Influence of printing parameters on the fabrication and fit accuracy of additively manufactured resin-based definitive three-unit fixed partial dentures.

Objective
To assess how build orientation and layer thickness affect the fabrication and fit accuracy (trueness and precision) of additively manufactured resin-based definitive fixed partial dentures (FPDs), comparing with subtractively manufactured FPDs.
Methods
Three-unit posterior FPDs were fabricated additively in a resin for definitive use (VarseoSmile Triniq) with varying build orientations (0-, 30-, 45-, 90-degree) and layer thicknesses (50, 100 µm) (AM0-50, AM0-100, AM30-50, AM30-100, AM45-50, AM45-100, AM90-50, and AM90-100) or subtractively in high-impact composite (breCAM.HIPC, SM-CR, control) (n = 6). Surface deviations (external, internal, marginal), fit (average gap), and their precision, which was the average of deviations from the mean deviation or gap values, were analyzed. AM FPDs were analyzed using a generalized linear model, while one-way analysis of variance with Dunnett's test was used for comparisons with SM-CR FPDs (α = 0.05).
Results
Build orientation and layer thickness interaction affected the deviations and average gaps of AM FPDs, and build orientation affected marginal surface precision (P ≤ 0.044). AM30-50 and AM90-50 FPDs generally had lower deviations and average gaps, while 90-degree orientation resulted in lower marginal precision (P ≤ 0.020). AM30-50 and SM-CR FPDs had similar external and marginal deviations (P ≤ 0.370). AM90-50 FPDs had lower external deviations than SM-CR FPDs (P = 0.011). AM FPDs had higher intaglio deviations and average gaps than SM-CR FPDs (P < 0.001).
Conclusions
FPDs additively manufactured with 30- and 90-degree build orientation and 50-micron layer thickness had accuracy similar to SM-CR FPDs. However, SM-CR FPDs had better fit than AM FPDs.