## 3 Results  
Mean values (and standard deviations [SD]) for the vertical wear and the volumetric loss obtained on each material are shown in Tables 2 and 3. According to the one-way ANOVA tests, no significant differences (\(p\) > 0.05) were observed among the experimental groups concerning both total vertical wear and total volumetric loss.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Sample Vertical** & **Antagonist Vertical** & **Total Vertical Wear** \\  & **Wear (SD)** & **Wear (SD)** & **(SD)** \\  & **A** & **B** & **A + B** \\ \hline Ena Cad & 0.061 (0.044) a & 0.140 (0.037) a & 0.202 (0.045) a \\ \hline Brilliant Crios & 0.067 (0.036) a & 0.212 (0.107) a & 0.279 (0.093) a \\ \hline Grandio disc & 0.086 (0.050) a & 0.179 (0.079) a & 0.265 (0.097) a \\ \hline Aurocast 8 & 0.076 (0.017) a & 0.141 (0.050) a & 0.217 (0.045) a \\ \hline \hline \end{tabular}
\end{table}
Table 2: Sample vertical wear (mm), antagonist vertical wear (mm) and total vertical wear (mm) mean (and standard deviations [SD]) values are summarized in the table.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Sample Volumetric** & **Antagonist** & **Total Volumetric Loss** \\  & **Loss (SD)** & **(SD)** & **Loss (SD)** \\  & **C** & **D** & **C + D** \\ \hline Ena Cad & 0.055 (0.042) b & 0.062 (0.029) a & 0.117 (0.043) a \\ \hline Brilliant Crios & 0.049 (0.030) b & 0.156 (0.128) a & 0.206 (0.118) a \\ \hline Grandio disc & 0.078 (0.066) b & 0.109 (0.092) a & 0.186 (0.125) a \\ \hline Aurocast 8 & 0.148 (0.065) a & 0.066 (0.036) a & 0.213 (0.069) a \\ \hline \hline \end{tabular}
\end{table}
Table 3: Sample volumetric loss (mm\({}^{3}\)), antagonist volumetric loss (mm\({}^{3}\)) and total volumetric loss (mm\({}^{3}\)) mean (and standard deviations [SD]) values are summarized in the table.  
Compared to Aurocast 8, modestly increased, but not statistically significant, differences were recorded on total vertical wear mean values for Brilliant Crios and Grandio disc. Slightly lower, but still not significant, differences were recorded for the total vertical wear of Ena Cad discs compared to all of the other tested materials. As for the total volumetric loss, slightly reduced, but not significant, differences were recorded for the total volumetric loss of the Ena Cad, Brilliant Crios and Grandio disc compared to Aurocast 8. SEM images of the wear facets observed on the cylindrical specimens are shown in Figure 2. The Ena Cad, Brilliant Crios and Grandio discs were quite similar in dimension for the worn areas, without important signs of chipping over the transition between worn and unworm surfaces. At 7000\(\times\) magnification (Figure 3), Ena Cad showed filler particle sizes ranging quite uniformly between 0.2 \(\upmu\)m and 3 \(\upmu\)m. Brilliant Crios showed a less homogeneous filler size range, with particles ranging between 0.1 \(\upmu\)m and 4 \(\upmu\)m. Finally, the Grandio disc showed the highest filler size, with filler particles up to 7 \(\upmu\)m.  
Figure 2: Scanning electron microphotographs at two different magnifications of the wear facets observed on representative specimens from the CAD/CAM composite materials tested: Ena Cad [(**A**), 25\(\times\); (**B**), 1500\(\times\)], Brilliant Crios [(**C**), 25\(\times\); (**D**), 1500\(\times\)] and Grandio disc [(**E**), 25\(\times\); (**F**), 1500\(\times\)].