Influence of ultraviolet photofunctionalization on the surface characteristics of zirconia-based dental implant materials

Objectives: To examine the effect of ultraviolet light (UV) treatment on the surface characteristics of two acid-etched zirconia-based dental implant materials.

Methods: Discs of two zirconia-based materials (Zr1 and Zr2) with smooth (m) and roughened (r) surfaces were treated by UV light for 15min. The surface topography was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface elemental composition of all samples was determined by X-ray photoelectron spectroscopy (XPS), the crystalline property by X-ray diffraction (XRD) and the hydrophilic status by contact angle (CA) measurements of a water droplet.

Results: SEM and AFM revealed quantitative and qualitative differences between the roughened and smooth surfaces. UV treatment did not induce any topographic changes of the tested surfaces (p>0.05). All UV-treated samples showed a significant surface elemental content change with a decrease of carbon by 43-81%, an increase of oxygen by 19-45%, and an increase of zirconia by 9-41%. Upon UV treatment, a 19-25% increase of the crystalline monoclinic phase was observed on surfaces of material Zr1, whereas a slight increase on the smooth Zr2 surface (+3%) and a decrease on the roughened Zr2 surface by 20% was observed. For all samples, the hydrophilic status changed significantly from hydrophobic to hydrophilic by UV treatment (p<0.0001). The average contact angles were between 56.4° and 69° before and 2.5° and 14.1° after UV-light treatment.

Significance: UV treatment altered the physicochemical properties of the two zirconia implant surfaces investigated. The mechanism by which such changes are induced requires further investigation.