Comparison of the effects of laser systems and cold atmospheric plasma on the surface roughness and shear bond strength of flexible hybrid ceramics.

The aim of this study was to compare the effects of laser systems and cold atmospheric plasma (CAP) on the surface roughness (Ra) and shear bond strength (SBS) of flexible hybrid ceramics (FHCs). Eighty FHC samples were divided into 5 groups to be subjected to surface treatments (hydrofluoric acid (HFA), HFA + 5 W Er: YAG laser (HFA + 5WE), HFA + 3 W Er: YAG laser (HFA + 3WE), HFA + ultrafast fiber laser (HFA + FL), and CAP). The Er: YAG laser (AT Fidelis Plus III, Fotona, Slovenia) was operated with a 0.9 mm diameter tip, delivering 250 mJ and 150 mJ per pulse, with output powers of 5 W and 3 W, and fluences of 23,623 J/cm² and 14,157 J/cm², respectively, at a frequency of 20 Hz and a pulse duration of 600 µs for 30 s. The FL (FiberLAST Inc., Turkey) was applied with a 7 mm spot size, 1 mJ pulse energy, 20 W output power, 100 kHz repetition rate, ultrashort pulse length (100 ns), and the fluence of 1,820 J/cm² for 7 s. The CAP (PiezoBrush PZ3, Relyon Plasma, Germany) applied to the surfaces for 80 s at a treatment speed of 5 cm/s and 100% plasma power. After the Ra values were measured, each group was divided into 2 subgroups to be cemented with total-etch (TE) and self-adhesive (SA) resin cements. The SBS of all the samples was measured. One sample was randomly selected from each group, and the fractured surfaces were examined by SEM analysis. The significance level was at P < 0.05. HFA + FL had the highest Ra values, and there was no significant difference between HFA + FL and HFA + 5WE (P > 0.05). There was no difference in Ra between CAP and HFA (P > 0.05). The highest SBS values were observed for the samples cemented with TE after HFA + FL. The difference between the SBS values of the groups cemented with TE after CAP, HFA + 5WE, HFA + 3WE, and HFA + FL was not significant (P < 0.05). The use of FL may be a promising method to improve SBS without causing thermal damage when using TE or SA cements. CAP can be recommended as a practical and safe treatment with SA cement because it is suitable for chairside use with a handheld device and does not change the physical properties of the material.