Manufacturing trueness, internal fit, and planned-to-intraoral spatial concordance of monolithic zirconia crowns fabricated with two commercial ti-base systems: a clinical cross-sectional study

Abstract

The aim of this clinical cross-sectional study was to evaluate manufacturing trueness, internal fit, planned-to-intraoral spatial concordance, and proximal contact discrepancy in implant-supported monolithic zirconia crowns fabricated within two commercial ti-base restorative systems. Thirty-one patients received implant-supported single-unit monolithic zirconia crowns fabricated within either a Flat or Tab commercial ti-base restorative system using a fully digital workflow. The systems differed in manufacturer and associated components or parameters, including proprietary scan bodies and CAD libraries, abutment height, and manufacturer-recommended cement gap; accordingly, this was a system-level comparison rather than an isolated test of ti-base interface geometry. For each restoration, four STL datasets represented the initial intraoral situation, the CAD crown design, the manufactured crown, and the intraoral condition after fitting. A modified triple-scan protocol and metrology-grade software were used. Manufacturing trueness and planned-to-intraoral spatial concordance were quantified using root mean square deviation values. Because the planned and observed datasets were propagated within the same digital workflow and no independent external reference was used, the spatial outcome was interpreted as workflow concordance rather than absolute clinical trueness. Internal fit was assessed by triple-scan gap analysis, and proximal contact discrepancies were digitally measured. Statistical analyses were performed using Student’s t test and repeated-measures ANOVA with significance set at p  < 0.05. No statistically detectable between-system differences were found for manufacturing trueness, internal fit, planned-to-intraoral spatial concordance, or proximal contact discrepancies ( p  > 0.05). Spatial RMS values were consistently higher than manufacturing RMS values in both systems ( p  < 0.001). Internal fit values for both systems were within commonly cited clinical thresholds. Both commercial ti-base systems showed mean manufacturing RMS values below 60 μm and internal fit within commonly cited clinical limits. Planned-to-intraoral spatial RMS values were consistently higher than manufacturing RMS values in both systems, indicating that high manufacturing trueness alone does not imply high planned-to-intraoral spatial concordance. Manufacturing trueness alone may be insufficient to characterize planned-to-observed intraoral concordance; evaluation of the final intraoral position provides complementary workflow information.