## 4 Discussion
However, the reduction in fracture strength for CM and AM restorations was not statistically significant, possibly because autopolymerization continued beyond the initial setting, thereby mitigating some of the detrimental effects of water absorption and hydrolysis. Repeated thermal expansion and contraction may also have facilitated molecular rearrangement within the resin. In contrast, the blocks used for the SM technique are fully polymerized and, thus, do not benefit from any residual polymerization effect [7; 25]. These observations further suggest that the larger volume of fixed partial dentures, which requires a longer auto-polymerization time, could contribute to the differences observed in temporary crowns and fixed partial dentures. In a systematic review, it was concluded that AM-printed provisional crowns and FDPs could be considered alternatives to those manufactured by CM and SM methods for long-term provisional use [4]. In this study, as the restorations transitioned from single-unit to multi-unit designs after aging, the differences between manufacturing methods were no longer statistically significant. Therefore, the substantial decrease observed in SM fixed partial dentures post-aging raises concerns about their long-term clinical viability, despite their advantages for long-span interim treatments. [PERSON] et al. [2] contributed further insight by comparing the techniques of CM, SM, and AM for temporary crown restorations. They reported that SM and AM restorations exhibited higher fracture strength values than CM restorations. This difference may be attributed to the operator-dependent nature of the conventional method. The literature has demonstrated that conventional temporary restoration is technique- and experience-sensitive, and its mechanical properties may be influenced by the operator's skill and experience, with potential manipulation errors impacting the outcomes [32]. [PERSON] et al. [19] also reported that temporary crowns fabricated using the AM technique exhibited significantly higher fracture resistance than those produced with the SM technique. However, a vertical printing orientation with supports on the buccal surface was applied in their study, whereas a 0-degree orientation with occlusal supports was used in the present study. Previous studies have shown that mechanical properties (e.g., wear volume, fracture load, flexural strength, and tensile strength) are generally superior in resin that is printed at a 0-degree orientation [39; 40; 41]. Accordingly, this orientation was selected, as the applied load remains perpendicular to the printing layer direction, potentially enhancing the strength of the printed object. Each printed layer is also thought to act as a barrier against complete fracture because a crack must propagate sequentially through each layer until failure occurs. Removing the occlusal supports, however, may induce microcracks and compromise fracture resistance in this region [1]. In addition, the lower fracture resistance values for Telio CAD (PMMA block), as observed by [PERSON] et al. [19], may be attributable to a more aggressive aging protocol. The added effect of mechanical aging could further weaken the material by promoting microcrack formation [42]. Similarly, [PERSON] et al. [25] reported that the AM technique exhibited the highest fracture strength values for temporary crown restorations, with no significant difference observed between the AM and SM techniques. In their study, crowns were produced using a 100 \(\upmu\)m layer thickness and a 90-degree printing orientation. A lower layer thickness, however, has been associated with an increased number of layer-to-layer interfaces, which enhance polymerization and can positively influence mechanical performance [43]. In the present study, specimens were printed at a 50 \(\upmu\)m layer thickness, and the use of different materials may also have contributed to variations in the outcomes.