Extensive data was searched as mentioned in the research methods. According to the data analysis, the number of papers from 2011 to 2015 was the highest at 730; the research shows a trend of rapid increase in recent years with the large number of papers from 2016 to 2018. In the author’s field of specialization, 995 fields of basic science were the most studied; fields within environmental science and basic science were extended to the medical field (Table 1). The toxicity of titanium implants revealed 734 results, including titanium corrosion and titanium hypersensitivity, 1229 articles for titanium toxicity, 149 toxicities for titanium alloy, and 256 articles for yellow nail syndrome, a titanium-related disease (Table 2).

Within the "Toxicity of titanium" section, studies with regard to liver, lung, and kidney cytotoxicity in human cells and the accumulation of titanium particles were summarized. Within the "Toxicity of titanium alloys" section, we summarized the cytotoxicity of titanium alloys and the inflammatory response of surrounding tissues caused by titanium alloys. Within the "Toxicity of titanium implants" section, we reviewed the inflammatory response to titanium corrosion, hypersensitivity to titanium, and the potential risks of nanoparticles used in titanium implants. Finally, we reviewed the toxicity of titanium by surveying yellow nail syndrome as a disease related to titanium and discussed the risks and potential risks of titanium.

Toxicity of titanium

Titanium is used in various applications such as cosmetics, paints, food products, drugs, and medical implant materials including dental implant. Currently, the most commonly used form of titanium is TiO₂ powder. As the production of TiO₂ (titanium dioxide) powder continues to expand, there has been an increase in concern of its influence on human and environment. Numerous studies reported the presence and toxicity of TiO₂ (titanium dioxide) nanoparticle in both animal models and cultured human cell.