Accuracy of intraoral digital impressions using an artificial landmark

Statement of problem. Intraoral scanners have been reported to have limited accuracy in edentulous areas. Large amounts of mobile tissue and the lack of obvious anatomic landmarks make it difficult to acquire a precise digital impression of an edentulous area with an intraoral scanner. Purpose. The purpose of this in vitro study was to determine the effect of an artificial landmark on a long edentulous space on the accuracy outcomes of intraoral digital impressions. Material and methods. A mandibular model containing 4 prepared teeth and an edentulous space of 26 mm in length was used. A blue-light light-emitting diode tabletop scanner was used as a control scanner, and 3 intraoral scanners were used as experimental groups. Five scans were made using each intraoral scanner without an artificial landmark, and another 5 scans were performed after application of an artificial landmark (a 4x3 mm alumina material) on the edentulous area. The obtained datasets were used to evaluate trueness and precision. Results. Without an artificial landmark on the edentulous area, the mean trueness for the intraoral scanner ranged from 36.1 to 38.8 mu m and the mean precision ranged from 13.0 to 43.6 mu m. With an artificial landmark on the edentulous area, accuracy was improved significantly: the mean trueness was 26.7 to 31.8 mu m, and the mean precision was 9.2 to 12.4 mu m. Conclusions. The use of an alumina artificial landmark in an edentulous space improved the trueness and precision of the intraoral scanners tested.