The effect of build angle and intraarch connector design on the accuracy and fit of additively manufactured complete-arch implant-supported interim fixed prostheses

OBJECTIVES: To evaluate the effect of intraarch connector design and build angle on the fabrication trueness and precision, and overall accuracy, of additively manufactured (AM) compared to subtractively manufactured (SM) frameworks in high-impact polymer composite (HIPC) for complete-arch implant-supported prostheses on four implants. METHODS: A typodont model with four implants and their multiunit abutments were digitized and an implant-supported complete-arch framework was designed. Three design files (no bar, horizontal bar, Y-shaped bar) were used to fabricate AM specimens using a glass-filler-reinforced composite resin in three different build angles (0°, 45°, 90°) (n = 10). Ten SM frameworks fabricated from HIPC served as the control group. All frameworks were digitized and superimposed. Trueness and precision were evaluated in separate regions, as well as linear abutment and interimplant distance deviations. Marginal gaps were evaluated after seating the frameworks with one screw inserted in left posterior abutment. Data were statistically analyzed (α = 0.05) RESULTS: Both build angle and intraarch connector design significantly affected trueness, precision, linear deviations, and marginal gaps. Compared to the control group, test groups mostly showed similar or lower accuracy. No clear pattern among other test groups was observed. Marginal gaps differed significantly among groups (p < 0.05), ranging from 50.2 µm at the right posterior abutment in the 0°-no-bar group to 573.7 µm at the left anterior abutment in the 90°-horizontal-bar group. 0° no-bar mostly showed the lowest surface deviation, lowest linear deviation, and least marginal gaps (p < 0.05). CONCLUSIONS: Within the limitations of this single-system in vitro study, AM complete-arch implant-supported interim fixed prostheses in a 0° no-bar configuration demonstrated accuracy comparable to SM HIPC. The marginal gaps found in some groups were beyond clinical acceptability. Printing such prostheses in 45° and 90° configurations using the tested printer, resin, and post-processing combination cannot be recommended. CLINICAL SIGNIFICANCE: The differences in marginal gaps found between the groups showed magnitudes beyond clinical acceptability and therefore additive manufacturing of complete-arch implant-supported interim fixed prostheses using build angles other than 0°and/or incorporating intraarch connectors should be approached with caution.