A research report submitted to the School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Dentistry in the branch of Prosthodontics Johannesburg, 2017 / Purpose: To perform a comparative analysis of the accuracy of intra-oral and extra-oral digital scanners when used for the milling of a long-span implant supported superstructure framework. Method: Three intra-oral and three extra-oral scanners were used to measure a master model containing five implant analogues. The three-dimension positions of the implant analogues were measured with a coordinate measuring machine. The digital data from the scanners were used to mill the implant positions in aluminium blanks from a single milling device. These implant positions were measured at the same points as the master model. The three-dimensional differences were calculated to provide a measure of the most accurate frameworks. Results: For the intra-oral scanners, the further the measurement between points, the greater the standard deviation (the poorer the precision) and the poorer the mean accuracy. However, these were clinically acceptable over short distances. For the extra-oral scanners, there was no correlation between the length of the measured distances and the accuracy of the produced framework. All the extra-oral scanners were clinically acceptable for complete-arch prostheses. Conclusions: Noting the limitations of this study and the use of a milling centre to mill the frameworks, for the intra-oral scanners, the 3Shape Trios® (3Shape, Copenhagen, Denmark) can be used for measurements up to 21,5mm and the Sirona CEREC OmniCam (Sirona Dental Systems, Inc., Bensheim, Germany) can be used for measurements up to 34mm. The extra-oral scanners used in this study can be used for complete-arch implant prosthetics. The accuracy of these is relative to the model or impression created. Steps should therefore be made to ensure the accuracy of the model such as the use of a verification jig / MT2017