Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings

Abstract

This study evaluated the effect of different parameters on the marginal precision of CAD/CAM-fabricated zirconia copings. Specimens (n=60) were fabricated with two different scanners and two milling systems. The copings were evaluated with respect to their mean and average maximum marginal gaps. A two-way analysis of variance (ANOVA) (α=0.05) was used to evaluate the effect of different parameters (scanner, milling process) on marginal accuracy. The mean (averaged maximum) marginal gaps ranged from 57.9 (112.2 μm) to 71.0 (144.6 μm) in the "as machined" state. After manual adaptation, the respective values ranged from 54.6 (98.0 μm) to 59.9 (107.7 μm). The system and manual adaptation variables were found both to have multiple signifi cant effects on the marginal gap size and to have a complex interaction. Thus, synchronized/validated processing chains should be preferentially used to guarantee optimal fi tting accuracy for CAD/CAM zirconia restorations.

Fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia

“…In experiments performed similarly to our experiment, researchers reported marginal gaps in zirconia frames loaded onto the maxillary second molar of 57 to 71 μm 19) , and they also found that zirconia frames for the mandibular first molar, which were made by milling a completely sintered zirconia block using a CAD/CAM system, had marginal gaps of 18 to 58 μm and internal gaps of 105 to 120 μm 20) . The marginal gap values (48.9 to 59.4 μm) and the internal gap values (125.6 to 139.5 μm) obtained in our experiment were close to the results reported in those studies.…”

Fracture load of ceramic restorations after fatigue loading

“…A previous study demonstrated that the fit of a ceramic restoration may be affected by the milling machine. 26 Perhaps the variation in cement thickness can be attributed to the accuracy of the milling machines. Another limitation in this study is that zirconia restorations did not undergo accelerated aging.…”

A systematic review of CAD/CAM fit restoration evaluations

“…Numerous publications report the adaptation of crown copings made of different materials with an absolute marginal gap ranging from 10 to 110·31 ± 7·22 μm , often with results less than 80 µm . Similarly, the internal gap is between 23·5 ± 7·7 μm and 154·1 ± 10·4 μm in the part axial and between 45·2 ± 15·5 μm and 219.12 ± 87.24 μm in the part occlusal.…”