Abstract
Purpose: The aim of this in vitro study was to evaluate the three-dimensional trueness and margin quality of monolithic zirconia restorations fabricated by additive 3D gel deposition, compared with those by
subtractive milling.
Methods: Ten single crowns and ten 4-unit FPDs of different occlusal geometries and margin thickness
were fabricated by additive 3D gel deposition (additive group) and subtractive milling (subtractive group).
An intraoral scanner was used to digitalize the restorations. 3D deviation analysis was applied and root
mean square (RMS) was used to assess the trueness. Margin quality was characterized using optical stereomicroscopy and 3D laser scanning microscopy.
Results: For single crowns with shallow fossae and grooves and normal margin, RMS value of additive
group and subtractive group showed no significant difference in external surface, while additive group
showed higher RMS value in intaglio surface. As for 4-unit FPDs with deep fossae and grooves and thin
margin, RMS value of additive group in external surface was significantly lower than that of subtractive
group and in intaglio surface there was no significant difference between two groups. With a 0.5 mm
chamfer design, single crowns in additive group showed flawless margin with a smooth contour line,
whereas minor flaws could be observed in 4-unit FPDs with thin margin. In subtractive group, restorations showed minor flaws or defects of various number and severity.
Conclusions: Monolithic zirconia restorations fabricated by additive 3D gel deposition have comparable
trueness and better margin quality than those fabricated by subtractive milling. Besides it is more capable
of enabling complex geometry.
