The effect of multicolored machinable ceramics on the esthetics of all-ceramic crowns

Statement of problem. Computer-aided design/computer-assisted machining systems offer the possibility of fabricating restorations from one machinable ceramic block. Whether multishaded blocks improve esthetic results and are a viable alternative to individually stained ceramics has not been fully determined. Purpose. The aim of this investigation was to examine the effect of multishaded blocks on the esthetic appearance of all-ceramic CERIC crowns and compare these crowns with single-shade and stained restorations. Material and methods. Ten subjects were included in this study. For each subject, 6 different crowns were milled with the use of a CEREC machine. One crown was milled from each of the following machinable ceramic materials: CEREC Vitablocs Mark II in classic colors; Vitablocs Mark II in 3D-Master colors; Vitablocs Mark II in either classic or 3D-Master colors, with additional staining; Megadenta Bloxx multishaded; Mark II experimental multilayer; and an experimental multilayer leucite ceramic. Three independent examiners assessed the esthetic appearance of crowns fabricated to match each subject's anterior tooth shade. A scale of 1 to 6 was used to score the shade match and esthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 serving as the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analyzed with the Wilcoxon signed rank test (Pless than or equal to.05). Results. Only individually stained Mark II restorations achieved a mean score below the threshold of 3.5 for all 10 subjects. These restorations were significantly more esthetic (Pless than or equal to.05) than restorations fabricated from all other materials except the Mark II experimental multilayer ceramic. The second best results were obtained for crowns made from single-shaded Mark II 3D-Master blocks: 6 out of 10 restorations were scored below 3.5. Two of the layered materials (Mark II experimental and Bloxx) followed with 5 acceptable restorations out of 10 . Conclusion. Within the limitations of this study, the results provide no evidence that multicolored machinable ceramics improve the esthetics of all-ceramic crowns.