Crown adjustment and chairside efficiency of single-unit restorations fabricated from immediate and staged...

This is a clinical study to compare immediate and staged impression methods in a complete digital workflow for single-unit implants in the posterior area.

Sixty patients requiring single-unit implant crowns were enrolled. Forty patients were assigned to the test group, immediate digital impression after implant surgery with crown delivery 4 months later. The remaining 20 patients were assigned to the control group, staged digital impressions 4 months after implant surgery, and crown delivery 1 month later. Both workflows involved free-model CAD-CAM crown fabrications. The crowns were scanned before and after clinical adjustment using an intraoral scanner (TRIOS Color; 3Shape). Two 3D digital models were trimmed and superimposed to evaluate the dimensional changes using Geomagic Control software. Chairside times for the entire workflow were recorded. Kruskal-Wallis was performed to compare crown adjustments between two groups, while One-way ANOVA was used to compare chairside time durations between the test and control groups.

All crowns were delivered without refabrication. The average maximum occlusion adjustment of crowns was -353.2 ± 207.1 μm in the test group and -212.7 ± 150.5 μm in the control group (p = 0.02). The average area of occlusal adjustment, measured as an area of deviation larger than 100 μm, was 14.8 ± 15.3 and 8.4 ± 8.1 mm² in the test and control groups, respectively (p = 0.056). There were no significant differences in the mesial and distal contact adjustment amounts, or the maximum deviations of the proximal area, between the two groups. The mean chair-side time was 50.25 ± 13.48 and 51.20 ± 5.34 min in the test and control groups, respectively (p = 0.763).

The immediate impression method in the digital workflow for single-unit implants required more occlusal adjustments of crowns but showed similar chairside times compared to the staged impression method.