The aims of this study were to investigate the applicability of composite resin veneered polyetheretherketone (PEEK) crowns to dental restorations, and to evaluate fracture loads and failure modes of PEEK-based crowns with two framework designs.

 A stainless-steel die was prepared for a maxillary molar crown restoration. Resin abutments were duplicated. Composite resin veneered PEEK crowns with two different PEEK framework designs (uniform-thickness (STD); supported-design (EXP)), and Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) composite resin crowns (CRC) were fabricated. The restorations were cemented to abutments and loaded vertically until fracture. Fracture loads were recorded for each specimen. Failure modes were observed and statistically analyzed.

 The fracture loads of the STD, EXP, and CRC specimens were 1610.9 N, 1680.8 N and 1698.0 N, respectively. There were no significant differences among the groups. For STD and EXP, almost all specimens showed restorable failure; however, CRC specimens showed a significantly higher ratio of non-restorable failure.

 Composite resin veneered PEEK crowns can be applied to dental restorations in the molar regions and showed high fracture load, regardless of framework design. They also showed a failure mode with less influence on the abutment tooth at a high rate compared with CAD/CAM crowns.

 The aim of this study was to evaluate the detectability and the reproducibility of the edge including small step.

 Specimen was Step Master, which has known dimension, and was scanned with 2 laboratory (D900 and map400) and 2 intraoral scanners (Trios3 and CS3600), each 10 times. The reference model, which has same size and steps as the specimen, was designed by CAD software. The edge of each block was designed with a right angle. Scanned model and reference model were superimposed. An analytical region on the scanned model including step of 300μm was determined. The mismatched of scanned edge region with respect to the reference model was selected, and a best-fit cylinder to data points within the selected area was designed. The radius of cylinder was calculated to evaluate the reproducibility of the edge. The number of triangles within the square area (1.0×1.0 cm²) was counted and the size of those was observed.

 All 4 scanners could detect the edge. There were significant differences of the corner radius among the 4 scanners. Our evaluation method using the corner R value has a possibility that can assess the finish line edge 3-dimensionally and quantitatively.