Marginal gap of ceramic crowns fabricated by CAD-CAM and conventional techniques: A systematic review and...

The marginal gap in ceramic crowns is a critical parameter for the biological integrity and long-term success of restorations. Although computer-aided design and computer-aided manufacturing (CAD-CAM) systems have been reported to provide a more predictable manufacturing process by reducing operator-dependent variability, the evidence comparing the marginal gap of CAD-CAM and conventional methods remains inconsistent.

The purpose of this systematic review and meta-analysis was to quantitatively compare the marginal gap of ceramic crowns fabricated using CAD-CAM versus conventional laboratory techniques and to estimate the mean difference between the 2 approaches.

A comprehensive search was conducted in the PubMed, Scopus, Web of Science, Embase, the Cochrane Library, and Google Scholar databases without restrictions on year or language. In vitro studies reporting comparative marginal gap values (mean, standard deviation, and sample size) for crowns fabricated with CAD-CAM and conventional methods were included. The pooled effect size was calculated using a random-effects model (DerSimonian-Laird). Heterogeneity was assessed using the Q statistic, I² statistic, and between-study variance (τ²). Publication bias was evaluated using funnel plots and the Egger regression test. Sensitivity analyses were performed using a leave-one-out approach.

A total of 16 studies were included in the meta-analysis. The pooled mean difference was not statistically significant (mean difference [MD]=-2.3 µm; 95% confidence interval [CI], -10.6 to +5.9 µm; P=.582). Heterogeneity was substantial (I²=95.2%), largely attributable to the study using microcomputed tomography (µCT), which exhibited lower variance and different distributional characteristics compared with other measurement techniques. Leave-one-out analyses indicated that no single study materially altered the direction or statistical significance of the overall estimate. Importantly, in both groups, all marginal gap values remained below clinically acceptable thresholds (<120 µm).

Ceramic crowns fabricated using CAD-CAM and conventional techniques demonstrate comparable marginal gaps. While CAD-CAM systems may reduce cumulative errors and enable a more standardized workflow under certain clinical conditions, meticulously performed conventional techniques by experienced dental laboratory technicians can achieve similarly successful outcomes. Because the marginal gaps were within clinically acceptable limits for both methods, technique selection should not be based solely on marginal gap; rather, broader clinical parameters-such as preparation geometry, material selection, clinical workflow, and operator experience-should be decisive in the decision-making process.