[Effect of different frequencies of Er:YAG laser on bond properties of zirconia ceramic].

PURPOSE: The effect of different frequencies of Er:YAG laser on bond properties of zirconia ceramic was investigated. METHODS: 3 mmx3 mm x2 mm Y-TZP blocks were randomly divided into 6 groups（n=5）：control group (C)，sandblasting group (SB) and Er:YAG laser group (A1-A4) in which the frequencies were 5, 10, 15 and 20 Hz, respectively, IPS e.max Press ceramics were used as group B. Scanning electron microscope (SEM) images were recorded for each group. The ceramics were bonded to teeth. After being stored in a constant temperature water bath at 37 ℃ for 24 hours, shear test was performed with universal testing machine. Fracture modes were evaluated with stereomicroscope. The data were analyzed with SPSS 26.0 software package. RESULTS：SEM showed that compared with the control group (C)，the surface of Y-TZP treated by Er:YAG laser with different frequencies became rough. The results of shear test showed that the highest bond strength value for IPS e.max Press ceramics group(B) was (13.15+/-2.97) MPa, followed by sandblasting group (SB): (7.78+/-0.97) MPa, and 10 Hz group (A2): (7.13+/-0.75) MPa. There was no significant difference between sandblasting group (SB) and 10Hz group(A2) (P>0.05). Fracture modes of the control group (C) were mainly interface fracture of Y-TZP and resin cement；most of the fracture modes of Er:YAG laser and sandblasting group (SB) were interface fracture of Y-TZP and resin cement，a few of mixed fracture and cohesion fracture of resin cement；and the fracture modes of IPS e.max Press ceramics group(B) were all mixed fracture. CONCLUSIONS：Er:YAG laser with 10 Hz can replace 110 mum Al(2)O(3) sandblasting for surface modification of Y-TZP, in order to increase the bonding strength between Y-TZP and resin cement.