Randomized controlled clinical trial of digital and conventional workflows for the fabrication of zirconia-ceramic fixed partial dentures. Part III: Marginal and internal fit

Statement of problem. Trials comparing the overall performances of digital and conventional workflows in restorative dentistry are lacking. Purpose. The purpose of the third part of this clinical study was to test whether the fit of zirconia 3-unit frameworks for fixed partial dentures fabricated with fully digital workflows differed from that of metal frameworks fabricated with the conventional workflow. Materials and methods. In each of 10 participants, 4 fixed-partial-denture frameworks were fabricated for the same abutment teeth according to a randomly generated sequence. Digital workflows were applied for the fabrication of 3 zirconia frameworks with Lava, iTero, and Cerec infiniDent systems. The conventional workflow included a polyether impression, manual waxing, the lost-wax technique, and the casting of a metal framework. The discrepancies between the frameworks and the abutment teeth were registered using the replica technique with polyvinyl siloxane. The dimensions of the marginal discrepancy (Discrepancy(marginal)) and the internal discrepancy in 4 different regions of interest (Discrepancy(shoulder), Discrepancy(axial), Discrepancy(cusp), and Discrepancy(occlusal)) were assessed using a light microscope. Post hoc t tests with Bonferroni correction were applied to detect differences (alpha=.05). Results. Discrepancy(shoulder) was 96.1 +/- 61.7 mu m for the iTero, 106.9 +/- 96.0 mu m for the Lava, 112.2 +/- 76.7 mu m for the Cerec infiniDent, and 126.5 +/- 91.0 mu m for the conventional workflow. The difference between the iTero and the conventional workflow was statistically significant (P=.029). Discrepancyo(cclusal) was 153.5 +/- 66.8 mu m for the iTero, 203.3 +/- 127.9 mu m for the Lava, 179.7 +/- 63.1 mu m for the Cerec infiniDent, and 148.8 +/- 66.8 tm for the conventional workflow. occlusal Discrepancy was significantly lower for the conventional workflow than for the Lava and the Cerec infindent workflows (P<.01). The iTero resulted in significantly lower values of Discrepancy(occlusal) than the Lava and the Cerec infiniDent workflows (P<.01). Conclusion. In terms of framework fit in the region of the shoulder, digitally fabricated zirconia 3-unit frameworks presented similar or better fit than the conventionally fabricated metal frameworks. In the occlusal regions, the conventionally fabricated metal frameworks achieved a more favorable fit than the CAD-CAM zirconia frameworks.