# Martens Hardness of CAD/CAM Resin-Based Composites
## 3 Results  
The Shapiro-Wilk test confirmed the normal distribution of the tested parameters. The one-way ANOVA revealed significant differences (\(p\) < 0.001) within the parameters. Table 2 shows mean results and statistical Bonferroni post-hoc comparison. Force-indentation-curves of the investigated materials are shown in Figure 2.  
The mean Martens hardness (H\({}_{\rm M}\)) ranged from 410.8 \(\pm\) 55.8 N/mm\({}^{2}\) (KA) to 1143.4 \(\pm\) 124.7 N/mm\({}^{2}\) (VE). The ANOVA showed significant (\(p\)\(\leq\) 0.001) differences between the results (Table 2). The residual indentation depth (h\({}_{\rm r}\)) was between 13.9 \(\pm\) 0.7 \(\upmu\)m (VE) and 23.0 \(\pm\) 1.4 \(\upmu\)m (KA), with significant differences between the results (ANOVA: \(p\)\(\leq\) 0.001). The indentation hardness (H\({}_{\rm HT}\)) varied between 666.5 \(\pm\) 88.2 N/mm\({}^{2}\) (KA) and 1834.2 \(\pm\) 198.0 N/mm\({}^{2}\) (VE). The ANOVA confirmed significant (\(p\)\(\leq\) 0.001) differences between the results. The indentation modulus (E\({}_{\rm HT}\)) ranged from 8.8 \(\pm\) 1.4 kN/mm\({}^{2}\) (KA) to 25.3 \(\pm\) 3.0 kN/mm\({}^{2}\) (VE), with significant differences between the results (ANOVA: \(p\)\(\leq\) 0.001). The mean elastic part of indentation (\(\eta_{\rm HT}\)) varied between 40.2 \(\pm\) 0.5% (VO) and 50.4 \(\pm\) 4.3% (LU) (Figure 3). The ANOVA confirmed significant differences between the mean values (\(p\)\(\leq\) 0.001). The indentation creep (C\({}_{\rm IT}\)) ranged from 3.2 \(\pm\) 0.1% (VE) to 5.1 \(\pm\) 0.4% (KC). The ANOVA showed significant (\(p\)\(\leq\) 0.001) differences between the values.  
A highly significant (\(p\) < 0.01, Pearson correlation >0.576) correlation between the materials and H\({}_{\rm M}\), H\({}_{\rm HT}\) or E\({}_{\rm IT}\) was identified. Negative correlations were established for h\({}_{\rm r}\) (\(-\)0.623), and C\({}_{\rm IT}\) (\(-\)0.584). No correlation could be determined for \(\eta_{\rm IT}\) (\(-\)0.151, \(p\) = 0.227). A significant (\(p\) < 0.001) impact of the material was found on H\({}_{\rm M}\) (\(\eta^{2}\) = 0.914), H\({}_{\rm IT}\) (\(\eta^{2}\) = 0.867), E\({}_{\rm IT}\) (\(\eta^{2}\) = 0.910), C\({}_{\rm IT}\) (\(\eta^{2}\) = 0.771), \(\eta_{\rm IT}\) (\(\eta^{2}\) = 0.544), and h\({}_{\rm r}\) (\(\eta^{2}\) = 0.814).  
\begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline
**Material** & **Abbr.** & **h\({}_{\rm r}\) [um]** & **H\({}_{\rm M}\) [N/mm\({}^{2}\)]** & **H\({}_{\rm IT}\) [N/mm\({}^{2}\)]** & **E\({}_{\rm IT}\) [kN/mm\({}^{2}\)]** & **n\({}_{\rm IT}\) [\%]** & **C\({}_{\rm IT}\) [\%]** \\ \hline Cerasmart & CS & 22.8 \({}^{\rm a,b,d,f}\) & 441.3 \({}^{\rm a,b,d,f}\) & 688.5 \({}^{\rm a,b,c,d,f,g}\) & 10.2 \({}^{\rm a,b,d,f,g}\) & 48.3 \({}^{\rm a,b,c,d,f,g}\)\({}^{\rm b,c,d,f,g}\)\({}^{\rm b,c,d,f,g}\) \\  & (1.7) & (60.1) & (88.8) & (1.9) & (7.0) & (0.5) \\ Brilliant Crios & BC & 22.7 \({}^{\rm a,b,d,f}\) & 438.5 \({}^{\rm a,b,d,f}\) & 689.5 \({}^{\rm a,b,c,d,f}\)\({}^{\rm b}\) & 10.0 \({}^{\rm a,b,d,f,h}\) & 44.1 \({}^{\rm a,k}\) & 4.9 \({}^{\rm a,b,c,d,f,g}\) \\  & (0.5) & (40.4) & (40.0) & (40.0) & (1.6) & (2.1) & (0.3) \\ Etselite & EL & 19.4 \({}^{\rm a,d,c,g}\)\({}^{\rm b,h,k}\) & 602.8 \({}^{\rm c,b,h,k}\) & 940.2 \({}^{\rm a,b,c,d,f,g}\)\({}^{\rm b,h,k}\) & 13.9 \({}^{\rm c,g}\) & 45.2 \({}^{\rm a,k}\) & 4.5 \({}^{\rm a,b,c,d,g}\)\({}^{\rm b,c,d,g}\)\({}^{\rm b,c,d,f,g}\) \\  & (0.7) & (47.9) & (66.8) & (1.5) & (1.6) & (0.3) \\ Block HC & BL & 21.3 \({}^{\rm a,b,d,f}\) & 457.3 \({}^{\rm a,b,d,f,g}\) & 724.0 \({}^{\rm a,b,c,d,f,g}\)\({}^{\rm b,c,d,f,g}\) & 10.2 \({}^{\rm a,b,d,f,g}\)\({}^{\rm b,d,f,g}\)\({}^{\rm b,c,d,f