Comparative in vitro study of the accuracy of impression techniques for dental implants: Direct technique with an elastomeric impression material versus intraoral scanner

BACKGROUND: The aim of this study was to compare a conventional technique (elastomeric impression material - EIM) and a digital technique (scanner digital model – SDM) on a six-analog master model (MM) to determine which was the most exact. MATERIAL AND METHODS: Twenty impressions were taken of a master model (EIM) and twenty scanned impressions (SDM) (True Definition). A coordinate measuring machine (CMM) was used to measure the distances between adjacent analogues (1-2, 2-3, 3-4, 4-5, 5-6), intermittently positioned analogues (1-4, 3-6) and the most distal (1-6). Reference values were established from the master model, which were compared with the two impression techniques. The significance level was established as 5% (p<0.05). RESULTS: The precision of each technique was compared with MM. For adjacent analogues (1-2), no significant differences were found between EIM-MM (p=0,146). For intermittently positioned analogues (1-4), SDM did not show significant differences with MM (p=0.255). For the distance between distal analogues (1-6), significant differences were found between both techniques and MM (p=0.001). CONCLUSIONS: In a clinical situation with < three implants, EIM is more exact than SDM, but in cases of four implants SDM is more exact. For rehabilitations (> four implants), neither technique can be considered accurate although error falls within the tolerance limits established in the literature (30-150µm). Key words:Digital workflow, full arch scan, intraoral scanner, CAD/CAM, polyether impression, accuracy.