Micro-morphological Changes Of Various CAD-CAM Blocks After Different Surface Treatments

Objectives: To evaluate the effect of different surface treatments on the micro-morphological structure of 6 different CAD-CAM blocks.
Methods: Each CAD-CAM block (Celtra Duo, Dentsply; IPS Empress CAD and IPS e.max CAD, Ivoclar Vivadent; Lava Ultimate, 3M ESPE; Vita Enamic and Vita Mark II, VITA Zahnfabrik) was sectioned with a diamond blade to produce rectangular micro-bars. They were randomly divided into 3 groups and were treated either with SiC paper (600-grit, Buehler), sandblasted using 27-μm Al₂O₃ (Danville), or subjected to tribochemical silica coating (30-μm CoJet, 3M ESPE). Subsequent treatments involved either etching with 5% hydrofluoric acid (HF; IPS Ceramic Etching Gel, Ivoclar Vivadent) during 60 sec for all CAD-CAM blocks except for IPS e.max CAD (20 sec) and Celtra Duo (30 sec), silanization using a universal ceramic primer (Monobond Plus, Ivoclar Vivadent) applied for 60 sec, etching with HF followed by silanization, or no further treatment (control). All treated specimens were processed for scanning electron microscopy (SEM; JSM 6610LV, JEOL).
Results: SEM revealed different surface topographies. The surfaces appeared relatively smooth after polishing with SiC paper. The surface topography after sandblasting exhibited shallow irregularities. Tribochemical silica coating resulted in smoother surfaces with silica particles deposited onto the surface. HF etching had a very aggressive effect on the surface of all CAD-CAM blocks regardless of the other conducted treatments: bean-like crystals (Celtra Duo); honey comb-like irregularities (IPS Empress CAD); elongated crystals (IPS e.max CAD); resin matrix with embedded nano-particles (Lava Ultimate, Vita Enamic); irregular ceramic particles (Vita Mark II). Silanization slightly modified the basic topography obtained with previous treatments; it only became smoother.
Conclusions: The surface micro-morphology of different CAD-CAM blocks depends on the ceramic composition and different surface treatments, with the greatest impact resulting from HF etching.