Measuring the Marginal Gap of Pre-Cemented All-Metal Single Crowns: A Systematic Review of In Vitro Studies

Background: Different methods have been used to fabricate and measure marginal gap in all-metal crowns, yet a systematic review on this topic has not been conducted. Objective: To review the existing literature regarding the measurement methods employed for the in vitro marginal gap measurement of pre-cemented all-metal single crowns and examine the influence of crown fabrication method on the marginal gap. 

Materials and Methods: A systematic search was performed from December 2024 backwards across EBSCO Host, Scopus, PubMed, and Web of Science databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and predefined eligibility criteria. The quality of included articles was evaluated using the Joanna Briggs Critical Appraisal Checklist. 

Results: Ten studies, involving 180 crowns, assessed marginal gaps using computerised superimposition (102 µm), scanning electron microscopy (89 µm), profilometry (100 µm), photogrammetry (59 µm), impression replica techniques (124 µm), and direct view microscopy (35 µm). Marginal gaps varied across crowns constructed with cobalt–chromium (97 µm), titanium (56 µm), noble metals (127 µm), and base metal alloys (35 µm). No significant differences (t = 1.06, p = 0.315) were observed between CAD/CAM (103.21 ± 58.56 µm) and lost wax casting method (71.59 ± 43.94 µm) of crown fabrication when analysed using an independent t-test. 

Conclusions: Cobalt–chromium was the most used material for AMCs, while titanium alloys produced the lowest mean marginal gap per crown. No significant differences in reported marginal gaps were observed between crowns fabricated using lost wax casting and CAD/CAM techniques. However, the limited number of studies, variation in measurement methods, and inconsistency in methodological rigour restricted the generalisability of the findings.