## 4 Discussion  
This study investigated whether the overall accuracy of implant positions was affected by three different additive printing technologies. The accuracy was determined by three measurements: angular deviation, 3D deviation at the entry point, and 3D deviation at the apex. Therefore, the study concluded that there were statistically significant differences among all additive printing technologies, and the null hypothesis was rejected. According to the experiment, based on the implant position, Polyjet provided the best outcome, while DLP and SLA reported diminished accuracy. For the entry point and apical deviations, the result did not align with [PERSON]'s study [18], which claimed that there was no statistically significant difference among all 3D printers. The reason for this might be due to the different types of 3D printing technologies, which were SLA, Polyjet, and Multijet. Although the mean deviation of the angle was not different between all technologies, the result was consistent with a recent study [18]. The finding also suggested that the angular deviation might be less sensitive to printing technologies. The angular deviations from Polyjet, DLP, and SLA were within the range of clinical acceptability, based on the recent systematic review [19; 20; 21]. Overall, these findings are in accordance with a recently published study, which investigated the trueness and precision of surgical guides between Polylet, DLP, SLA, and FFF (fused filament fabrication). The trueness of Polylet outperformed that of SLA and DLP and in the aspect of precision, the performance of Polylet surpassed SLA [3]. On the contrary, the processing time of DLP technology, which is another critical factor in choosing 3D printers, was by far the shortest, compared to Polylet and SLA. In general, every step in the workflow of implant-guided surgery carried a margin of inaccuracy [15]. Several factors influence the accuracy of the static guided implant surgery such as study design, surgical guide design, type of guided surgery, implant characteristics, operator's experience, and printing technique. This study, therefore, minimized the overall effect of confounding factors as much as possible through various techniques. To minimize confounding factors, we utilized the same guide design, drill protocol, surgeon, and type of surgical models. The implant placement using different printed guides was also done at random to reduce the drilling memorization of the surgeon. Considering the study design, this study was performed in vitro aspect. This method appeared to be the most reliable compared to in vivo and cadaver studies because the models provided clinicians with better accessibility and visualization. Besides, the advantage of an in vitro study compared to an in vivo one was the absence of patient movement, saliva, or blood [19]. Additionally, for surgical guide design, this experiment used tooth-support surgical guides, which showed less deviation of implant position compared with those supported by the bone and by mucosa, in all aspects of the entry point, apex point, depth, and angulation [19; 22; 23; 24; 25; 26; 27; 28]. Next, another vital factor is that the type of guided surgery can give rise to the deviation. When there are sufficient bone and keratinized mucosa, fully guided surgery is the most precise approach for flapless surgery, which can decrease chair time, compared to a free-handed approach [11; 29; 30] or pilot-drill, half-guided surgery [11; 29; 30; 31; 32]. Additionally, these studies performed fully guided surgery to maximize accuracy. Moreover, implant characteristic is an important factor \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Printer** & **DLP** & **Polylet** & **SLA** \\ \hline Printing time (min) & 22 & 248 & 337 \\ Post-processing time (min) & 23 & 7 & 16 \\ Total (min) & 45 & 255 & 353 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The comparison of processing and post-processing time among DLP, Polylet, and SLA 3D printers. influencing the accuracy. [PERSON] et al.