## 4 Discussion
These results are in line with our findings for groups 0 and 2. Despite utilizing similar autoclaving cycles (i.e., 121 \({}^{\circ}\)C, 1 bar, 20 min and 134 \({}^{\circ}\)C, 2 bar, 10 min), the varying observations could be a consequence of the different specimen preparation. In their work, the specimens were cut out of surgical templates, embedded, and coated with a gold layer to improve the visibility of the indentations prior to testing. In addition, the group conducted their tests with different parameters in terms of load (50 g) and duration (5 s). Furthermore, theyinvestigated the flexural properties by testing for changes in the flexural strength, showing that autoclaving at 134 \({}^{\circ}\)C increased the materials stiffness significantly, while there were no significant changes in the flexural properties after autoclaving at 121 \({}^{\circ}\)C. Overall, our results are not entirely comparable, as different flexural properties were tested. Still, the results found in our study show similarities to the findings of [PERSON] et al., as we found no significant changes in the flexural modulus for 121 \({}^{\circ}\)C, while detecting a significant change for one group after autoclaving at 134 \({}^{\circ}\)C. However, the limited amount of data does not allow us to draw any firm conclusions about the influence of the autoclaving parameters on the flexural properties. It would be interesting to clarify whether autoclaving-induced changes in flexural properties are minor at lower sterilization temperature and pressure [27]. Most recently, [PERSON] et al. conducted a similar study on the influence of disinfection and autoclaving on the flexural properties of surgical guide materials for additive manufacturing [29]. In contrast to our results, they found significantly increased flexural moduli for both autoclaving cycles that the specimens were subjected to (i.e., 121 \({}^{\circ}\)C, 1 bar, 20 min and 134 \({}^{\circ}\)C, 2 bar, 10 min). Reasons for the contrasting results could be different post-curing conditions of the specimens, different materials, different loading speed (i.e., 5 mm/s), and possibly different specimen geometry, which, however, remained unspecified. Interestingly, one of the two materials that were examined in their study was used in the present study in group 3 (i.e., Dental SG, Formlabs Inc.), which was the only group that we found to have an increased flexural modulus after being treated at 134 \({}^{\circ}\)C, in agreement with the results of [PERSON] et al. [29]. [PERSON] et al. investigated the behavior of resin materials for additive manufacturing when subjected to different temperatures (i.e., 40 \({}^{\circ}\)C, 60 \({}^{\circ}\)C, and 80 \({}^{\circ}\)C) and for varying treatment durations (i.e., 15, 30, 60, 90, and 120 min) after curing. They found that, with increasing temperature and treatment duration, the flexural modulus and Vickers hardness increased [30]. [PERSON] et al. conducted a resembling study on post-curing treatment, showing that 3D-printed aligner materials treated with higher temperatures endured higher compressive loads without deforming plastically [38]. In the present study, only two sterilization protocols were selected, and this might represent a limitation of the current study. However, the chosen protocols are among the simplest and most effective ones in dental practices and therefore are clinically relevant [39]. Another limitation is that not all the resin/printer combinations available on the market could be tested. Further, as recommended in the literature, specimens designed for mechanical testing were utilized, which is not 100% transferable to clinical settings. In addition, it has to be noted that three resins were printed with DLP, whereas only one resin was printed with SLA and SLA-LCD. It might be of interest to perform chemical analyses of the different materials before and after steam autoclaving to verify if there is any common pattern in autoclaving-induced chemical modifications.