## 4 Discussion
Two studies, [PERSON] et al. (2019) and [PERSON] et al. (2020), identified that post-washing with different cleaning products can significantly influence dimensional accuracy due to improper removal of uncured resin monomer leading to high surface roughness and a reduced degree of conversion. These studies compared different post-washing solutions and found that the manufacturer's recommendation did not always provide the highest mechanical properties. Both studies used a DLP printer and a resin containing 7,7,9(or 7,9,9)-trimethyl-4,13-diox-3,14-diox-5,12-diazhexadecane-1,16-diylbismethacrylate, and found that cleaning with 100% isopropanol (as per the manufacturer's recommendation) resulted in the second highest degree of conversion (%) of 90.8 \(\pm\) 4.5, whilst using Yellow Magic 7 cleaner resulted in 93.4 \(\pm\) 1.6%. Further research should explore using different cleaning media that may veer from the manufacturer's guidelines to obtain the highest dimensional accuracy. Some limitations to consider include operator error. In this study, to reduce inter-operator variability and inconsistency, a single operator performed the surgical guide printing and washing, J.K.L., while a second operator performed the surgical guide post-curing, W.L. Hence, while precision in the form of repeatability was assessed, the same cannot be claimed for reproducibility amongst different operators. The operators' training and experience has been reported to influence post-processing ([PERSON] et al., 2019). This study also only investigated the accuracy of the drill holes. The presence of soft and hard tissue interferences, saliva, blood, and patient movement may impact the surgical guide's seating, site preparation, and implant insertion, factors that have not been investigated in this in vitro study. Moreover, other factors may influence the accuracy of surgical guides and need to be considered that are out of the scope of this study. A limitation of this study is assessing the possible effects of disinfection and sterilisation on the accuracy of 3 DP implant surgical guides. The last step of preparing the surgical guides prior to patient use, where there is contact with the oral cavity, is disinfection and sterilisation, as without proper protocols, there is chance of infection ([PERSON] et al., 2019). Sterilisation involves the complete removal and destruction of all microbial organisms, whilst disinfection removes any microbial organisms that produce spores ([PERSON] et al., 2019), and both have been found to significantly impact the properties of surgical guides, with heat sterilisation at 121 and 134 \({}^{\circ}\)C modifying the mechanical properties of DLP and SLA 3 DP guides, when compared to disinfection with 4% aldehyde-free disinfect ([PERSON] et al., 2019). Previous studies identified a statistically significant difference between SLA and DLP printers, with DLP demonstrating a lower deviation at the entry point of the implants (\(p\) = 0.023) and proving to be more accurate ([PERSON] et al., 2019). Assessing different types of 3D printers, such as SLA printers, for dimensional stability might be helpful for future studies to account for manufacturing errors arising from the printing system. Further research should also be aimed at assessing dimensional stability in an intra-oral environment as well as the impact of storage time, which are out of the scope of this in vitro study.