Comparative analyses of accuracy between digital and conventional impressions for complete-arch implant-supported...

To compare the three-dimensional (3D) accuracy of digital (intraoral scanning and photogrammetry) and conventional implant impressions for complete-arch implant-supported fixed dental prostheses.

A systematic search was conducted in electronic databases using relevant MeSH keywords to identify in vitro and in vivo studies comparing the 3D accuracy of digital versus conventional implant impressions. Eligible studies were included in a meta-analysis, with subgroup analyses conducted based on implant number (≤ 4 vs. > 4), impression type (intraoral scanners vs. photogrammetry), and study design (in vitro vs. in vivo). Publication bias was assessed using funnel plots and Egger's regression test. Risk of bias was evaluated using QUIN for in vitro studies, RoB 2 for randomized trials, and ROBINS-I for non-randomized studies.

A total of 37 studies were included, comprising 30 in vitro and 7 in vivo investigations, with the latter including 3 randomized clinical trials, 3 prospective studies, and 1 retrospective study. The studies assessed impression accuracy using 3D global deviation and/or coordinate measuring machine (CMM) analysis. Meta-analysis of 25 studies revealed no significant overall difference in accuracy between digital and conventional impressions (standardized mean difference [SMD]: -0.03; 95% CI: -0.20 to 0.14; p = 0.74), although substantial heterogeneity was present (I² = 68%). Subgroup analysis showed no significant difference for cases with ≤ 4 implants, while conventional methods were slightly favored in cases with > 4 implants (SMD: 0.22; 95% CI: 0.05 to 0.39; p = 0.01). Photogrammetry produced slightly greater accuracy than conventional impressions (SMD = 0.15; 95% CI 0.02 to 0.28), whereas intraoral scanners did not differ from conventional techniques. Funnel-plot asymmetry and Egger testing suggested publication bias. Certainty of evidence was judged moderate owing to methodological heterogeneity and imprecision. Descriptive findings indicated that 12 studies reported comparable accuracy between techniques, 11 favored conventional impressions, and 13 favored digital methods. One study noted implant number as a factor, with conventional methods more accurate for three implants and digital techniques superior for four or more. These results highlight both methodological variability and a lack of consensus in the current evidence.

Digital impressions achieve accuracy comparable to conventional impressions in most clinical situations. Accuracy may decline when scanning arches with more than 4 implants, although photogrammetry appears to mitigate this effect. Well-designed in vivo studies that use standardized scanning and evaluation protocols are needed to confirm these findings and to define clinical thresholds for adopting specific digital workflows.