The technological advances in the field of dentistry by virtue has made dentists take a great shift from manual methods of diagnosis and treatment to digitally aided diagnosis, treatment planning, and prosthesis fabrication, therefore, increasing the need to assess the efficiency and efficacy of the digital equipment and software to obtain higher accurate results. Intraoral scanners (IOS) or laboratory model scanners form the basis of a CAD CAM fabrication because intra-oral / model scanning is the only way to digitize the oral environment. Identify the accuracy of IOS under the influence of various intra-oral and extra-oral factors. Advanced tools in the Cochrane and PUBMED database were used for the systematic search for a structured search and a hand search was done in the Google scholar database. 37 articles were included in the systematic review based on selected criteria. There were more in vitro studies on the evaluation of the accuracy of intra-oral scanners under influence of clinical and extraoral variables than in vivo studies. The studies reviewed showed a variety of variables and outcomes related to the accuracy of the IOS. Several extra-oral and intra-oral factors had a significant difference in terms of trueness and precision when compared between different intra-oral systems. The factors also had an impact on the efficiency of the intra-oral scanners. Though intraoral scanners are said to have comparable results to conventional techniques it is still vulnerable to inaccuracies due to several intraoral and extra-oral variables.