Fit of zirconia fixed partial dentures fabricated from conventional impressions and digital scans: A systematic review and meta-analysis

Abstract

Statement of problem: Available studies comparing fit accuracy of zirconia fixed partial dentures (FPDs) 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.

Purpose: The purpose of this systematic review and meta-analysis was 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.

Material and methods: 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.

Results: The initial search resulted in a total of 608 articles. Nine articles were included in the analysis (1 clinical and 8 in vitro) evaluating 118 restorations. Digital scan displayed significantly better marginal fit (P<.001; SMD: -0.68; 95% CI: -0.92, -0.09) and intaglio fit (P=.020; SMD: -0.51; 95% CI: -0.94, -0.42). Test for subgroup difference showed a significant influence of only impression material type (P=.008) and units number (P=.030) on marginal fit. Digital scan showed significantly better marginal accuracy for 3-unit FPDs than 4-unit FPDs (P<.001; SMD: -1.02; 95% CI: -1.41, -0.63). In addition, digital scanning had significantly better marginal fit with polyvinyl siloxane than polyether (P<.001; SMD: -0.98; 95% CI: -1.32, -0.64). A cement spacer ≤50 μm improved both marginal and intaglio fit in the digital group. The TRIOS scanner resulted in the best performance in the digital group for marginal fit.

Conclusions: Digital scanning provides significantly better marginal and intaglio fit than conventional impression making for fabricating zirconia FPDs up to 4 units, either in monolithic form or frameworks and at any region of the arch. However, further clinical studies are recommended to obtain more substantial results.