EAO‐204/PO‐BR‐023 | Effect of inaccurate implant positions on passive fit of screw‐retained implant‐supported frameworks

Daniel Kules*; Julius Dirse; Vygandas Rutkunas

Institute of Odontology, Faculty of Medicine, Vilnius University, Vilnius, Lithuania

Background: The term “passive fit” refers to the ideal fit of the prosthetic framework to the implant when the opposing surfaces of the implants and the framework intaglio are in maximal spatial congruency without generation of any stress. Little is known how implant-supported screw-retained frameworks with different combinations of engaging (E) and non-engaging (NE) titanium bases can tolerate inaccurate implant positions.

Aim/Hypothesis: The purpose of this study was to simulate horizontal and vertical implant positioning errors and to evaluate the passive fit of two-implant-supported screw-retained zirconia frameworks with three different combinations of the abutments: E-E, E-NE, and NE-NE.

Material and Methods: The fit of E-E (n = 10), E-NE (n = 10) and NE-NE (n = 10) two-implant-supported zirconia frameworks were evaluated on control and study models simulating 50, 100, 150 μm vertical (V) and 35, 70, 100 μm horizontal (H) implant positioning errors. Vertical deviations (the implant-abutment gap measured vertically) between implant platform and reference line on titanium base were measured using a stereo microscope when only one abutment screw was tightened. Kruskal-Wallis test and Mann–Whitney U test (P < .05) were used to compare different implant-supported zirconia frameworks on each study model.

Results: E-E frameworks had higher vertical deviations (ranged from 40.07 to 131.05 μm) in H35 and H70 error levels as compared to E-NE (ranged from 19.75 to 85.13 μm) and NE-NE (ranged from 6.58 to 14.31 μm) frameworks. Larger vertical deviations were observed in E-NE frameworks than NE-NE frameworks with all levels of the simulated errors except H100 and V150 ones. Comparing medians of the 100 μm error in horizontal (E-NE 140.42 μm; NE-NE 151.62 μm) and vertical (E-NE 49.84 μm; NE-NE 42.56 μm) directions, it was found that the horizontal errors caused larger vertical deviations. The comparison between different abutment combinations revealed a significant difference in each simulated error group (P < .001).

Conclusion and Clinical implications: With an increased level of the simulated implant positioning error, the vertical gap between the implant and abutment increases. Horizontal errors are less tolerated than vertical ones and could be regarded as more detrimental. NE-NE abutment combination was found to tolerate better the different error levels followed by E-NE and E-E combinations.

Disclosure of Interest: None Declared.

Keywords: accuracy, dental implants, screw-retained

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