Effect of Luting Cement on Marginal and Internal Adaptation of Novel Ceramic-Reinforced Polymer Crowns: A Micro-CT Study

A novel alumina-filled ceramic-reinforced polymer (CRP) crown (Hassawat-01; HS) was developed. This study evaluated the effect of luting cement on the marginal and internal adaptation of HS and compared its performance with a commercial DLP-printed CRP (VarseoSmile Crown Plus®; VS) and a milled resin nanoceramic (Cerasmart® 270; CE). Ninety-nine crowns (n = 33/material) were fabricated with a 50 µm cement space and luted using Maxcem Elite®, RelyX Unicem®, or Ketac Cem® (n = 11/subgroup). Adaptation was assessed without and with cementation using micro-computed tomography at 160 measurement points per crown. Without cementation, HS demonstrated the most favorable internal adaptation, whereas VS showed the best marginal adaptation. Following cementation, gap dimensions increased in all groups. Despite its superior non-cementation fit, HS exhibited the greatest increase in marginal and internal discrepancies, suggesting increased hydraulic resistance during seating. Among the evaluated cement–crown combinations, VS luted with RelyX Unicem® showed the most favorable post-cementation adaptation. Post-cementation analysis was limited to HS and VS because the radiopacity of CE prevented reliable cement interface segmentation. These findings indicate that adaptation is influenced by both crown geometry and cement properties, and that highly adapted intaglio surfaces may require careful cement selection to optimize clinical fit.