## 4 Discussion  
In this study, we aimed to compare the marginal fit of fixed dental restorations fabricated with the provisional prosthesis scanning technique versus a conventional impression technique and to determine the effect of both variables on the accuracy outcome. Achieving passive fit of implant prosthesis is a key factor in the long-term success of treatment [3; 19]. Our study showed that the fit of metal frameworks fabricated with the provisional prosthesis scanning technique was significantly more accurate than those fabricated with the conventional impression open-tray technique. The results of a few previous studies have demonstrated superior accuracy, in terms of trueness and precision of fully digital impressions for full-arch restorations as compared with those of conventional techniques [30; 31; 32; 33; 34; 35]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **CIG** & **PPSG** & **Mann–Whitney** \\  & **Mean \(\pm\) SM** & **Mean \(\pm\) SM** & **Test** \\ \hline
**Marginal fit discrepancy (um)** & 170 \(\pm\) 50 & 1080 \(\pm\) 40 & \(p\) \(<\) 0.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Marginal fit discrepancy between the conventional impression group (CIG) and provisional prosthesis scanning group (PPSG). Figure 10: Laboratory tools that facilitate the bonding process to keep the cylinder access holes open. Our results are in agreement with those by [PERSON] et al. [36] who reported that the mean vertical fit discrepancy of a prosthesis with a fully digital workflow was 169 \(\upmu\)m.  
Clinical studies have reported that an acceptable fit discrepancy is within the range from 100 to 200 \(\upmu\)m [16; 37; 38]. According to [PERSON] et al. [36], a fit discrepancy \(<\) 200 \(\upmu\)m was considered to be clinically acceptable. The results of the present study lie within these ranges for the provisional prosthesis scanning group, while those of the conventional impression group lie outside the reported ranges of the acceptable misfit. The above-mentioned findings highlight the potential advantages of the so-called complete digital workflow. Impression accuracy and the fit of the definitive prosthesis depend on the phases of the process. Various factors can contribute to a misfit of the final prosthesis, such as the accuracy of implant impression, master cast fabrication, and prosthesis fabrication procedures [39].In conventional techniques, each step (connection of impression copings, obtaining impression, connection of implant analogs, mechanical tolerance in each step, creating a stone cast, scanning, merging process, designing, and milling) has its own errors, and accumulating all of these has a significant effect on the accuracy of the final fit [2; 3; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41]. In contrast, the provisional prosthesis scanning technique requires fewer steps (i.e., creating provisional prosthesis, scanning, designing, and milling); consequently, the number of error sources is fewer as compared with the conventional techniques [3; 40; 41]. This can explain the significant marginal fit discrepancy between these two methods in our study. Understanding the impact of these factors helps to ensure the fabrication of an accurate master cast, which reduces the risk of framework misfit. Using fully digital workflow minimizes complications associated with framework misfit. In the present study, a relatively high variation of precision in the provisional prosthesis scanning group can be caused by cylinder displacement. One of the common reasons is cylinder damage which can occur during the prosthesis polishing process. To eliminate its effect on the final prosthesis accuracy, the cylinder base should be protected using polishing caps during the polishing process. Another key factor that hinders the full sitting of cylinders is an ill-fitting prosthesis screw access hole with cylinders connected to the implant during the bonding process.