Crown Accuracy and Time Efficiency of Cement-Retained Implant-Supported Restorations in a Complete Digital Workflow: A Randomized Control Trial

Purpose This is a clinical study to compare complete digital workflows generated using intraoral scanning and the split-file technique with a conventional workflow for cement-retained implant-supported restorations. Materials and methods Forty patients requiring posterior single-unit implant restorations were included. Twenty patients were randomly assigned to the complete digital workflow group, involving intraoral scanning and manufacture of cement-retained crowns using the split-file technique (test group). The remaining 20 patients were assigned to the hybrid workflow group (control group), involving conventional impressions and CAD/CAM-fabricated crowns based on stone casts. Scanning of the crowns was performed before and after clinical adjustment using an intraoral scanner (TRIOS Color; 3Shape). Two 3D digital models were trimmed and superimposed to evaluate changes in dimensions using Geomagic Control 2014 software. Chair-side and laboratory times for the entire workflow were recorded. Independent-sample t tests were used for the statistical analysis. Results All crowns were inserted without re-fabrication. The average maximum occlusal adjustment of the crowns, measured as maximum deviation of occlusal area in superimposed pre and post scans, was -212.7 ±150.5 and -330.7 ±192.5 μm in the test and control groups, respectively (p = 0.037).The average area of occlusal adjustment, measured as area of deviation larger than 100 μm, was 8.4 ±8.1 and 17.1 ±12.3 mm2 in the test and control groups, respectively (p = 0.012). The mesial and distal contact adjustment amounts, maximum deviations of proximal area, were -33.0 ±96.2 and -48.6 ±70.5 μm in the test group, and -3.7 ±66.7 μm and -11.4 ±106.7 μm in the control group, respectively. The mean chair-side time was 20.20 ± 3.00 and 26.65 ± 4.53 min in the test and control groups, respectively (p Conclusions Single-unit cement-retained crowns with complete digital workflows required fewer crown adjustments and had shorter clinical and laboratory times compared to conventional impressions and hybrid workflows. Digital impressions and the split-file technique provided customized abutments and cement-retained crowns, thus broadening the indications for digital workflows for implants. This article is protected by copyright. All rights reserved.