Exploring hot isostatic pressing as a thermo-mechanical treatment for additive and milled CAD-CAM screw-retained frameworks: trueness, marginal and internal gap assessments

Additive framework construction for patients with edentulous arches still lacks consolidated guidelines regarding manufacturing and post-processing technologies. To evaluate the impact of post-treatment hot isostatic pressing (HIP) in dental frameworks, an edentulous maxillary replica (EMR) with the all-on-four concept was fabricated, and Ti-6Al-4V dental frameworks were manufactured by milling, Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM) technologies. The EMR and frameworks were scanned by the triple-scan technique, and the assessments of vertical and internal gaps, horizontal discrepancies, and trueness were evaluated before and after a HIP cycle (920 °C, 100 MPa for 2 h). Laser scanning confocal microscopy analyzed the frameworks surface. Results demonstrate EBM technology displayed a lower vertical gap at baseline and after HIP, and the HIP was beneficial for both DMLS and milling groups, reducing their vertical gap. Adequate lateral and internal fit were found for all groups. The HIP increases both lateral and internal gap for all groups, which is beneficial considering prosthesis assemble. EBM and DMLS presented positive results regarding horizontal discrepancies. Trueness analysis proved that DMLS and EBM technologies can be considered as viable options for dental framework constructions, as no differences were found between the groups on the abutment-framework interface, and that HIP can alter both areas with more complex geometry and areas with a uniform geometry, which can provide benefits for vertical, internal and horizontal measurements. Altogether, the assessment of distortions with 3D scanning technology can help predict the clinical prostheses prognosis, since internal spaces between framework and abutment can be measured.