Evaluation of fit and efficiency of CAD/CAM fabricated all-ceramic restorations based on direct and indirect digitalization: a double-blinded, randomized clinical trial

Objectives The aim of this clinical trial was to evaluate the marginal and internal fit of CAD/CAM fabricated zirconia crowns and three-unit fixed dental prostheses (FDPs) resulting from direct versus indirect digitalization. The efficiency of both methods was analyzed. Materials and methods In 25 patients, 17 single crowns and eight three-unit FDPs were fabricated with all-ceramic zirconia using CAD/CAMtechnology. Each patient underwent two different impression methods; a computer-aided impression with Lava C.O.S. (CAI) and a conventional polyether impression with Impregum pent soft (CI). The working time for each group was recorded. Before insertion, the marginal and internal fit was recorded using silicone replicas of the frameworks. Each sample was cut into four sections and evaluated at four sites (marginal gap, mid-axial wall, axio-occlusal transition, centro-occlusal site) under x64 magnification. The Mann-Whitney U test was used to detect significant differences between the two groups in terms of marginal and internal fit (alpha=0.05). Results The mean for the marginal gap was 61.08 mu m (+/- 24.77 mu m) for CAI compared with 70.40 mu m (+/- 28.87 mu m) for CI, which was a statistically significant difference. The other mean values for CAI and CI, respectively, were as follows in micrometers (+/- standard deviation): 88.27 (+/- 41.49) and 92.13 (+/- 49.87) at the mid-axial wall; 144.78 (+/- 46.23) and 155.60 (+/- 55.77) at the axio-occlusal transition; and 155.57 (49.85) and 171.51 (+/- 60.98) at the centro-occlusal site. The CAI group showed significantly lower values of internal fit at the centro-occlusal site. A quadrant scan with a computer-aided impression was 5 min 6 s more time efficient when compared with a conventional impression, and a full-arch scan was 1 min 34 s more efficient. Conclusions Although both direct and indirect digitalization facilitate the fabrication of single crowns and three-unit FDPs with clinically acceptable marginal fit, a significantly better marginal fit was noted with direct digitalization. Digital impressions are also less time-consuming for the dental practitioner and the patient. Clinical relevance The results show that a direct, intraoral, digitalized impression technique is more accurate and efficient when compared with conventional impressions in fabricating single crowns and three-unit FDPs.