## 3 Results
### Overall Stresses  
The stress distribution in the frameworks was different for all three models. The CONVENTIONAL RPD model presented the highest values of effective stress, showing extensive areas with values superior to 10 MPa, as presented in Figure 5a. The mean von Mises stress was 11.3 \(\pm\) 14 MPa, ranging from 0.8 MPa to 200 MPa. Critical areas were at the \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Model** & **Ling.-Buc.** & **Post-Ant.** & **Vertical** & **Magnitude** \\ \hline \multirow{2}{*}{Conventional RPD} & 2.2 \(\pm\) 9.0 & \(-\)14.4 \(\pm\) 16.9 & 12.0 \(\pm\) 5.2 & 22.4 \(\pm\) 15.7 \\  & (\(-\)33.6 to 39.7) & (\(-\)104.4 to 24.0) & (\(-\)40.2 to \(-\)1.0) & (6.5 to 110.0) \\ \hline \multirow{2}{*}{IARPD PM} & 0.4 \(\pm\) 0.1 & \(-\)4.4 \(\pm\) 1.2 & \(-\)9.8 \(\pm\) 0.8 & 10.9 \(\pm\) 0.9 \\  & (0.08 to 0.7) & (\(-\)7.8 to \(-\)1.5) & (\(-\)12 to \(-\)7.9) & (9.1 to 13.8) \\ \hline \multirow{2}{*}{IARPD MO} & 0.1 \(\pm\) 0.5 & \(-\)0.5 \(\pm\) 0.05 & \(-\)2.2 \(\pm\) 0.4 & 2.3 \(\pm\) 0.4 \\  & (\(-\)1.0 to 1.6) & (\(-\)2.2 to 0.5) & (\(-\)3.2 to \(-\)1.3) & (1.3 to 3.3) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Displacements of the abutment teeth in all three directions, X, Y and Z, corresponding to lingual-buccal, posterior-anterior and vertical, respectively, and the corresponding magnitude. Mean \(\pm\) SD (Min-Max) (\(\upmu\)m). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Model** & **Mean \(\pm\) SD (\(\upmu\)m)** & **Range (Min-Max)** & **ANOVA** \\ \hline Conventional RPD & 730.0 \(\pm\) 80 & 530–910 & F(2, 320686) = 7825410, \\ IARPD PM & 20.0 \(\pm\) 6.0 & 3–30 & \(p<0.001\) \\ IARPD MO & 4.0 \(\pm\) 0.8 & 2–6 & \(p<0.001\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mean values and range of the magnitude of displacement of each model. Statistical analysis with one-way ANOVA. SD- standard deviation; min- minimum; max- maximum. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Pair** & **Mean Difference (\(\upmu\)m)** & **95\% CI** & \(p\)**Value** \\ \hline Conventional RPD/IARPD PM & 718 & (717,718) & \(<\)0.001 \\ Conventional RPD/IARPD MO & 730 & (729–731) & \(<\)0.001 \\ IARPD PM/IARPD MO & 12 & (11–13) & \(<\)0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean differences in the magnitude of displacement of the prosthesis (framework and acrylic) between pairs of models. Statistical analysis with two sample \(t\)-tests, assuming unequal variances and Bonferroni correction. 95% CI\(-\)95% confidence interval for the difference. direct retainers, namely the rigid portion of the retentive clasp and the minor connectors, as well as the major connector, where the maximum principal stresses are of tensile type, as can be seen in Figure 5b. In the case of the IARPD PM and IARPD MO models, there was no high stress accumulation in the direct retainers or major connector. The highest stress accumulation was in the interior portion of the matrix and surrounding material, as observed in Figure 6, and, generally, was lower than in the CONVENTIONAL RPD model. For the IARPD PM model, the mean von Mises stress value was 3.04 \(\pm\) 4.96 MPa, ranging from 462 Pa to 68 MPa, while in the IARPD MO model the von Mises stress value was of 1.81 \(\pm\) 2.37 MPa, ranging from 651 Pa to 43 MPa. The values distribution of the three models are shown in the box plot graphic presented at Figure 7. One-way ANOVA detected significant differences between models, F(2, 77087) = 8740, \(p\) < 0.001. All three models were found to be different in the pairwise comparisons presented at Table 7.  
Figure 5: Smoothed stresses distribution on the framework of the CONVENTIONAL RPD model: (**a**) von Mises stress, bottom view on the left, top view on the right; (**b**) principal stresses in the direct retainer, with all non-purple colors representing tensile stresses and the areas in pink with values superior to 100 MPa.