Accuracy of additive and subtractive hybrid fabrication of complete-arch implant titanium frameworks

Objective To evaluate the difference in accuracy of edentulous titanium implant frameworks fabricated using subtractive and additive-subtractive hybrid fabrication techniques. Methods Implant frameworks for a maxillary edentulous jaw model with 6 implants were designed using design software(EXOCAD) and exported as STL files. Five titanium implant frameworks were fabricated using subtractive manufacturing(SM) and additive-subtractive hybrid manufacturing(AM-SM) techniques, respectively. The 3D coordinates of the center points of the upper and lower planes of each implant abutment-prosthesis interface were obtained by using a coordinate measuring machine, and were “best-fit-aligned” to the original STL files in a specific software to obtain the linear deviation of the center points of the upper and lower planes of each interface in the x, y, and z axes, and the 3D deviation of each implant abutment-prosthesis interface. The centroid coordinates were imported into a reverse-measurement software(Geomagic Control X) and the angular deviation of each interface was calculated by creating “line features”. Statistical tests were performed using Kruskal-Wallis, ManneWhitney U, and one-way ANOVA(α=0.05). Results Between the differences in the implant abutment-prosthesis interfaces of the two fabrication methods, there was no statistical difference in the linear deviation on the x, y, and z axes of each interface and the 3D deviation and angular deviation of the interface(P>0.05), and the deviation values were within the clinically acceptable range. There were statistically significant differences in the 3D deviation between the different implant sites of the edentulous implant frameworks in both techniques. Conclusion Fabrication techniques do not affect the accuracy of the implant abutment-prosthesis interface. The accuracy of edentulous fixed implant frameworks fabricated by additive-subtractive hybrid fabrication techniques is within the clinically acceptable range. The implant site has a certain influence on the accuracy of the implant framework.