Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part II: CAD-CAM versus conventional laboratory procedures

STATEMENT OF PROBLEM Clinical studies are needed to evaluate the entire digital and conventional workflows in prosthetic dentistry. PURPOSE The purpose of the second part of this clinical study was to compare the laboratory production time for tooth-supported single crowns made with 4 different digital workflows and 1 conventional workflow and to compare these crowns clinically. MATERIAL AND METHODS For each of 10 participants, a monolithic crown was fabricated in lithium disilicate-reinforced glass ceramic (IPS e.max CAD). The computer-aided design and computer-aided manufacturing (CAD-CAM) systems were Lava C.O.S. CAD software and centralized CAM (group L), Cares CAD software and centralized CAM (group iT), Cerec Connect CAD software and lab side CAM (group CiL), and Cerec Connect CAD software with centralized CAM (group CiD). The conventional fabrication (group K) included a wax pattern of the crown and heat pressing according to the lost-wax technique (IPS e.max Press). The time for the fabrication of the casts and the crowns was recorded. Subsequently, the crowns were clinically evaluated and the corresponding treatment times were recorded. The Paired Wilcoxon test with the Bonferroni correction was applied to detect differences among treatment groups (α=.05). RESULTS The total mean (±standard deviation) active working time for the dental technician was 88 ±6 minutes in group L, 74 ±12 minutes in group iT, 74 ±5 minutes in group CiL, 92 ±8 minutes in group CiD, and 148 ±11 minutes in group K. The dental technician spent significantly more working time for the conventional workflow than for the digital workflows (P.05). CONCLUSIONS Irrespective of the CAD-CAM system, the overall laboratory working time for a digital workflow was significantly shorter than for the conventional workflow, since the dental technician needed less active working time