# Degree of Conversion and Mechanical Properties of Modern Self-Adhesive Luting Agents
## 3 Results
Two-way ANOVA showed an insignificant difference in the material type (\(p\) = 0.478, \(>\)0.05), and a significant difference in the curing mode (\(p\) < 0.001), with no interaction (\(p\) = 0.805, \(>\)0.05). Full range ATR-FTIR spectra of the auto-mixed pastes of the luting agents are presented in Figure 4. The major resin peak assignments are as follows (cm\({}^{-1}\)): O-H (3442, 1140-1110), N-H (3371), aromatic C..C (3010, 1608, 1595, 1510, 830, 801), CH\({}_{3}\)/CH\({}_{2}\)/CH (2920-2880, 1465-1430, 1370-1360, 720-700), C=O (1715, 1320, 1290), C=C(1634, 1500, 895), CON-H (1540), C-O-C (1260, 1105-1000) and Si-O (1150-1000). The phosphate peaks of MDP appear at 1247 (P=O) and at 1040 (P-O-C), 1111, 1014 (P-O) overlapping with the Si-O vibrations. However, the absence of the 1111 cm\({}^{-1}\) peak (P-O of MDP) from the PV5 spectrum is a characteristic finding. Figure 2: Representative force-indentation depth IIT curves for the dual-cured (**a**) and self-cured (**b**) materials tested. The left peak shifting in dual-cured materials denotes increased HM hardness, whereas the steeper the unloading curve, the higher the indentation modulus (E\({}_{\rm IT}\)). 1: PSP, 2: PSU, 3: PV5, 4: SPC, 5: THC. Representative expanded ATR-FTIR spectra used for calculation of the degree of conversion (DC%) are illustrated in Figure 5. All materials contained aromatic group peaks,  
Figure 4: ATR-FTIR spectra of unset auto-mixed pastes of the materials tested. Arrow shows the absence of the P–O peak from the PV5 spectrum (4000–650 cm\({}^{-1}\) wavenumber range, A: Absorbance scale). Figure 3: Indentation depth-time IIT curves for the dual-cured (**a**) and self-cured (**b**) products tested based on the tetragonal pulse loading (Figure 1). All the products, exempt for SPC, demonstrated lower curve profiles in dual- than light-curing modes.1: PSP, 2: PSU, 3: PV5, 4: SPC, 5: THC. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Product** & \multicolumn{2}{c}{**C\({}_{\text{IT}}\) (\%)**} \\ \hline  & DC & SC \\ \hline PSP & 5.5 (1.8)a,A & 7.3 (1.5)a,B \\ \hline PSU & 6.2 (0.7)a,A & 10.1 (1.2)a,B \\ \hline PV5 & 3.9 (1.3)a,A & 8.6 (0.7)a,B \\ \hline SPC & 5.5 (1.2)a,A & 10 (1.5)a,B \\ \hline THC & 5.1 (2.8)a,A & 9 (1.7)a,B \\ \hline \hline \end{tabular}  
* Means and standard deviations (in parentheses). Same low-case letters show mean values with insignificant differences between the products within the same curing mode, whereas same upper-case letters show mean values with insignificant differences for the same product between the two curing modes (\(p>0.05\)).  
\end{table} 
Table 3: The results of C\({}_{\text{IT}}\) for the products tested in dual-curing (DC) and self-curing (SC) modes *. which were used as reference bands, except for SPC, where the N-H vibrations were used as reference. The results of the degree of conversion (DC%) are presented in Table 4. The results passed normality and equal variance tests (\(p\) = 0.051). Between the curing modes per material, all differences were significant (\(p\) < 0.001). The only statistically significant correlation found was between HM and E\({}_{\rm{IT}}\) for the self-curing mode (\(\rho\) = 1, \(p\) = 0.0165). The microstructure and the EDX spectra of the products tested are presented in Figure 6. The quantitative results of the EDX elemental analysis are presented in Table 5. The BE images demonstrated the typical structure of particle-filled composites. The filler particles in PSP and PSU were greater than in PV5. Some particles in PSP manifested increased greyscale contrast. SPC and THC exhibited a diffuse distribution of ultrafine high-contrast particles with a greater surface area occupied in SPC. The latter demonstrated some randomly distributed bigger size particles of medium contrast. The elemental analysis showed that all products contained O, Na, Al, Si, P, Cl, and Ba.