Characterization of titanium surfaces with different treatment and aging processes

The aims of this study were to, 1) investigate the surface characteristics of polished titanium plates/discs treated with acid-etching and ultraviolet irradiation (UV); and 2) investigate the change in surface characteristics of polished titanium plates/discs treated with acid-etching and UV irradiation after aging in air, saline and citric acid for six weeks. A total of one hundred and ninety-eight commercially pure grade two titanium plates and 50 titanium discs were prepared. Titanium samples were divided into four groups: 1) polished group, 2) polished and UV group, 3) acid-etched group and 4) acid-etched and UV group. Polishing was performed by abrasive silicon carbide paper grinding. UV treatment was performed by 15W germicidal UVC, 254 nm, for 48 h. Acid-etching was performed with 67% H2SO4 at 120 ºC for 75 s. The four groups were then subjected to an aging process for six weeks in sealed containers with three different media: air, physiologic saline and citric acid. They were analyzed immediately after treatment and after aging for surface characterization: topography, roughness, wettability, crystallinity, and chemistry. The polished surface showed relatively smooth surface with typical grooves from the grinding process. Acid-etching produced micro-roughened surface with sharp pits and ridges. The average surface roughness of polished, polished-UV was lower than that of the acid-etched and acid-etched-UV surfaces (p < 0.05). Storage of titanium in saline and citric acid did not provoke any morphological or roughness changes at micron scale level when compared to the samples stored in air. Immediately after preparation and treatment, the polished and acid-etched titanium surfaces appeared to be hydrophilic with similar contact angle values (p > 0.05). After UV treatment, there was a significant reduction in contact angles (superhydrophilic) in both surfaces (p < 0.05). After storage in air for six weeks, the contact angles of the four groups significantly increased (p < 0.05) and the surfaces converted to a hydrophobic state. In contrast to samples stored in air, samples stored in saline and citric acid revealed superhydrophilic surfaces regardless of the surface type. Titanium hydride crystals were present in the acid-etched and acid-etched-UV surfaces but not in the polished and polished-UV surfaces. Titanium tetrachloride crystals were present in saline-stored surfaces. The polished surface acquired significantly higher titanium and oxygen concentrations and lower carbon contaminants compared to acid-etched surface. UV treatment substantially decreased carbon contamination and increased the titanium and oxygen concentrations in the acid-etched groups (p < 0.05). After storage for six weeks in air, the four studied surfaces had no significant changes in the surface chemistry. Storage of the titanium samples in saline and citric acid relatively increased the carbon contamination and decreased titanium and oxygen concentrations. UV treatment may be an effective way to produce clean titanium surfaces with less carbon especially after roughening the titanium surface by acid-etching. Storage of the freshly prepared titanium surface in media such as saline or citric acid could preserve the hydrophilic property of these surfaces, however, it may also negatively influence the surface chemistry due to increased carbon contaminants.

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Dental implants. ； Titanium.

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