Trueness and adaptation of screw-retained implant-supported monolithic zirconia crowns fabricated using 3-dimensional gel deposition.

Statement of problem: Implant-supported monolithic zirconia restorations manufactured using the additive 3-dimensional (3D) gel deposition technique have been introduced. However, studies determining the trueness and adaptation of implant-supported crowns made with the technique are lacking.

Purpose: The purpose of this in vitro study was to evaluate the trueness and adaptation of implant-supported zirconia crowns fabricated using additive 3D gel deposition in comparison with zirconia crowns made with the widely used subtractive milling technique.

Material and methods: Crowns were fabricated for wide-diameter titanium implants and wide-neck abutments. Self-glazed zirconia (SGZ) crowns were fabricated using 3D gel deposition (n=10) and from 2 brands of zirconia blanks, Wieland and Upcera, using subtractive milling (WMZ and UMZ, n=10). All crowns were digitalized by a scanner, and then 3D deviation analysis was applied. The trueness was assessed by root mean square (RMS). Marginal and internal adaptations were evaluated using the direct-view technique (DT) and replica technique (RT). The results were analyzed by using the 1-way ANOVA and Kruskal-Wallis statistical tests (α=.05).

Results: The RMS and marginal discrepancy of SGZ exhibited the lowest values among the 3 groups (P<.05), and the 2 types of milled zirconia crowns had comparable RMS and marginal discrepancy values (P>.05). The internal discrepancy values of SGZ were significantly lower than those of WMZ and UMZ in all regions (P<.05). Compared with the WMZ, UMZ showed comparable internal discrepancy values in the axial and axio-occlusal transition regions (P>.05) but had significantly lower internal discrepancy value in the occlusal region (P<.05).

Conclusions: The adaptation of 3 types of wide-diameter implant-supported zirconia crowns can meet the clinical requirements. Compared with the subtractive milling process, 3D gel deposition produced implant-supported zirconia crowns with improved trueness and adaptation.