Surface characteristics of bioactive glass-infiltrated zirconia with different hydrofluoric acid etching conditions
Gye-Jeong Oh1, Ji-Hye Yoon2, Doh-jaeLee3, Hyun-Pil Lim2, Kwi-Dug Yun2, Sang-Won Park1,2* and John G. Fisher4*
1RIS Foundation for Advanced Biomaterials, Chonnam National University, Gwangju, Republic of Korea
2 Department of Prosthodontics, Dental Science Research Institute, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea
3 NCL KOREA CO., LTD., Gwangju, Republic of Korea
4School of Materials Science and Engineering, Chonnam National University, Gwangju, Republic of Korea
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The purpose of this study was to examine the surface characteristics of bioactive glass-infiltrated zirconia specimens which underwent different hydrofluoric acid etching conditions. A total of 216 zirconia specimens were prepared. Specimens were classified into the following six groups: Zirconia, Zirliner, Porcelain, Bioactive glass A1, Bioactive glass A2, and Bioactive glass A3. Zirliner and porcelain were applied to fully sintered zirconia followed by heat treatment. Bioactive glass was infiltrated into presintered zirconia by using a spin coating method followed by complete sintering. Specimens were acid-etched with 10% or 20% hydrofluoric acid (HF) and subdivided based on etching time (1 min, 2 min, 10 min, and 1hr). Surface roughness was measured using a profiler. The surface morphology was observed by field emission scanning electron microscopy (FE-SEM). The surface roughness of the zirconia group was not affected by the etching time or the concentration of the acid. All specimens in the zirconia group had similar roughness. The roughness of the zirliner group increased as the etching time increased up to 10 min. The highest surface roughness was observed at 10 min when both concentrations (10% and 20%) of HF were used, whereas the lowest roughness was observed after 1 hr when 20% HF was used. The roughness of the porcelain group increased as the etching time and acid concentration increased. The highest roughness was 7.46 µm after 1hr of etching using 20% HF. The roughness of the etched bioactive glass groups (A1, A2, and A3) was slightly increased up until 10 min of etching. After 1 hr of etching, their roughness was considerably increased. SEM images of the zirliner group showed increased porosity according to etching time. There were few zirliner particles remaining upon the zirconia specimen after 1 hr of etching using HF 20%. Specimens of the porcelain group showed a porous and sharp network structure. Large particles with smooth edges were observed. Etched bioactive glass-infiltrated zirconia showed an increase in porosity. Within the limitations of this study, surface roughness was affected by the infiltration material, etching time, and acid concentration. Etched bioactive glass-infiltrated zirconia surfaces with micro-topographies are expected to be used as implant surfaces in a similar fashion to machined or sandblasted and acid-etched (SLA) titanium surfaces.
Keywords: Bioactive glass, zirconia, hydrofluoric acid, etching conditions, surface characteristics