Comparison of marginal adaptation and fracture strength of PEEK endocrown restorations fabricated using additive and subtractive methods

Abstract

Aim: The aim of this in vitro study was to compare the marginal fit and fracture strength of endocrown restorations applied to maxillary canines, using different manufacturing methods.

Methodology: An extracted upper canine tooth was prepared for endocrown placement. Three methods were used to create the endocrowns: Fused Deposition Modeling (FDM) 3D printing with Essentium Polyetheretherketone (PEEK) filament, CAD/CAM milling with Juvara PEEK disk, and SLS 3D printing with Cr-Co metal (N=10). Additionally, 30 identical canine tooth replicas were produced using an Asiga 3D printer with a model resin, and the crown restorations were cemented with a resin luting cement. Fracture strengths were tested, and marginal fits were evaluated using Geomagic Control X software. Statistical analysis was performed, and Weibull analysis was used to assess fracture strength values.

Results: The laser-sintered endocrowns exhibited higher fracture strength (1351 N) compared to PEEK FDM (735.341 N) and milled PEEK (826.733 N) endocrowns. The highest Weibull modulus was found for milled PEEK (3.978), while the lowest was for the Cr-Co laser-sintered material (2.912). A significant difference in marginal fit was observed on the palatal surface of the PEEK FDM group compared to the other two groups (p=0.048). However, no significant differences were found on the mesial, distal, or buccal surfaces.

Conclusion: The findings indicate that PEEK endocrowns produced by FDM and milling offer clinically acceptable fracture strength and marginal fit, with PEEK being closer to the dentin elastic modulus. The significantly higher Weibull modulus of PEEK endocrowns produced by the FDM Printer and milling enables us to make more accurate intraoral fracture predictions.