The Passivity of Implant-Supported Monolithic Zirconia two-Unit Fixed Partial Denture Screwed to Multi-Unit Abutments With and Without a Titanium Base

Objectives:
The passive fit of an implant-supported framework is described as maximal coherency between the prosthesis-implant interface, ensuing in no strains after screw tightening.
Sheffield test is an efficient test for clinical evaluation of passive fit, when one screw on the distal abutment is completely tightened without creating a gap between the other abutments and cylinders.
The purpose of this study was to assess and compare the passivity fit of implant-supported monolithic zirconia two-unit fixed partial denture screwed to multi-unit abutment with and without a titanium-base using the Sheffield test (the one-screw test) technique.
Null hypothesis: Using a titanium base (Ti-base) would not affect the degree of fit at the framework-implant interface.
Methods:
Fifty monolithic zirconia FPDs (2-unit crowns) were screwed to straight MUAs torqued to laboratory analogs (15 Ncm) and assigned to two groups. Each group has 25 samples. In group A, the zirconia crowns were screwed directly to the MUAs; in group B, the zirconia crowns were cemented to the Ti base and screwed to the MUAs.
Straight MUAs torqued to laboratory analogs with a digital torque ratchet (30 Ncm) (CEDAR Model DIW 15).
For vertical marginal discrepancy (VMD) evaluation, each framework was fixed on the typodont model by 1 screw at a torque of 15 Ncm. In addition, images were captured of the non-screw-retained side. A total of 6 measurement points (1 mesiobuccal, 1 mid-buccal, 1 distobuccal, 1 mesiolingual, 1 mid-lingual, and 1 distolingual) were evaluated.
The points were examined using a scanning electron microscope (SEM). In total, 600 VMD values were recorded.
Results: The results of 2-way ANOVA (Table 1) of the Sheffield test determined that the mean VMD values were not significantly influenced by the evaluation site (P=.395). Moreover, the interaction of variables (evaluation site with and without t base) was not statistically significantly different.
Conclusions: Both groups (with and without Ti-base) frameworks had clinically acceptable values (<150m).
Using a screwed zirconia framework with Ti-base did not significantly affected the passive fit.