Marginal gap measurement of ceramic single crowns before cementation: A systematic review

Different instruments have been used to measure the marginal gaps of crowns in vitro. However, a comprehensive systematic review is lacking.

The purpose of this systematic review was to evaluate the existing literature on the instruments used for the in vitro marginal gap measurement of ceramic single crowns before cementation and to determine whether the crown material and method of fabrication influenced the marginal gap.

The search was conducted in 2024 across the EBSCO Host, Scopus, PubMed, and Web of Science databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and predefined eligibility criteria. Eligible articles were screened to evaluate 6 instruments for measuring crown marginal gaps: direct view microscopy, scanning electron microscopy, impression replica, cross-sectioning, microcomputed tomography, and 3-dimensional (3D) superimposition. The normality of the data was assessed by using the Kolmogorov-Smirnov test, and the differences in mean marginal gap were statistically evaluated using the Welch ANOVA (α=.05).

Ninety-two articles were included, with 77 documenting single measurement instruments and 15 using a combination of 2 or more measurement instruments. Direct view microscopy was the most used instrument and appeared in 31 (40%) of the studies. No significant differences in mean marginal gap (F=2.09, P=.077) were found across the 6 measurement instruments. Across all studies, excluding those using 3D superimposition, the mean ±standard deviation number of marginal gap measurements per crown was 34.3 ±50.6. Among the 77 studies using a single measurement instrument, 64 used computer-aided design and computer-aided manufacturing (CAD-CAM) technology to fabricate the crowns. CAD-CAM crowns had a mean ±standard deviation marginal gap of 78.9 ±28.6 µm (n=64) compared with 71.6 ±29.5 µm (n=13) for crowns manufactured using conventional methods. Zirconia and lithium disilicate were the most researched materials. Zirconia crowns recorded a mean ±standard deviation marginal gap of 69.4 ±34.2 µm for 972 crowns, which was significantly different (P=.045) from lithium disilicate with a mean ±standard deviation marginal gap of 92.2 ±42.5 µm for 602 crowns.

Direct view microscopy was the most used marginal gap measurement instrument for ceramic single crowns before cementation, and CAD-CAM was the most used crown fabrication method. No significant differences in mean marginal gap were found among the 6 marginal gap measurement instruments.