Marginal and internal fit of CAD/CAM restorations with CAD-defined cement space: a meta-analysis of micro-CT studies

In fixed restorations produced with a fully digital workflow, there is limited meta-analytic evidence examining the relationship between predefined cement gap and marginal/ internal fit.

The purpose of this meta-analysis is to examine the pooled marginal and internal fit of CAD/CAM restorations in studies in which cement space was predefined numerically during the CAD design stage and fit was assessed using micro-computed tomography (Micro-CT).

The search was conducted between 2013 and 2024 across the PubMed, Scopus, Science Direct and Google Scholar databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and predefined eligibility criteria. Based on CAD/CAM fixed restorations and Micro-CT analysis, 2 groups were categorized in terms of marginal and internal fit, and 4 subgroups in terms of cementation and scanner. A meta-analysis was conducted across multiple studies using a random-effects model (p < 0.05). Expected heterogeneity was assessed among the studies and subgroup analysis was also performed.

41 articles were included for marginal, and 39 articles for internal fit. All included studies were assessed as having a low risk of bias. The mean marginal fit was 105.66 μm (95% CI: 91.55-119.78), and the overall mean internal fit was 138.57 μm (95% CI: 122.56-154.58). High heterogeneity was seen in both main groups. In the cemented subgroup, the mean marginal fit was 137.67 μm, and the mean internal fit was 181.87 μm. In the non-cemented subgroup, the mean marginal fit was 103.19 μm, and the mean internal fit was 131.67 μm. In the EOS subgroup, the marginal fit was 102.79 μm, and the internal fit was 132.04 μm. In IOS, marginal and internal fit were 109.83 μm and 148.02 μm, respectively.

Within the limitations of this meta-analysis, pooled marginal and internal fit values varied across studies despite predefined cement space during the design stage. Subgroup analyses suggested that cementation status and scanner type may influence the reported fit values. However, these findings should be interpreted cautiously due to substantial heterogeneity and variability in study conditions.

In CAD/CAM restorations with predefined cement space, clinicians should be aware that reported marginal and internal fit values may vary depending on material, workflow, and measurement conditions. Therefore, clinical interpretation should be made cautiously, particularly for internal fit, where universally accepted thresholds remain unclear.