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Dental implants made of pure titanium suffer from abrasion and scratch during routine oral hygiene procedures. This results in an irreversible surface damage, facilitates bacteria adhesion and increases risk of peri-implantitis. To overcome these problems, titanium nitride (TiN) coating was introduced to increase surface hardness of pure titanium. However, the osteoconductivity of TiN is considered to be similar or superior to that of titanium and its alloys and therefore surface modification is necessary. In this study, TiN coating prepared through gas nitriding was partially oxidized by hydrothermal (HT) treatment and ozone (O 3 ) treatment in pure water to improve its osteoconductivity. The effects of HT treatment and O 3 treatment on surface properties of TiN were investigated and the osteoconductivity after undergoing treatment was assessed in vitro using osteoblast evaluation. The results showed that the critical temperature for HT treatment was 100 °C since higher temperatures would impair the hardness of TiN coating. By contrast, O 3 treatment was more effective in oxidizing TiN surfaces, improving its wettability while preserving its morphology and hardness. Osteoblast attachment, proliferation, alkaline phosphatase (ALP) expression and mineralization were improved on oxidized specimens, especially on O 3 treated specimens, compared with untreated ones. These effects seemed to be consequences of partial oxidation, as well as improved hydrophilicity and surface decontamination. Finally, it was concluded that, partially oxidized TiN is a promising coating to be used for dental implant. [ABSTRACT FROM AUTHOR]

Dental implant made of pure titanium (Ti) is prone to scratch and abrasion during routine oral hygiene procedures. This results an increase in surface roughness and therefore, facilitates the adhesion of bacteria. In severe cases, this could lead to peri-implantitis. To overcome this problem, surface modification of Ti is necessary to improve its abrasion resistance. Besides, a strong implant–gingiva interface should also be guaranteed to prevent the adhesion of bacteria. In this study, titanium nitride (TiN) coating was first prepared with gas nitriding to increase surface hardness of pure the substrate. Then, the TiN was hydrothermally treated in CaCl 2 solution in order to improve its soft tissue biocompatibility. The effect of hydrothermal treatment temperature on surface properties of TiN was investigated and its biocompatibility was assessed in vitro using NIH3T3 fibroblast cell. It was determined that 120 °C was the critical temperature for the hydrothermal treatment condition. Treatment below 120 °C could incorporate Ca into TiN surface, oxidize TiN surface partially and then improve the wettability while preserving its morphology and hardness. Fibroblast cell attachment and proliferation were improved and cell spreading was enhanced on hydrothermally treated specimens compared with untreated ones. Improved wettability, Ca incorporation and negative surface due to interstitial N were believed to be the main reasons. Hydrothermal treatment is expected to make TiN a promising dental implant coating with excellent abrasion resistance and good soft tissue affinity. [ABSTRACT FROM AUTHOR]

• Hydrothermal treatment was applied to TiN coating for surface oxidation. • Anatase nanoparticle and nanolayer were formed on TiN. • Corrosion resistance of TiN was greatly enhanced even in present of fluoride ions. Titanium nitride (TiN) coating is a promising to be used on metal implant and surface oxidation by hydrothermal treatment has been proved to effectively enhance its osteoconductivity. In this study, the physicochemical properties and corrosion resistance of the TiN coating after hydrothermal treatment in distilled water were investigated. The results showed that, Anatase-type titanium oxide (TiO 2) nanoparticles formed on the TiN surface once the temperature was over 150 °C and that they formed a compact layer when the temperature increased to over 200 °C. The treatment significantly improved the wettability of TiN coating. Although surface hardness of TiN coating decreased slightly after formation of oxide layer, it could still provide enough protection for substrate. Electrochemical experiments showed that corrosion resistance of TiN was greatly improved in present of fluoride ions (F−). Immersion test for 5 weeks showed that numerous corrosion pits appeared on untreated TiN coating, whereas, the TiO 2 layer on treated TiN coating remained intact and provided good protection for the underlying TiN. This work showed that hydrothermal treatment at 200–250 °C could comprehensively improve the properties of TiN coating necessary for biological applications and it also provide a possible solution to improve corrosion resistance of hard TiN coating on metal substrates. [ABSTRACT FROM AUTHOR]

Surface oxidation is found to improve the osseointegration of titanium nitride (TiN) coatings on implantable titanium devices; nevertheless, systematic studies on effects of oxidation are still needed. In this study, multi-arc ion plated (MAIP) titanium nitride (TiN) coating was hydrothermally oxidized in pure water and then the structural, corrosion and wear properties of the coating were studied. A dense oxide layer of 20–50 nm in thickness is formed on TiN after hydrothermal oxidation above 200 °C. The layer is composed of flat anatase particles with a length of 50–150 nm and smaller anatase nanocrystallines located on their surface. The passivation behavior of TiN becomes much stronger in simulated saliva after oxidation treatment, showing a wider passivation range, a lower corrosion current and greatly improved impedance. In addition, the open circuit potential (OCP) of oxidized TiN remains much higher than that of untreated after 50 days of immersion. Sliding friction experiments against zirconia (ZrO 2) ceramic balls show that the wear type for the untreated TiN coating involves severe plowing and deformation. In contrast, only slight plowing is found on the surface of TiN covered with a compact anatase layer; the friction coefficient decreases sharply and the wear loss decreases obviously. [Display omitted] 1. Anatase nanolayer forms on TiN coating after hydrothermal oxidation in water. 2. Hydrothermal oxidation improves corrosion resistance of TiN in artificial saliva. 3. Anatase nanolayer contributes to obvious lubrication and wear reduction. [ABSTRACT FROM AUTHOR]

• Hydrothermal oxidation at 200–250 °C synthesized in situ anatase nanolayer on TiN coating. • Ultrastructure of transition zone of several-atom-layer-thick was revealed. • Corrosion resistance of TiN in F- containing acidic solution was greatly improved. To improve the corrosion resistance of titanium nitride (TiN) coating in acidic solution containing fluoride ions (F-), surface hydrothermal oxidation was conducted. Pure water was used as the medium and at temperatures as low as 200–250 °C, a thin, uniform and dense titanium oxide (TiO 2) nanolayer composed of well-crystallized anatase nanoparticles was fabricated. The TiO 2 layer was grown in situ , and its (0 0 4) planes aligned well with the (1 1 1) planes of underlying TiN; the transition zone was only a few atomic layers thick. Hydrothermal oxidation improved the chemical stability and decreased the corrosion rate of TiN coating in 0.5 mol/L sulfuric acid solution containing 0.05 wt% F-. When fabricated at 250 °C, the TiO 2 layer remained intact after immersion test, providing good protection for the underlying TiN. [ABSTRACT FROM AUTHOR]