## 4 Discussion
investigated the effect of these storage environmental conditions on the accuracy of 3D-printed models, determining that there were no statistically significant differences between environments with a temperature of 4 \(\pm\) 1 or 20 \(\pm\) 2 degrees Celsius [35]. Based on these results, the models of the present study were stored at a controlled temperature of 20 \(\pm\) 2 degrees Celsius to prevent this factor from affecting the final accuracy of the models. In addition, [PERSON] et al. also analyzed the impact of time on the accuracy of the models printed with AM technology, concluding that the dental models should not be used longer than 3 or 4 weeks after being manufactured [36]. Based on these results, the models in the present study were printed and stored until the complete sample was obtained, not exceeding two weeks between printing and digitalization, so this parameter would not interfere with the results. The post-processing methods can also affect the performance of the printed samples, as the resins used suffer shrinkage and deformation [37; 38; 39; 40]. In the present study, this process followed the manufacturer's instructions. It has also been noticed that this parameter can be reduced by increasing the photopolymerizing time or using microwave or UV radiation. It is also noteworthy that previous studies determined that building orientation also affects the mechanical properties of the printed specimens, affecting the passivity of the implant prostheses, establishing that models printed horizontally were the most affected. This conclusion agrees with the results obtained in the present study, where the best accuracy was reported in the 45-degrees group [13; 41]. Previous studies have evaluated the impact of printing orientations. [PERSON] et al. [30] used an SLA printer to print surgical splints, obtaining greater precision in the 0- and 45-degrees groups than in the 90-degrees group, so their results agreed with those obtained in the present study. However, [PERSON] et al. evaluated the fabrication of complete prosthetic bases with DLP and SLA and found that the 90-degrees angulation provided greater trueness in both types of printers [31]. These differences may be explained by the printer models used, the geometry of the printed object, and the material used. In tooth-supported crowns, the best accuracy was found at a 135-degree printing orientation [42]. This corresponds to an angulation of 45 degrees, coinciding with the most accurate impression angulation in the case of the present study. Other studies have also reported ranges between 30 and 90 degrees as the most accurate groups, depending on the printers used [43]. The evidence about the influence of the printing parameters in the accuracy of 3D implant printed models is limited. In addition, it is worth noting that the 90-degree printing orientation allows for the manufacturing of more models simultaneously, which decreases the overall printing time of the specimens. An increase in print layers leads to an increase in printing time and possibly a higher probability of failure [44; 45], so the 90-degree printing orientation also decreases resin waste by reducing the extent of the layers. In the present study, two modelsper print run were used in all study groups until the sample size was complete so that this parameter did not influence the study's final results. Discrepancies between groups may be due to multiple factors in addition to the printing orientation, such as the build starting points [46] or the scanner employed in digitizing the models [47; 48]. Additionally, analog and scan body designs can affect the results. Further research focused on studying the influence of the different analog designs and materials would be recommendable. The clinical application of the present study can be translated into a better fit of the implant-supported prostheses. There is currently no consensus among clinicians on the magnitude considered \"unacceptable\", as the data found in the literature varies up to 150 \(\upmu\)m [39].