Purpose The aim of this in vitro study was to measure the effect of staining and artificial aging on the surface roughness of commercially available resin-ceramic computer-aided design and computer-aided manufacturing (CAD/CAM) materials both quantitatively and qualitatively and to compare it to feldspathic material. Materials and methods Test specimens (n = 15 per material) were prepared of CAD/CAM ingots from a resin nanoceramic (Lava Ultimate, LVU), a polymer-infiltrated ceramic (Vita Enamic, ENA), and a resin nanoceramic (Cerasmart, CER). In the staining protocol, test specimens were (i) roughened in a standardized manner and (ii) stained with the manufacturer's recommended staining kit by means of photo-polymerization (Bluephase Polywave). The control specimens were prepared out of a feldspathic ceramic (Vita Mark II,VM2) and stained in a ceramic furnace. As negative control of each group, 15 specimens were prepared and polished in a standardized manner. Surface roughness (Ra) was measured after finishing procedures and after simulation of clinical service up to 5 years by means of toothbrushing. After each year of aging, one specimen per group was randomly selected for scanning electron microscopy (SEM) analysis. Kruskal-Wallis test and paired post-hoc test were applied to detect differences between treatment groups (alpha = 0.05). Results The mean roughness measurements of the stained CAD/CAM materials were 0.14 +/- 0.04 mu m (ENA), 0.15 +/- 0.03 mu m (LVU), 0.22 +/- 0.03 mu m (VM2), and 0.26 +/- 0.12 mu m (CER). In the polished CAD/CAM materials the measurements were 0.01 +/- 0.01 mu m (CER), 0.02 +/- 0.01 mu m (LVU), 0.02 +/- 0.00 mu m (VM2), and 0.03 +/- 0.01 mu m (ENA). Irrespective of the restoration material, the applied staining protocol resulted in a higher surface roughness compared to the polished specimens (p < 0.001). After 5 years of simulated aging the mean surface roughness in the stained CAD/CAM materials were 0.22 +/- 0.03 mu m (VM2), 0.24 +/- 0.09 mu m (ENA), 0.25 +/- 0.06 mu m (CER), and 0.37 +/- 0.09 mu m (LVU). Aging had a significant effect on surface roughness in groups ENA and LVU (p < 0.001). SEM analysis showed that the staining layer on resin-ceramic CAD/CAM materials was partially removed over time. Conclusions The applied staining protocol significantly increased surface roughness of CAD/CAM materials. Instability of the staining layer on resin-ceramic CAD/CAM materials could be anticipated over time as a consequence of toothbrushing, whereas feldspathic ceramic did not suffer from such aging effect.
