Passive fit of milled and additively manufactured complete arch implant-supported titanium frameworks: a micro-CT analysis

Background: To evaluate the passive fit of milled and additively manufactured titanium complete arch implant-supported frameworks (CAISFs) by using microcomputed tomography (µCT). Methods: A maxillary model resembling all-on-4 concept was used, multiunit abutments and scan bodies were attached, and the model was digitized. Ten frameworks were produced from CAD files and allocated to 2 groups (n=5) according to the manufacturing method: milled titanium (M) and additively manufactured titanium (AM). The passive fit of CAISFs was evaluated by using the modified 1-screw test. All screws were attached and then removed, except for the terminal abutment tightened to 15 Ncm. The Primary outcome to access passive fit involved measuring marginal discrepancies for the 3 unscrewed implants at 4 points using µCT. Mann-Whitney U test assessed manufacturing methods. Kruskal-Wallis test assessed effect of implant locations and different measuring surfaces on marginal discrepancy. Aligned rank transform (ART) ANOVA was used to evaluate the effect of the interactions among all factors (α=.05). Results: Regarding the passive fit, significant difference in marginal discrepancy value was found between the 2 manufacturing methods (P<.001). AM group had lower marginal discrepancy value (44 ±4 μm) than M group (49 ±5 μm). No significant differences in marginal discrepancy value were found among the 3 implant locations (P=.822). Statistically significant differences were found among the 4 measurement surfaces (mesial, buccal, lingual, distal) (P<.001). ART ANOVA showed that the interaction among manufacturing method, implant location, and measurement surface was not statistically significant (P=.992). Conclusion: Additively manufactured titanium CAISFs demonstrated better passive fit than milled ones. However, both additive manufacturing and milling techniques produced titanium CAISFs with clinically acceptable marginal discrepancy. The proximity of the implant location to the screwed implant did not affect the marginal discrepancy. Clinical implications: Additively manufactured and milled titanium frameworks demonstrated superior marginal fit, suggesting their potential applicability and advantage in clinical practice.