Table 10.

Surface treatments for titanium and its alloys via coating application.

Type	Basis	Substance/Molecule	Reference
By means of physical modification techniques
Bacteriostats	The surface of titanium is modified by altering its TiO2 surface layer via oxidation or mechanical modification (roughness or texture) to electrostatically repel possible bacteria. Polyethylene Glycol (PEG) hydrogels and highly negatively charged or hydrophobic-modified polymers can be used to perform this treatment.	PLL-g-PEG-RGD macromolecule: RGD peptide + (poly (l-lysine) PLL) + polysaccharide + (poly (ethylene glycol) PEG)	[212, 213, 214]
		Polysaccharides such as hyaluronic acid and chitosan	[214, 215, 216, 217, 218]
		Antimicrobial Peptides (AMPs)	[218]
		Chitosan and alginates	[219]
		Environmentally-sensitive (smart) polymers: Poly (N-isopropylacrylamide: polyNIPAM)	[220, 221, 222]
Bactericides	They make it possible to kill bacteria using various mechanisms, such as disruption of the bacterial membrane (destruction or synthesis inhibition), prevention of cellular respiration, blocking of DNA replication, or interruption of protein synthesis.	Polyethyleneimine (PEI) biofilms: polyethyleneimine (N,N-dodecyl,methyl-PEI)	[223]
		Cationic Antimicrobial Peptide (AMP) loaded with calcium phosphate	[224]
		Peptide derived from the Parotid Secretory Protein (PSP)	[225, 226, 227, 228, 229]
		Collagen-mimetic protein and synthetic peptides	[230], [231]
		Anodic oxidation of F, Zn, Ca, Cl, I, Cu, Ce, or Se ions	[232, 233, 234, 235, 236, 237, 238, 239, 240, 241]
		Bioactive (photo-functionalized) titanium dioxide (TiO2) and reactive oxygen species	[242, 243, 244, 245, 246, 247]
		Copper, zinc, magnesium, silver, and gold nanoparticles (size ranging between 1 and 100 nm)	[248, 249, 250, 251, 252, 253, 254, 255, 256, 257]
		Chemical agents: Hydrogen peroxide (H2O2), tooth whitening gel, and citric acid	[258, 259, 260, 261]
		Antibiotics with controlled release and incorporated into polyurethane coatings, biodegradable polymers, and calcium phosphates (carbonate and porous hydroxyapatite)	[262, 263, 264, 265, 266, 267, 268]
		Hydroxyapatite (HA) with silver (Ag+) biocide ions	[248], [269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280]
High-Velocity Oxygen Fuel (HVOF) thermal spraying technology	In this process, as-cast or partially molten nanosized titanium powders are deposited on titanium substrates at a high velocity via plasma spraying to form a coating that is then biofunctionalized.	Collagen layers loaded with gentamicin	[281]
		Biofilms with silver nanoparticles	[282, 283, 284]
		Hydroxyapatite (HA) doped with silver and strontium ions	[285, 286, 287, 288]
Plasma-Immersion Ion Implantation (PIII)	This technique seeks to form a plasma layer on the material substrate, where an exchange of positive ions from the plasma with electrons from the material occurs, by implanting an oxide layer of these ions on the surface of the material.	F, Zn, Ag+, P, and Mg ions	[239], [289, 290, 291, 292, 293]
Physical Vapor Deposition (PVD)	Process whereby an inorganic or organic metal is deposited on a conductive matrix via vaporization in high vacuum conditions. This method makes it possible to obtain substrates with good resistance to degradation and a low environmental impact.	Bioactive titanium oxide (TiO2) + hydroxyapatite (HA) loaded with antibiotics.	[294]
		TiAgN and TiN thin film	[295], [296]
Graphene and its derivatives	A thin film of graphene oxide (GO) with metallic nanoparticles is formed by means of the chemical vapor deposition of graphene on titanium materials via the wet transfer method using polymethyl-methacrylate and a subsequent heat treatment for stabilization.	Silver (Ag) nanoparticles on graphene oxide	[297, 298, 299, 300, 301]
		Graphene oxide (GO) with minocycline	[302]
By means of chemical modification techniques
Chemical Vapor Deposition (CVD)	A metal coating is deposited on a substrate by thermal decomposition or chemical reaction near the hot material while controlling layer thickness, topography, and purity of the deposit.	Thin layer of graphitic C3N4 on TiO2 nanotubes	[303]
		Graphene sheets	[304]
Sol–gel	Mineral phases are formed as thin films on titanium substrates by the polymerization of molecular precursors from a colloidal solution or sol containing organic molecules or nanomaterials.	Silica sol–gels with vancomycin	[305], [306]
		ZnO films with Ag	[307]
		Copper (II) acetate in TiO2	[308, 309, 310]
		Silica compound with AgNP (AgNP/NSC)	[311]
		Ag/HA or Ag/TiSi film	[278], [312]
Titanium nitride (TiN)	Process used to improve the surface properties and finish of metals. It offers an excellent chemical stability and high resistance to high temperatures and corrosion. Nitride coatings have a high hardness and low coefficient of friction, which demonstrates their good biocompatibility when applied as layers on titanium implants.	Studies into the efficacy of nitride coatings in reducing bacterial adhesion are few and far between.	[296], [313, 314, 315, 316, 317, 318]
By means of physical and chemical modification techniques
Plasma spraying and electrochemical deposition	Metallic implants are coated with bioactive calcium phosphate (CaP) ceramics that form an osteoconductive surface that stimulates bone growth and improves prosthesis adhesion. They can also induce the accumulation of osteoblast-like cells and minimize bone cell inflammation problems. CaP biomaterials provide metal substrates with good bioactivity, thus enhancing and accelerating fixation.	CaP biomaterials: -Hydroxyapatite (HA) -β-tricalcium phosphate, Ca3(PO4)2 -Biphasic calcium phosphate, an intimate mixture of hydroxyapatite and beta-tricalcium phosphate -Unsintered CaP or a calcium-deficient apatite (Ca,Na)10(PO4 HPO4)6(OH)2	[319, 320, 321]