Evaluation of intaglio surface trueness, wear, and fracture resistance of zirconia crown under simulated mastication: a comparative analysis between subtractive and additive manufacturing

Abstract

PURPOSE This in-vitro analysis aimed to compare the intaglio trueness, the antagonist’s wear volume loss, and fracture load of various single-unit zirconia prostheses fabricated by different manufacturing techniques. MATERIALS AND METHODS Zirconia crowns were prepared into four different groups (n = 14 per group) according to the manufacturing techniques and generations of the materials. The intaglio surface trueness (root-mean-square estimates, RMS) of the crown was measured at the marginal, axial, occlusal, and inner surface areas. Half of the specimens were artificially aged in the chewing simulator with 120,000 cycles, and the antagonist’s volume loss after aging was calculated. The fracture load for each crown group was measured before and after hydrothermal aging. The intaglio trueness was evaluated with Welch’s ANOVA and the antagonist’s volume loss was assessed by the Kruskal-Wallis tests. The effects of manufacturing and aging on the fracture resistance of the tested zirconia crowns were determined by two-way ANOVA. RESULTS The trueness analysis of the crown intaglio surfaces showed surface deviation (RMS) within 50 µm, regardless of the manufacturing methods ( P = .053). After simulated mastication, no significant differences in the volume loss of the antagonists were observed among the zirconia groups ( P = .946). The manufacturing methods and simulated chewing had statistically significant effects on the fracture resistance ( P < .001). CONCLUSION The intaglio surface trueness, fracture resistance, and antagonist’s wear volume of the additively manufactured 3Y-TZP crown were clinically acceptable, as compared with those of the 4Y- or 5Y-PSZ crowns produced by subtractive milling.

Fit, Precision, and Trueness of 3D-Printed Zirconia Crowns Compared to Milled Counterparts

“…The greater deviation of the occlusal surface of milled crowns might be related to the number of milling burs and axes or the geometric and diameter limitations of the milling burs [ 33 ]. The trueness findings of this study do not match those reported in the literature [ 9 , 15 , 37 , 55 , 56 ]. The discrepancies detected could be related to differences in the analysis method utilized (absolute average, RMS, or (90°/10°)/2) [ 15 ], scanning device [ 15 , 37 , 55 ], the use of powder spray prior to scanning [ 9 , 37 ], or the number and orientation of support structure during production [ 56 ].…”

Effect of CAD‐CAM restorative materials and scanning aid conditions on the accuracy and time efficiency of intraoral scans

“…Under the NSA conditions, the HC and 3YZ groups showed lower mean RMS values, whereas the M group showed the highest mean RMS value ( P < 0.05). The mean RMS values of all groups, except the HC and 3YZ groups, exceeded the clinically acceptable limit of 50 μm for the CAD‐CAM crown 51–56 . Under PSA and LSA conditions, no significant difference was observed among the materials.…”

Manufacturing and Characterization of Dental Crowns Made of 5-mol% Yttria Stabilized Zirconia by Digital Light Processing

“…From the viewpoint of resolution and accuracy of 3D printing techniques, digital light processing (DLP) and stereolithography (SLA) have been most extensively investigated for the manufacturing of zirconia dental crowns [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. These techniques can selectively photo-cure thin layers of zirconia suspensions, where zirconia particles are uniformly dispersed in photocurable monomers, using high-resolution UV engines according to pre-designed 2D images layer-by-layer [ 3 , 4 ].…”

“…This approach can precisely replicate intricate 3D geometries of dental crowns designed for individual patients [ 3 , 4 ]. In the DLP process, a build platform can move downward to a predetermined position in a vat containing a zirconia suspension, and thus a uniform layer can be formed between the build platform and vat, which can be then photopolymerized by 2D images of UV light [ 7 , 8 , 12 , 13 , 15 , 16 ]. In addition, recoating systems can be integrated into DLP machines (e.g., lithography-based ceramic manufacturing (LCM)), in order to mechanically spread ceramic suspensions uniformly just above the bottom of a vat [ 5 , 14 ].…”

“…In addition, our group recently developed a new type of top-down DLP process by employing specifically designed feeding and recoating systems, where ceramic suspensions can be extruded through a nozzle at a controlled rate and then uniformly spread onto previously photopolymerized layers by a recoater [ 6 ]. A number of recent works have demonstrated that DLP and SLA techniques could offer outstanding dimensional accuracies comparable to CAD/CAM [ 10 , 11 , 12 , 13 , 14 , 15 , 18 ]. However, 3D-printed zirconia objects often suffer from imperfections, including pores within layers and weak interfaces between layers, causing severe reductions in mechanical properties [ 5 , 6 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ] and optical translucency [ 6 , 22 ].…”