## 3 Results
### Stress Analysis in Critical Notchs of the Dentures Under 230 N and Thermal Loading  
After investigating the maximum stress distributions on maxillary dentures, it was observed that maximum stresses occurred in the incisal notch and the labial frenal notch of maxillary dentures for all the models (Figure 18). Therefore, failure may begin at these points. In maxillary dentures without reinforcement material under a 230 N loading only, the highest tensile stress recorded was 31.15 MPa at the tip of the incisal notch, while the labial frenal notch showed the highest compressive stress of \(-\)53.32 MPa. It was seen that using reinforcement materials in maxillary dentures led to reductions in stresses at the critical notches, in varying proportions. The greatest reduction was 76.15% in the CrCo-reinforced denture due to CrCo's high bending stiffness. For all the dentures with reinforcing materials shown in Table 3, it was observed that tensile stresses at the tip of the incisal notch and compressive stresses at the labial frenal notch decreased considerably with increasing temperatures from 0 \({}^{\circ}\)C to 70 \({}^{\circ}\)C.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Reinforcement Material of PMMA Denture and Value of Temperature**} & \begin{tabular}{c} **The Tensile Stress** \\ **at the Tip of the** \\ **Incial Notch,** \\ **Maximum Stress** \\ **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **The Compressive** \\ **stresses at Labial** \\ **Frenal Notch,** \\ **Minimum Stress** \\ **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **Percentage Change in** \\ **Maximum Stress** \\ **Unreinforced Denture** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **Minimum Stress** \\ **According to the** \\ **Unreinforced Denture** \\ **(\%)** \\ \end{tabular} \\ \hline \hline \begin{tabular}{c} Unreinforced 0 \({}^{\circ}\)C \\ \end{tabular} & 30.76 & \(-\)52.85 & - & - \\ \hline \begin{tabular}{c} Unreinforced 36 \({}^{\circ}\)C \\ \end{tabular} & 31.15 & \(-\)53.32 & - & - \\ \hline \begin{tabular}{c} Unreinforced 70 \({}^{\circ}\)C \\ \end{tabular} & 31.52 & \(-\)53.76 & - & - \\ \hline \begin{tabular}{c} CrCo 0 \({}^{\circ}\) \\ \end{tabular} & 15.16 & \(-\)43.94 & 50.72 & 16.86 \\ \hline \begin{tabular}{c} CrCo 36 \({}^{\circ}\)C \\ \end{tabular} & 7.43 & \(-\)39.80 & 76.15 & 25.36 \\ \hline \begin{tabular}{c} CrCo 70 \({}^{\circ}\)C \\ \end{tabular} & 4.77 & \(-\)35.88 & 84.87 & 33.26 \\ \hline \begin{tabular}{c} UniCarbon/Epoxy 0 \({}^{\circ}\)C \\ \end{tabular} & 19.11 & \(-\)51.01 & 37.88 & 3.48 \\ \hline \
\begin{tabular}{c} UniCarbon/Epoxy 36 \({}^{\circ}\)C \\ \end{tabular} & 9.94 & \(-\)42.20 & 68.09 & 20.86 \\ \hline
\begin{tabular}{c} UniCarbon/Epoxy 70 \({}^{\circ}\)C \\ \end{tabular} & 10.69 & \(-\)34.26 & 66.09 & 36.27 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Maximum and minimum stress values in critical notches of the dentures under 230 N and thermal loading.  
Figure 18: The incisal notch and the labial frenal notch of the maxillary denture.  
Since the maximum stresses occurring at the critical points of the denture do not exceed the tensile and compressive strengths, no damage occurs for all models.  
When the temperature of the maxillary denture with reinforcing material was decreased from 36 \({}^{\circ}\)C to 0 \({}^{\circ}\)C under 230 N, it was seen that the stresses of the critical notches increased. However, when the temperature of the maxillary denture with reinforcing material was increased from 36 \({}^{\circ}\)C to 70 \({}^{\circ}\)C under 230 N, it was seen that the stresses of the critical notches decreased in all models except for unidirectionally reinforced Carbon/epoxy due to its negative thermal expansion coefficient in the fiber direction.