## 6 Discussion and Conclusions  
The study was conducted to comprehensively evaluate the properties of three photopolymer 3D printing materials used as temporary dental implant restorations: NextDent Denture 3D, NextDent C&B MFH Bleach, and Graphy TC-80 DP. The goal was to find out which of these materials exhibit the best mechanical and thermal properties relevant to their clinical application. Temporary prosthetic restorations perform a key function in implant treatment, allowing patient functionality and aesthetics during the period of implant osteointegration. Dimensional stability and thermal expansion studies have shown that all the materials studied have a low coefficient of thermal expansion, making them stable under varying temperature conditions, such as those found in the oral cavity. The results of dilatometric analysis indicate that the materials maintain high dimensional stability, returning to their original dimensions after cyclic heating and cooling. This is particularly important in the context of their daily use, where the materials are exposed to a variety of temperature changes due to eating, drinking, or oral hygiene. The Graphy TC-80 DP material showed the least dimensional changes over the temperature range tested, indicating its greater stability compared to the other materials. NextDent Dent 3D, on the other hand, showed a greater tendency toward thermal expansion, which may limit its use in more demanding conditions, such as implant prosthetics for patients prone to mechanical and thermal stresses. The fatigue tests conducted under cyclic loading conditions simulating chewing forces revealed significant differences between the tested materials. Graphy TC-80 DP showed the best fatigue properties, withstanding the highest number of cycles before failure at a fixed load amplitude. The slope of its fatigue curve was the smallest among the materials tested, meaning that load fluctuations have less impact on the lifespan of this material compared to the others. This makes Graphy TC-80 DP the most suitable material for clinical applications requiring higher mechanical load resistance. NextDent C&B MFH Bleach showed average results, suggesting that the material can be used in less demanding clinical settings, such as short-term temporary restorations. NextDent Denture 3D showed the lowest fatigue resistance, indicating its limited use in situations subject to prolonged or intense cyclic loading. The results obtained in this study can be compared with the existing research on the fatigue resistance of conventional dental materials such as polymethyl methacrylate (PMMA) and acrylics. Available studies on the fatigue testing of dental materials used for temporary restorations show that PMMA-based dental resins exhibit significantly lower fatigue resistance compared to alternative fibre-reinforced or nano-filler materials [33; 34; 35]. Similarconclusions were drawn by [PERSON] et al., who found that conventional PMMA restorations tend to develop microcracks under cyclic loading, leading to progressive structural degradation [36]. Compared to these findings, the 3D-printed materials tested in this study, particularly Graphy TC-80 DP, showed superior fatigue performance, withstanding a significantly higher number of cycles before failure. This suggests that modern 3D-printed resins may offer a more durable alternative to traditional PMMA-based restorations, particularly in clinical cases where high fatigue resistance is required. Based on the analysis of the experimental results, we can distinguish several key aspects regarding the damage mechanism. In the case of the NextDent Denture 3D material, the observed microcracks and gradual deformation indicate the dominance of the plastic deformation mechanism and gradual weakening of the structure, leading to deformation in the form of a 'barrel-shaped' specimen. In the NextDent C&B MFH Bleachdominant failure mechanism was delamination at the interface between the polymer matrix and filler particles, resulting from weakened interfacial bonds.