Dimensional accuracy and flexural strength of 3D-printed photopolymer resins for point-of-care surgical guides after steam and plasma sterilization: an in-vitro comparative study

Abstract Background Three-dimensional (3D) printing enables the fabrication of patient-specific guides (PSGs) for oral and craniomaxillofacial procedures. Before clinical use, guides must be sterilized, which may compromise dimensional accuracy and mechanical performance. The effect of the extended sterilization cycle required for prion inactivation, which holds 134 °C for at least 18 min, has not been evaluated on contemporary guide resins. This study evaluated the impact of steam and plasma sterilization on the dimensional accuracy and flexural strength of four 3D-printed photopolymer resins, assessed using standardized specimens and clinically relevant surgical guides. Materials and methods Four biocompatible resins (P pro Surgical Guide Clear (PR), ProArt Print Splint (PI), BioMed Clear Resin (BC), BioMed Amber Resin(BA)) were investigated using stereolithography (SLA) and digital light processing (DLP) 3D printing technologies. ISO-standard specimens ( n = 240) were fabricated for dimensional accuracy and flexural strength testing. Clinically relevant surgical guides ( n = 72) representing cranial resection and oral implantology procedures, were printed for dimensional accuracy assessment. Specimens were randomly allocated to three groups: baseline (non-sterilized), steam sterilization (134 °C, 18 min), and plasma sterilization (55 °C, 19 min). Dimensional accuracy was evaluated by root mean square (RMS) analysis, and flexural strength was determined by three-point bending. Two-way ANOVAs were conducted, followed by Bonferroni post-hoc test (α = 0.05). Results Dimensional accuracy varied significantly by specimen type and was overall highest (lowest RMS) for the ISO specimens used in flexural testing (61 ± 24 μm), followed by cranial guides (119 ± 29 μm) and oral implantology (dental) guides (147 ± 45 μm). Materials PI and PR demonstrated higher dimensional accuracy than BC and BA across all geometries ( p < 0.001). Sterilization method significantly affected dimensional accuracy overall ( p < 0.001), with the extent of change varying by specimen geometry. Steam sterilization increased the flexural strength of the ISO specimens (41 ± 16 MPa) compared to baseline (33 ± 19 MPa), while plasma sterilization decreased it (29 ± 16 MPa) ( p < 0.001). Critically, all steam-sterilized PSGs from BC and BA materials developed visible cracks, while plasma-sterilized guides remained intact. Conclusions Material selection and sterilization method significantly affected the dimensional accuracy and flexural strength of 3D-printed PSGs, and the flexural strength of standardized specimens fabricated from the same resins. Steam sterilization caused crack formation in guides fabricated from BC and BA despite increasing flexural strength, rendering them clinically unusable. Plasma sterilization avoided this structural failure but reduced flexural strength and remains unvalidated for hydrogen peroxide clearance in these resins, so it cannot be recommended as a default substitute without further validation. Material and sterilization methods should instead be selected and validated as a pair, matched to the sterilization cycle applied at the point-of-care and to the mechanical and accuracy demands of the intended procedure.