Self-adhesive cement adhesion to zirconia ceramic : Effect of surface treatments

Objectives: The aim of this investigation was to assess the influence of several surface treatments on the immediate shear bond strength of a self-adhesive resin cement to densely sintered zirconia ceramic. Materials and methods: 40 Densely sintered zirconia cylin- ders (d: 20mm; h: 8mm, approximately) (Lava®, 3M ESPE, St. Paul, MN) were divided into four groups (n = 10). Each of them received a different surface treatment: Group [Sand H] – ceramic blocks were air-abraded using 50 m Al2 O3 particles at a pressure of 2.8 bar/0.28 MPa; Group [Sand S] – ceramic blocks were air-abraded using 50 m Al2 O3 particles at a pressure of 1 bar/0.1 MPa; Group [HE] – an experimental etching solution (methanol, 37% HCl and ferric chloride) was heated up to 100 ◦ C and applied for 10 min. Group [No T] – no treatment. Composite cylinders were bonded with a self-adhesive resin cement (ClearfilTM SA Cement, Kuraray Medical Ltd.) to ceramic surfaces. After fabrication, specimens were stored in deionized water (37 ◦ C) for 7 days before testing. Finally, all bonded specimens were placed in a jig for shear bond strength testing and loaded to failure. The data were analyzed by one- way ANOVA model with ̨ = 0.05; surfaces were examined with a light microscope (25×) to assess the mode of failure. Further, 4 surface-treated only specimens were addressed to scanning electron microscope (SEM) analysis to evaluate topographic modifications. Results: Mean shear bond strengths (MPa) obtained from the tested samples were: [Sand H] 16.24 ± 2.95; [Sand S] 16.01 ± 2.68; [HE] 10.22 ± 1.94; [No T] 13.29 ± 1.58. No statis- tically significant difference (p = 0.8580) was found between [Sand H] and [Sand S] groups. Experimentally etched surfaces were characterized by islands of granular appearance and a high degree of topographic complexity; however, mean SBS value of [HE] was statistically lower (p < 0.05) than that of [No T]. Conclusions: Within our study limitations, low-pressure air abrasion positively affected the self-adhesive cement adhe- sion to zirconia but did not prevent scratches and microcracks formation on the ceramic surfaces.