Objectives: To investigate the effect of layer height on the accuracy of orthodontic models utilising fused filament fabrication, particularly with regard to optimising in-office aligner manufacture. The suitability of fused filament fabrication was assessed by comparing the results to a high precision digital light processing control group.
Materials and methods: Based on a digital sectioned maxillary model, 18 physical models were printed using fused filament fabrication technology at different layer heights (50.0 μm, 80.9 μm, 100.0 μm, 150.0 μm, 160.8 μm, 200.0 μm, 250.0 μm, 300.0 μm and 332.6 μm) using two different materials (polylactide PLA NX2 and lignin-based polymer Green-TEC PRO [Extrudr, Lauterach, Austria]). Two DLP models with a layer height of 20.0 μm were produced, representing the control group. Subsequently, all physical models were digitally scanned and compared via 3D superimposition using GOM Inspect software (GOM, Braunschweig, Germany).
Results: The Dahlberg analysis and intraobserver intraclass correlation proved the accuracy of the 3D superimposition measurement to be excellent and repeatable. Models printed using fused filament fabrication technology from lignin-based polymer within the range of 100.0 to 332.6 μm decreased in precision as layer height increased. Furthermore, the analysis recorded declining precision of fused filament fabrication models below 100.0 μm. Models printed using lignin-based polymer were superior in precision compared to those made from polylactide.
Conclusions: The accuracy and precision of fused filament fabrication models can be regulated by altering layer height; however, other parameters such as optimised printing material and print settings are necessary for consistent high quality. As such, fused filament fabrication printing is an accurate, cost-effective and sustainable technology to create aligner models in orthodontic practice.
Keywords: 3D printing, 3D superimposition, digital light processing, fused filament fabrication, orthodontic models
