Technological advances in dentistry have led to a significant shift from traditional diagnostic and therapeutic approaches to digital techniques, including digital diagnosis, treatment planning, and prosthesis manufacturing. This transition has heightened the need to evaluate the performance and precision of digital tools and software to achieve more accurate outcomes. Intraoral scanners (IOS) and laboratory model scanners are essential in CAD CAM fabrication, as they are the only means to digitally record the oral environment. The accuracy of IOS is affected by various intra-oral and extra-oral factors. This review aims to investigate the factors that affect the accuracy of intra-oral scanners. A systematic review was conducted using advanced search tools in the PubMed and Cochrane databases, supplemented by a manual search in Google Scholar. A total of 37 studies met the inclusion criteria for the review. Most studies focused on the in vitro evaluation of IOS accuracy under the influence of clinical and extra-oral variables, with fewer in vivo studies. The results showed that multiple factors significantly affected both the trueness and precision of different intra-oral scanning systems, impacting their overall efficiency. While intraoral scanners provide comparable results to conventional methods, they remain susceptible to inaccuracies because of the influence of various intra-oral and extra-oral factors.
