الفهرس 
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Abstract
This study aimed to compare the fit of monolithic multilayer zirconia FPDs produced using conventional and digital impressions and to assess the trueness and precision of both techniques and their significance on the fit results.
Twelve participants with missing upper first premolar received preparations for zirconia FPDs. Two impressions were taken for each patient: a digital impression with CS 3500 intraoral scanner (group D), and a conventional one-step polyether impression (group C). Two monolithic zirconia FPDs were fabricated for each patient, and the marginal and internal fit of the restorations were assessed using the internal replica technique. For trueness and precision assessment, five digital impressions were taken for a master model using CS 3500 and saved as an STL file format. Five conventional impressions were taken with polyether impression material, poured with type IV dental stone, and scanned with an extra-oral scanner. The obtained data were saved as an STL file format. A 3D matching software was used to analyze STL data obtained from both impression techniques qualitatively and quantitatively). The deviations were measured and averaged to obtain the values of trueness and precision. group D resulted in a significantly better marginal and internal fit. However, the mean values of trueness and precision for conventional and digital techniques were comparable.
Available studies comparing fit accuracy of zirconia fixed partial dentures fabricated from conventional impressions and digital scans provide contradictory results. In addition, studies have been heterogeneous and of a limited number to provide conclusive evidence. A systematic review and meta-analysis were to compare the marginal and intaglio fit of tooth-supported zirconia FPDs fabricated from conventional impressions and digital scans and to investigate the effect of different variables on the fit results. An electronic search was performed on the National Library of Medicine (NLM), Cochrane Central Register of Controlled Trials, and Scopus databases. In addition, a manual search was carried out. Studies comparing the fit of tooth-supported zirconia FPDs fabricated from conventional impressions and digital scans and reporting sufficient data for qualitative and quantitative analysis were included. Standard mean differences (SMDs) and 95% confidence intervals (CI) were calculated for meta-analysis. Subgroup analysis was performed to study the effect of variables including restoration form (monolithic or framework), units number, intraoral scanner (IOS) type, conventional impression material, spacer thickness, and abutments region.
Digital scan displayed significantly better marginal fit. Test for subgroup difference showed a significant influence of only impression material type and units number on marginal fit.