Marginal and internal fit of implant-supported full-arch frameworks fabricated using different material–manufacturing workflows: a micro-CT study

The purpose of this in vitro study was to compare the marginal and internal fit of implant-supported full-arch frameworks composed of cobalt–chromium (Co–Cr), zirconia, biocompatible high-performance polymer (BioHPP), and polyetheretherketone (PEEK) using different material–manufacturing workflows. A master model and six abutment-level analogs were used to replicate an edentulous maxilla. Thirty-five 12-unit frameworks were manufactured. Seven frameworks were allocated to each of the five workflow groups: Lost Wax (LW), Direct Metal Laser Sintering (DMLS), Zirconia (ZIR), PEEK, and BioHPP. A total of 210 silicone replicas were produced, with 35 replicas obtained from each implant position ( n = 6). The silicone replicas were scanned and sectioned using micro–computed tomography, and a total of 3,360 reference points (16 points per replica) were evaluated. Linear mixed-effects model analysis revealed significant differences among the material–manufacturing workflow groups for both marginal ( p = 0.034) and internal gap values ( p = 0.019), whereas implant position had no significant effect on either outcome ( p > 0.05). The PEEK group exhibited significantly higher marginal gap values than the DMLS Co–Cr and BioHPP groups (adjusted p = 0.032 and p = 0.029, respectively). For internal fit, BioHPP showed the lowest mean gap value (181.1 ± 34.2 μm) and demonstrated significantly lower values than lost-wax Co–Cr and DMLS Co–Cr (adjusted p = 0.010 and p = 0.030, respectively). Within the limitations of this in vitro study, significant differences in marginal and internal fit were observed among the evaluated material–manufacturing workflow groups. BioHPP and DMLS Co–Cr demonstrated lower marginal gap values than PEEK, whereas BioHPP exhibited the lowest mean internal gap among the evaluated groups.