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. 2020 Oct 15;13(20):4594. doi: 10.3390/ma13204594

Table 1.

Summary on researches about metallic antibacterial surface treatments of dental and orthopedic materials.

Antibacterial Metallic Agents Speciation Treating Components Treated Substrate Treating Techniques Action against Biofilms Results Mentioned Antibacterial Mechanisms Application Reference
Ag Ionic Ag and Sr loaded nanotubular structures Ti Anodization & hydrothermal method MSSA,
MRSA,
E. coli 		Controllable release of Ag and Sr;
Ag: anti-adherent & bactericidal activities against bacteria;
Sr: accelerated filling of bone defects.		 Not mentioned Bone/dental implants Cheng et al. [18]
Metallic Ag SS,
NiTi		 Thermal vacuum evaporation method L. acidophilus Anti-adherent effect against bacteria. Ag binds to key functional groups of enzymes. Orthodontic wires Mhaske et al. [19]
NPs Immobilized AgNPs SLA-Ti Silver plasma immersion ion implantation F. nucleatum,
S. aureus 		Good defense against multiple cycles of bacteria attack & excellent compatibility with mammalian cells. Ag0 rendered by AgNPs with electron trapping capability disrupts the integrity of bacterial membranes. Dental implants Zhu et al. [20]
NPs AgNPs, TiO2 and nano HA Ti alloy (Ti6Al4V) Silver plating, anodization & sintering techniques S. sanguinis Inhibition of bacterial growth in the surrounding media and biofilm formation on the implant surface, maintaining the HA biocompatibility. Direct contact toxicity with small but effective slow release of Ag; oxidative stress from free radicals generated by Ag-TiO2-HA. Dental implants Besinis et al. [21]
NPs AgNPs OEM Bioreduction of AgNO3 S. mutans,
L. casei,
S. aureus,
E. coli 		Inhibiting growth of bacteria and enhancing physical properties. AgNPs inhibits theenzymes of the cell respiratory cycle and damages DNA synthesis, leading to cell death. OEM Hernández-Gómora et al. [22]
NPs AgNPs and GO Ti Electroplating & ultraviolet reduction methods P. gingivalis, S. mutans Excellent antimicrobial ability and anti-adherence performance. AgNPs causes bacterial DNA damage, interruption of cell signal transduction, oxidative damage of ROS, intracellular contents leakage and dehydrogenase inactivation. Dental implants Jin et al. [23]
NPs AgNPs loaded a-C:H matrix Ti GAS & PE-CVD process E. coli,
S. aureus 		Controlled release of Ag+, excellent antibacterial performance and good biocompatibility. The antibacterial efficacy of AgNPs coating is associated with their ability to release Ag+. Orthopedic implants Thukkaram et al. [24]
NPs AgNPs and PNIPAAm Glass One-step photopolymerization method E. coli “Smart” antibacterial capability to attach, kill, and release bacteria in response to the change in environmental temperature. AgNPs releases Ag+ to affect the metabolism of E. coli and weaken the interaction between E. coli and the substrate. Biomedical materials Yang et al. [25]
Zn Ionic Zn2+ & Mg2+ Ti Plasma immersion ion implantation P. gingivalis,
F. nucleatum,
S. mutans 		Inhibition of oral anaerobic bacteria, good osteo-inductivity and proangiogenic effects. Inhibiting bacterial adhesion and growth by Zn2+ release and ROS generation. Dental implants Yu et al. [26]
Metallic Zn/Sr-doped microporous TiO2 Ti Microarc oxidation S. aureus Inhibiting bacterial colonization and proliferation with biocompatibility. Zn2+ inhibits bacterial growth via inducing cell lysis and cytoplasmic leakage. Dental implants Zhao et al. [27]
Ionic Zn-MMT Mg alloy AZ31 Hydrothermal method E. coli,
S. aureus 		Sustained-release of Zn2+, good antibacterial activity, biocompatibility and corrosion resistance. Zn-MMT leads to severe breakage of bacterial membrane; sustainable release of Zn2+ around. Orthopedic applications Zou et al. [28]
Oxide NPs Nano ZnO & isocyanate resin 3Y-ZrO2 ceramics Thermal spray coating process E. coli,
S. aureus 		Broad-spectrum antibacterial behavior, no obvious noticeable tissue damage in all major organs of mice. Not mentioned. Ceramic implants Li et al. [29]
Oxide NPs N-halamine labeled ZnO, silica PSA NPs Ti Electrostatic adsorption P. aeruginosa,
E. coli,
S. aureus 		Excellent antibacterial activity, good biocompatibility toward the preosteoblast. Making bacterial membranes distorted and incomplete. Implants Li et al. [30]
Ti Oxide NPs Nanostructured TiO2 Ti Temperature-controlled atomic layer deposition MSSA,
MRSA,
E. coli 		The coating with a moderate surface energy showed relatively promising antibacterial properties and desirable cellular functions. Photoactivated TiO2 destructs bacteria; increased surfaces roughness at the nano-scale limits the number of anchoring points for bacteria. Orthopedic implants Liu et al. [31]
Oxide TiO2 Autopolymerizable acrylic resin Spin-coating methods S. mutans,
S. sobrinus,
S. gordonii,
S. oralis,
S. sanguinis,
S. mitis 		Antibacterial effects were discovered against early colonizers and cariogenic species. TiO2 induces hydroxyl radical attack, leading to bacterial cytoplasmic membrane. Removable orthodontic resin-based retainer Kuroiwa et al. [32]
Oxide TiO2 SS Sol-gel thin film dip-coating method S. mutans,
P. gingivalis. 		Antiadherent and antibacterial properties. TiO2 breaks down the cell wall of bacteria. Orthodontic
wires		 Chun et al. [33]
Oxide TiO2 codoped with nitrogen and bismuth Ti Plasma electrolytic oxidation S. sanguinis,
A. aeslundii 		Antibacterial properties in darkness, with a stronger effect after visible-light application, noncytotoxic effect on fibroblast cells. Photocatalytic effect of TiO2 generates ROS to decompose bacterial organic compounds. Dental implants Nagay et al. [34]
Oxide Sol-gel derived anatase TiO2 coating Porous ceramic scaffolds Sol-gel derived anatase coating, catalytic decomposition of H2O2 in dark S. epidermidis Antibacterial activity, particularly at the early stages of S. epidermidis biofilm development, no cytotoxic effects. Presence of the superoxide anion via dark catalysis of TiO2 and a ROS-mediated killing mechanism. Bone Scaffolds Wiedmer et al. [7]
Cu Metallic Cu UHMVPE Low temperature aerosol assisted chemical vapor deposition E. coli,
S. aureus 		Potent dark bactericidal activity with 99.999% reduction in bacterial number within 15 min. Generated ROS triggers oxidation of unsaturated fatty acid in the cell membrane; proteins and DNA degradate. Prosthetic joint Wu et al. [35]
Metallic Cu and a supersaturated phase (S-phase) Austenitic SS Active screen plasma alloying technology E. coli Quick bacterial killing rate and durability. Cu interacts with the thiol groups of bacterial proteins and enzymes to inactivate bacteria. Medical devices Dong et al. [36]
Ionic Cu-doped chitosan-gelatin nanocomposite coating Ti Electrophoretic deposition method E. coli,
S. aureus 		Antibacterial, angiogenic, and osteogenic properties, with low cytotoxicity. Cu destroys the permeability of bacterial membranes, leading to leakage of bacterial proteins. Ti-based materials Huang et al. [37]
NPs Cu nanocubes deposited TiO2 nanotubes Ti Anodic oxidation and pulsed electrodeposition E. coli,
S. aureus 		High bactericidal potential with complete death of bacteria. Preferential release of Cu+ is considerably more toxic to bacteria than Cu2+. Dental implants Rosenbaum et al. [38]
NPs CuNPs PEEK Magnetron sputtering technique MRSA Direct antibacterial and indirect immunomodulatory antibacterial effects against MRSA. Contact-killing effect: destroy permeability of bacterial membranes, cell respiration; genetic toxicity. Implants Liu et al. [39]
Ionic Chitosan loaded with MSN@GHK-Cu (glycyl-L-histidyl-L-lysine-Cu2+) Ti Electrophoretic deposition E. coli,
S. aureus 		Inhibited adhesion of bacteria but with good cytocompatibility. Cu2+ changes bacterial membrane permeability, induces ROS generation, destroys cell structures and metabolic process. Orthopedic and dentalimplants Ning et al. [40]
Mg Metallic,
alloy		 Mg or Mg45Zn5Ca Ti Magnetron sputtering S. epidermidis Antibacterial properties and low cytotoxicity levels. Corrosion of Mg and its alloys results in shift in pH, killing bacteria by osmotic shock and inhibiting bacterial adhesion. Implants Zaatreh et al. [41]
Ionic Mg-doped TiO2 Ti Plasma electrolytic oxidation S. aureus Inhibiting bacterial colonization and growth; promoting osteoblast adhesion, proliferation and differentiation. Mg2+ penetrates bacterial cell walls, degenerates bacterial proteins, abolishes the activity of bacterial synthetase and causes bacteria to lose proliferation ability. Implants Zhao et al. [42]
Oxide NPs MgO NPs HA Ionotropic gelation method E. coli,
S. aureus 		Reduced bacterial growth and biofilm formation in a concentration-dependent manner Physical membrane damage; non-ROS mediated toxicity; non-Mg2+ release toxicity. Bone substitutes Coelho et al. [43]
Au NPs AuNPs & 4,6-diamino-2-pyrimidinethiol PS, PVC, PP, PE, PDMS, SiO2 Electrostatic self-assembly E. coli,
P. aeruginosa,
K. pneumoniae,
S. aureus,
MDR E. coli,
MDR P. aeruginosa,
MDR K. pneumoniae 		Outstanding antibacterial activity against Gram-negative bacteria on a variety of surfaces. Immobilized AuNPs disrupts bacterial cell membranes. Medical devices Zheng et al. [44]
Ta Metallic Ta SLA-Ti Magnetron-sputtering technique F. nucleatum,
P. gingivalis 		Excellent antimicrobial activity, promoted osseointegration of implants. Ta inhibits bacterial ATP synthesis, promotes ROS generation and eventually disrupts cellular metabolism. Dental implants Zhang et al. [45]
Ni NPs Ni or bimetallic Cu–Ni NPs None Synthesized in aqueous solution without using stabilizers. E. coli,
S. aureus,
S. mutans 		Exhibiting only bacteriostatic effect. Bacteriostatic effect, without bactericidal effect. Dental materials Figueroa et al. [46]

Abbreviation: Ag: silver. Sr: strontium. Ti: titanium. MSSA: Methicillin-sensitive Staphylococcus aureus. MRSA: methicillin-resistant Staphylococcus aureus. E. coli: Escherichia coli. SS: stainless steel. NiTi: nickel-titanium. L. acidophilus: Lactobacillus acidophilus. NPs: nanoparticles. SLA: sand-blasted, large grit, and acid-etched. F. nucleatum: Fusobacterium nucleatum. Ag0: neutral metallic silver. S. aureus: Staphylococcus aureus. TiO2: titanium oxide. HA: hydroxyapatite. S. sanguinis: Streptococcus sanguinis. OEM: Orthodontic elastomeric modules. AgNO3: silver nitrate. S. mutans: Streptococcus mutans. L. casei: Lactobacillus casei. DNA: deoxyribonucleic acid. GO: graphene oxide. P. gingivalis: Porphyromonas gingivalis. ROS: reactive oxygen species. a-C:H: amorphous hydrocarbon. GAS: gas aggregation source. PE-CVD: plasma-enhanced chemical vapor deposition. Ag+: silver ions. PNIPAAm: Poly(N-isopropylacrylamide). Zn: zinc. Zn2+: zinc ions. Mg2+: magnesium ions. Zn-MMT: Zn-loaded montmorillonite. ZnO NPs: zinc oxide nanoparticles. PSA: polystyrene-acrylic acid. P. aeruginosa: Pseudomonas aeruginosa. S. sobrinus: Streptococcus sobrinus. S. gordonii: Streptococcus gordonii. S. oralis: Streptococcus oralis. S. mitis: Streptococcus mitis. A. aeslundii: Actinomyces aeslundii. S. epidermidis: Staphylococcus epidermidis. Cu: copper. UHMVPE: ultra-high molecular weight polyethylene. Cu+: monovalent copper ions. Cu2+: bivalent copper ions. PEEK: polyetheretherketone. MgO: magnesium oxide. PS: polyethylene. PVC: polyvinyl chloride. PP: polypropylene. PE: polyethylene. PDMS: polydimethylsiloxane. SiO2: silica. K. pneumoniae: Klebsiella pneumoniae. MDR: multi-drug resistant. Ta: tantalum.