In dentistry, 3D IOS (intra-oral scanners) are gaining an increasing popularity essentially for the production of dental prostheses. Until now, there is no normalized procedure to determine the resolution of IOS. Such a procedure could be a positive parameter for the IOS market and a first step in their normalization. The aim of this study is to present a reproducible methodology to estimate the noise and resolution of any type of IOS. For the noise, we used the IOS Trios 2 (3Shape) and the Carestream 3500 (Carestream) for noise and resolution. As reference, we used an ultra-flat and ultra-smooth alumina. Being perfectly flat, any record of roughness should be interpreted as noise. In this study, the root mean square (RMS) values obtained are ranged between 5.29 and 12.58 micrometers. Significant differences have been found between the central part and the whole mesh. This is due to edge effect: deviation from a flat surface is more important on the edge of meshes than the internal part. To evaluate the resolution, a ceramic tip, well-polished was recorded with the IOS’s and compared to the mesh obtained with micro tomography (5 micrometer resolution). We measured the distance between the two plans of the tip, considered as the small detail recorded. We found a distance from 89 to 121 micrometers with IOS studied and 25 micrometers with micro CT. Those methods, simple and reproducible, could be perfectly suitable to evaluate and compare commercial all types of IOS’s.