Digital evaluation of the dimensional accuracy of four different implant impression techniques

The aim of this study was to compare the dimensional accuracy of four different implant impression techniques of a mandibular edentulous model with five parallel implants.

Five dental implants were placed in an edentulous mandibular model in parallel. A total of forty impressions were obtained using four different impression techniques. In Group 1 (G1) and Group 2 (G2), closed tray impressions with and without plastic caps, respectively, were used. In Group 3 (G3) and Group 4 (G4), open tray impressions with a direct splinted technique and an improved direct splinted technique, respectively, were used. All the impressions were poured with Type IV dental stone. Master model and study casts were scanned with a laser optical scanner and aligned by observing the superpositions of the anatomical landmarks using a software program.

Fifty measurements of the apical, coronal, and angular discrepancies of the master and study casts were obtained (n = 50) and statistically analyzed using a one-way analysis of variance and post hoc (least significant difference ) and Friedman's tests.

The lowest accuracy was obtained from G2 when the angular (1.48°), coronal (0.32 μm), and apical (0.14 μm) deviations were tested (P < 0.05), whereas no statistically significant differences were found among the other groups (P < 0.05).

In cases with five parallel mandibular implants, improved accuracy was achieved using the direct splinted technique, the improved direct splinted technique, or the closed tray impression technique with snap on plastic caps.