Aging effect of atmospheric air on lithium disilicate ceramic after nonthermal plasma treatment

Statement of problem Nonthermal plasma (NTP) treatment is an alternative technique for promoting the adhesion of resin cement to lithium disilicate ceramic. However, no study has evaluated whether the surface modifications are affected by atmospheric air aging. Purpose The purposes of this in vitro study were to characterize the lithium disilicate surface after depositing an organosilicon film with NTP treatment and to verify the surface energy before and after atmospheric air aging up to 30 days. Material and methods Sixteen lithium disilicate disks (10×3 mm) were prepared, and their surfaces were treated with a mixture of hexamethyldisiloxane and argon, followed by oxygen plasma treatment, both for 30 minutes. The lithium disilicate surface was characterized through scanning electron microscopy, energy-dispersive spectroscopy, and atomic force microscopy. Surface energy analysis was performed before (T0) and immediately after NTP treatment (T1) and after atmospheric air aging for 7 (T2), 15 (T3), and 30 days (T4). Data were submitted to analysis of variance followed by the Tukey HSD test (α=.05). Results Carbon, oxygen, and silicon were identified on the disilicate surface after NTP treatment, suggesting organosilicon film adhesion. Air aging did not modify the film morphology. At T1, the surface energy was significantly higher compared with other periods, and the water contact angle on the disilicate surface was reduced to 0 degrees. Similar surface energy was observed for T0, T2, T3, and T4. Conclusions On the basis of the results of this in vitro study, NTP treatment can promote bonding to lithium disilicate surfaces because of its high surface wettability. However, after air aging, the wettability was not durable.