Evaluation of the fabrication trueness and internal fit of additively manufactured two-piece zirconia abutments with different build orientations compared to subtractively manufactured abutments

Abstract

Objective

To evaluate the effect of build orientation on the fabrication trueness and fit of additively manufactured 2-piece zirconia abutments when compared with those manufactured subtractively in 3 mol% and 4 mol% yttria-stabilized zirconia (3Y-TZP and 4Y-TZP).

Methods

A titanium-base (Ti-base) abutment was digitized with a scan body and an industrial scanner to design a 2-piece zirconia abutment with a 50 µm cement gap. This design was used to manufacture zirconia abutments additively in different orientations (0-degree, AM-0; 15-degree, AM-15; 30-degree, AM-30; 45-degree, AM-45; 180-degree, AM-180) and subtractively from 3Y-TZP and 4Y-TZP (SM-3 and SM-4) (n=5). An intraoral scanner was used to digitize all abutments, when they were seated on the Ti-base, and only the Ti-base. Abutments’ trueness (overall, external, intaglio, and marginal) was analyzed with the root mean square (RMS) method, and their fit was assessed with the triple-scan protocol. Data were analyzed with 1-way analysis of variance and Tamhane's T2 tests (α = 0.05).

Results

SM-3 abutments had the lowest overall and external RMS (P ≤ 0.023). SM-3 and SM-4 abutments mostly had lower intaglio and AM-0 abutments mostly had lower gingival RMS (P ≤ 0.013). Except for AM-0 and SM-3 (P ≥ 0.930), SM-4 abutments had the lowest average gaps (P ≤ 0.041).

Conclusions

SM-3 abutments mostly had higher fabrication trueness, while AM-0 abutments had trueness similar to or higher than the other additively manufactured abutments. AM-0, SM-3, and SM-4 abutments had similar fit with average gaps lower than 50 µm.