Does the incorporation of zinc into TiO₂ on titanium surfaces increase bactericidal activity? A systematic review and meta-analysis

Infections associated with bacterial biofilm formation are an important cause of early implant failure. With the growing number of antibiotic-resistant bacteria, the incorporation of zinc into TiO₂ coatings of titanium implants has emerged to promote osseointegration and inhibit bacterial proliferation. However, a systematic assessment of its efficacy is lacking.

The purpose of this systematic review and meta-analysis was to assess the bactericidal effect of zinc-modified TiO₂ coatings on titanium or Ti-6Al-4V alloy.

The review was structured based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist and the peer review of electronic search strategies (PRESS) guidelines. The search was performed in Science Direct, SCOPUS, Web of Science, and PubMed databases, including experimental in vitro studies that used titanium or Ti-6Al-4V as a control group and performed bacterial assays. Meta-analysis was performed by using the standardized mean differences of antibacterial effects.

A total of 2519 articles were collected after duplicate removal. Then, eligibility criteria and a manual search were applied to select 20 studies for qualitative analysis and 16 studies for statistical analysis. The risk of bias revealed low-quality evidence. The meta-analysis showed that zinc positively affected the bactericidal activity of TiO₂ coatings (-8.79, CI_95%=-11.01 to -6.57, P<.001), with a high degree of heterogeneity (I²=78%). Subgroup analysis with TiO₂ nanotubes produced by anodization and ZnO nanoparticles by hydrothermal synthesis reduced heterogeneity to 43%, with the removal of outliers (I²=46%), with a favorable antibacterial effect for zinc incorporation into TiO₂.

Bactericidal activity was identified for zinc incorporated into TiO₂ coatings, making it an interesting option for titanium dental implants.