## 4 Discussion
investigated the influence of macrodesign on precision. The tapered macrodesign (BLT) offered greater accuracy compared to parallel-walled macro designs (TL,BL), owing to the geometric insertion, the drill design, and the thread design [33]. As a consequence, an implant with a tapered design (BLT) was used in this research to minimize deviation. Another related factor is the experience of an operator. A study reported that the difference between angular and linear deviations was not statistically significant between experienced and inexperienced surgeons, yet it is better to experiment with the experienced surgeon to avoid the confounding factor for this study [34]. In another study, they evaluated whether the deviation of the static surgical guide was affected by the type and number of teeth supporting the surgical guide. The accuracy of surgical guides, supported by four teeth which can decrease cost and processing time, was not different to that of full-arch-supported guides. However, to lessen the error from the external factor, this study used the full-arch-supported guides [35]. Lastly, regarding the printing technique, there was no statistically significant difference in implant position between a surgical guide manufactured by the additive technique \"3D printing\" and the subtractive technique \"milling\". Nevertheless, while producing comparable accuracy for implant guided surgery, the surgical guide fabricated by 3D printers could be a substitution due to the ease of production and the diminution of laboratory time and materials, consequently increasing cost-effectiveness [36]. However, the deviation of the implant position can be affected by the surgical procedure. To begin with, the surgical guides were not designed for an individual model but rather were designed based on a randomly selected model. Apart from the surgical procedure, due to the roughness surface of the sleeve or resin interface as well as the offset setting, the placing of the guide sleeve into the surgical guide probably contributed to another aspect affecting the implant deviation. Moreover, differences in post-processing recommendations and instruments may have an influence on the surface of the surgical guide [37]. Although, with quality control such as caliper and weight measurements, the models may not perfectly replicate bone properties including strength, elasticity, hardness, and density. Additionally, the print quality can be enhanced to improve the correctness of the study. A 3D printer resolution is an important indicator to determine the printing quality and is directly associated with the layer thickness. Specifically, the layer of thickness can affect 3D smoothness significantly. The thinner the layer is, the smoother 3D prints become. With the greater thickness of the layer, it was observed that the surface of a printed layer was rough, as each layer was easily noticeable. Furthermore, the recent study also suggested that the effect of layer thickness can result in the deviation of the intaglio dimension of the surgical guide [37]. Ultimately, an in vitro study might not truly reflect the error of implant position performed in a clinical trial. The deviation in an in vitro study might be relatively marginal, and accordingly can be neglected in a clinical trial. Thus, there should be a further study conducting a clinical trial to illustrate the true potential of each 3D printer. Lastly, human errors should also be taken into consideration. On the whole, to make the final decision on choosing a 3D printer for fabricating surgical guides, apart from the printer's accuracy and processing time, additional factors such as price, operating cost, maintenance cost, and after-sales service should all be taken into account.