, diamond and diamond-like carbon thin film, nearly full density | Extremely high hardness and wear resistance compared with Ti substrate. Improved corrosion resistance and blood compatibility [56,57] |
| Sol-gel | <10 μm of thin ceramic coatings, such as Ca3(PO4)2, TiO2, SiO2 | Highly homogeneity and improvement in bioactivity [58,59] |
| Biochemical methods (by soaking- peptide, proteins immobilization, functional molecules, drug loaded) | self-assembled monolayers, does not ensure controlled deposition | Improved bioactivity, biocompatibility, and/or antibacterial functions [60,61] |