## 4 Results
### Dimensional Stability and Thermal Expansion Studies
Figure 11: The results of the studies on the relative length change [%] as a function of temperature during cyclic heating and cooling tests on the samples made of NextDent C&B are presented. The tests were conducted with fixed pressing forces applied in each series: F = 80.0 mN and F = 320.0 mN. Figure 12: The results of the studies on the relative length change [%] as a function of temperature during cyclic heating and cooling tests on the samples made of Graphy TC-80 DP are presented. The tests were conducted with fixed pressing forces applied in each series: F = 80.0 mN and F = 320.0 mN. To facilitate interpretation of the results, Table 2 presents the averaged thermal expansion coefficient values over 5 \({}^{\circ}\)C intervals, highlighting temperature-dependent trends in material expansion. Based on the average \(\alpha\) coefficient values presented in Table 2, Figure 13 illustrates the increments in values across each specified interval to highlight the differences in thermal expansion changes for each of the tested materials. \begin{table}
\begin{tabular}{r r r r r r r r r r r r} \hline \hline
**Temperature (\({}^{\circ}\)C)** & \multicolumn{11}{c}{\(\alpha\) (10\({}^{-6}\)/K)} \\ \hline  & \multicolumn{4}{c}{**NextDent C\&B MFM Bleach**} & \multicolumn{4}{c}{**NextDent Dententure 3D**} & \multicolumn{4}{c}{**Graphy TC-80 DP**} \\ \hline
**Course:** & **2 nd** & **3 rd  
The conducted studies revealed that the largest increases in the thermal expansion coefficient \(\alpha\) occur in the temperature range of 31-35 \({}^{\circ}\)C for all the tested resins. In subsequent intervals, up to a temperature of 50 \({}^{\circ}\)C, the increases in \(\alpha\) gradually decrease. Beyond 50 \({}^{\circ}\)C, the increases (\(\Delta\)) in \(\alpha\) become minimal. The largest increases in \(\alpha\) within the specified temperature ranges were observed for NextDent Denture 3D, while the other resins exhibited smaller increases. This indicates that the dimensional changes caused by temperature increases were significantly less dynamic for NextDent C&B Bleach and Graphy TC-80 DP, making them more stable under thermal variations. Table 3 summarizes the thermal expansion studies, expressed as the cumulative values of the linear thermal expansion coefficient over the entire measurement range, from 25 \({}^{\circ}\)C to 63 \({}^{\circ}\)C.  
Analysing the cumulative values of the thermal expansion coefficients \(\alpha\) (10\({}^{-6}\)/K) presented in Table 3, it is evident that the materials NextDent C&B MFH Bleach and Graphy TC-80 DP exhibit similar tendencies to change their linear dimensions as a result of temperature variations. In contrast, the material NextDent Dent \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Coefficient** & & & & \(\alpha\) (10\({}^{-6}\)/K) & & & \\ \hline
**Temperature/Material** & **25–30 \({}^{\circ}\)C** & **31–35 \({}^{\circ}\)C** & **36–40 \({}^{\circ}\)C** & **41–45 \({}^{\circ}\)C** & **46–50 \({}^{\circ}\)C** & **51–55 \({}^{\circ}\)C** & **56–60 \({}^{\circ}\)C** \\ \hline NextDent C\&B MFH Bleach & 52.0 & 71.7 & 86.4 & 99.8 & 108.9 & 112.4 & 115.4 \\ NextDent Denture 3D & 53.5 & 88.2 & 112.7 & 132.4 & 147.7 & 147.8 & 153.8 \\ Graphy TC-80 DP & 56.0 & 68.8 & 79.2 & 85.0 & 90.5 & 92.3 & 94.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values of the coefficient of linear thermal expansion \(\alpha\) in Series A (F = 80 \(\mu\)N) in the given temperature ranges. Figure 13: Comparison of the value determining the increase (\(\Delta\alpha\)) of the coefficient of thermal expansion in the given temperature ranges. propensity for elongation (\(\alpha\) = 123.6) due to increasing temperature. This characteristic may be significant when selecting this material for prosthetic or dental applications, especially if the material is expected to operate within the tested temperature range.