The efficacy of the inherent strain method in laser powder bed fusion to distortion compensate in removable partial dentures

Abstract

Laser powder bed fusion (LPBF) is increasingly adopted in dentistry for the production of removable partial dentures (RPDs) and implant-supported RPDs (ISRPDs), offering advantages over conventional casting through digital workflow integration and reduced operator variability. However, thermally induced residual stresses during LPBF frequently cause distortion, compromising the geometric accuracy and clinical fit of these prostheses. This study investigates the efficacy of distortion compensation based on the inherent strain method implemented within a finite element framework. An orthotropic calibration procedure was developed using cantilever specimens manufactured parallel to the principal build directions. Distortion measurements were obtained using coordinate measurement machine (CMM) analysis following stress relief sectioning. Validation specimens were subsequently fabricated at 30° and 45° relative to the principal build direction to assess the predictive capability of the calibrated inherent strain model. The calibrated strain values were implemented in Simufact Additive to pre-distort digital mandibular and maxillary RPD geometries prior to fabrication. Geometrical deviations were quantified using intraoral scanning and comparison of predefined datum points between the nominal CAD models and as-built components. Distortion compensation resulted in a maximum local improvement of 410 µm and reduced mean maximum deviation by 23% and 27% for mandibular and maxillary frameworks, respectively, compared to uncompensated controls. The compensated dentures showed improved dimensional fidelity, with most deviations falling within clinically acceptable thresholds reported in recent literature, although localized deviations remained. The method demonstrated robustness across non-orthogonal build orientations and mesh refinements. These findings indicate that inherent strain-based distortion compensation can enhance the geometric accuracy of LPBF-fabricated dental prostheses and support improved integration of simulation-driven workflows in digital prosthodontics.