Comparison of marginal and internal fit of 5-unit monolithic zirconia fixed dental prostheses made with direct and indirect digitalization: An in vitro study

Digital impressions has been widely used in the manufacturing of indirect restorations. However, the limited number of studies examined the accuracy of the digital scanners in the production of multi-unit restorations. The aim of this in vitro study was to evaluate the marginal and internal discrepancy of 5-unit monolithic zirconia bridges made via direct and indirect digitalization with three-dimensional replica method and optical digitization. A phantom model was designed that mimic the missing of the maxillary lateral and first premolar. Maxillary right central, canine, second premolar were prepared. The reference model was scanned with 3Shape Trios 3 and CEREC Omnicam intraoral scanners for direct digitalization (3S-IOS, C-IOS) and conventional impressions were taken for indirect digitalization with polyvinyl siloxane impression material. The impressions were scanned with 3Shape E3 and CEREC InEosX5 laboratory scanners (3S-IMP, C-IMP). The impressions were then poured, and the stone casts were scanned with same laboratory scanners (3S-CAST, C-CAST). After the digitalization, 5-unit zirconia bridges were manufactured with CAD-CAM (n=10). Marginal and internal discrepancy of the restorations were evaluated with three-dimensional replica method and optical digitization (ATOS Triple Scan). The results were compared using Kruskal-Wallis analysis of variance. No statistically significant difference was observed between the marginal and internal discrepancy of restorations produced using intraoral scanners (p>0.05). The restorations manufactured with direct and indirect digitalization, did not reveal a statistically significant difference (p>0.05). For indirect digitalization group, impression scan and stone cast scan techniques showed similar results (p>0.05). The marginal and internal discrepancy of 5-unit restorations manufactured with direct and indirect techniques were similar and within the acceptable clinical limits. (<120 µm). Key Words: multi-unit, zirconia, intraoral scanner, extraoral scanner, marginal discrepancy