Effect of layer thickness, inner structure, and implant angulation on the accuracy of 3D printed models with implant analogs

Objective: This study evaluated the effect of layer thickness, model inner structure, and implant angulation on the accuracy of 3D printed models with repositional analogs. Materials and methods : 126 models designed to receive all-on-4 implant retained fixed dental prosthesis were 3D printed. Models were divided into 2 groups (n=63) according to posterior implant angulation (Group 1; 30˚ and group 2;45˚). The models were then divided into three sub-groups (n=21) according to the printing layer thickness (Group a; 50 µm, group b; 100 µm, and group c; 150 µm). Each subgroup was later subdivided into 3 divisions (n=7) according to the model inner structure (Group I; solid, group II; hollow, and group III; honeycomb). Trueness was analyzed using Geomagic controlX analysis software by comparing the model scans to the reference model STL file. Results: Both inner structure and layer thickness had a significant effect on the final accuracy (p<0.001). Distal implant angulation had no effect on the final accuracy of the printed model (p=0.968). Regarding layer thickness, tukeys post-hoc test revealed that both 100 µm (24.9 ± 2.4) and 150 µm (24.5 ± 1.1) layer thickness showed higher accuracy than the 50 µm (27.9 ± 2.4) layer thickness. As for model form, tukeys post hoc test revealed that the solid (24.9 ± 1.4) and honey-comb (25 ± 1.5) models were more accurate than the hollow models (27.5±3.3). Conclusion: Implant angulation had no effect on the final accuracy of the model. Both 50 µm print layer thickness and hollow model inner structure showed the least accuracy. Clinical relevance: Printing layer thickness of 100 to 150 µm with a solid or honeycomb model inner form will provide the best 3D positional accuracy for implant analogs