Effect of glaze coating technique on surface characteristicsand bond strength of zirconia

Objective To investigate the effect of glaze coating technique on the surface characteristics and bond strength of zirconia ceramics.

Methods A total of 100 fully sintered zirconia specimens were prepared and randomly divided into 5 groups, with 20 specimens in each group. The zirconia surfaces of the specimens in each group were treated with five different ways: group A (control group without treatment), group B (alumina sandblasting), group C (glaze coating + etching for one time with hydrofluoric acid HF), group D (glaze coating + etching for one time with HF + silane coupling agent), and group E (glaze coating + etchings for two times with HF + silane coupling agent). The surface micromorphology, chemical element composition, roughness, and bond strength between zirconia and resin cement were compared among the groups

Results The surface roughness of zirconia specimens from highest to lowest was as follows: group C (0.68±0.05) μm, group D (0.57±0.06) μm, group E (0.48±0.04) μm, group B (0.14±0.04) μm, and group A (0.06±0.01) μm. Pairwise comparisons among the above groups showed statistically significant differences (P < 0.05). Scanning electron microscope observation revealed interlaced horizontal lines on the surface of group A zirconia specimens, irregular pits on the surface of group B zirconia specimens, and uniformly distributed pits on the surfaces of zirconia specimens in groups C, D, and E. The pits in groups D and E were denser and finer compared to those in group C. Energy dispersive spectrometry analysis of the chemical element composition on the zirconia specimen surfaces showed that group A contained only zirconium and oxygen, group B contained zirconium, oxygen, and aluminum, and groups C, D, and E contained zirconium, oxygen, and silicon. The shear bond strength of zirconia specimens from highest to lowest was as follows: group E (12.71±0.81) MPa, group D (10.82±0.75) MPa, group C (7.06±0.54) MPa, group B (4.98±0.49) MPa, and group A (3.13±0.47) MPa, and between-group differences were observed (P < 0.05).

Conclusion The glaze coating technique improves the surface roughness and bond strength of zirconia. Appropriately extending the HF etching time can further enhance the bond strength of zirconia surfaces, but the etching time should not be too long, and attention should be paid to the control of glaze coating thickness.