Comparison of Accuracy and Timing Parameter of Digital and Conventional Impression Techniques on Fully Edentulous Jaws: an in Vivo Study

Eight consecutive patients ready for a full-arch rehabilitation on previously osseointegrated implants, and who had received an immediately loaded prosthesis, were selected. All implants had multiunit abutments placed on top. Cases from 4 to 6 implants were accepted, either upper or lower arches. Three sets of impressions were taken to each patient:

Conventional impression:

Open tray impression copings were screwed on top of all implants in the arch using a torque wrench set at 10 N/cm. Impression copings were splinted by means of Triad Gel clear resin, with an at least 3mm diameter in the resin connectors. Once the resin was photo-polymerized a cut was done in the centre of each connection with a 0.3 mm bur, to eliminate possible stress in the structure, and then it was splinted again with a drop of Triad Gel in each cut. A polyether impression was taken by means of a perforated plastic tray, and a master model was fabricated following the manufacturer's instructions. A plaster verification jig was fabricated on the model. After one week the patient came to the dental clinic where vertical dimension of occlusion was determined and the plaster key was screwed in the patient mouth to check passivity. In case the key had been fractured, a new impression would have been taken, and if not, final prosthesis could be processed.

Optical impression:

An impression of the antagonist and an impression of the edentulous arch with the healing abutments in place were taken by means of an optical scanner following the manufacturers protocol. The position of the implants was marked in the working standard tessellation language (STL) model, and the software cut a circle on top of those areas. The files were copied, and two datasets were obtained.