[Is the precision of intraoral digital impressions in orthodontics enough?]

INTRODUCTION: Replacing impression by intraoral camera is a paradigm shift. However no in vivo independent studies have compared the accuracy of analog impressions with three systems of digital impression. Are digital recordings precise enough for our orthodontic practices?

MATERIALS AND METHODS: Five impressions of the maxillary and mandibular arch of the same subject were conducted in vinylpolysiloxane, cast in plaster type IV then scanned by a laboratory scanner (VPS group). A model (maxilla and mandible) is the reference. Five scans of the maxillary and mandibular arch of the plaster model reference (group EXO) and the subject in intra-oral (INTRA group) were performed successively by the Lythos™ cameras (Ormco) version 1, iTero® (AlignTech) version 1 and TRIOS® (3shape) version 2. Numerical models of each group were cut and stacked Best Fit technique references models.

RESULTS: The images of the INTRA group have a lack of accuracy of 18 microns (p = 3.88 10-08 ) compared to images of EXO and VPS group. The maxillary arch has greater fidelity of 6 microns with respect to the mandibular arch in the three systems (p = 0.002). The fingerprinting technique (analog or digital) and the camera model - despite a difference on the number of points recorded - has no statistically significant effect on accuracy.

CONCLUSION: Carried out under ideal conditions, the accuracy of the cameras is certainly less than conventional impressions VPS but is clinically sufficient. The reduction of acquisition time may affect the accuracy, smooth out errors and get the arches contracted.