Influence of preparation form, luting space setting and cement type on the marginal and internal fit of CAD/CAM crown copings.

To evaluate the influence of two different tooth preparation forms, two luting space settings and two cement types on the marginal and internal adaptation of all-ceramic crown copings produced using Cerec3 CAD/CAM system. Forty working stone dies were made from two metal master casts (1. Tooth 36: with anatomic occlusal reduction, 2. Tooth 36: with flat occlusal reduction). Forty crown copings were milled using Vita In-Ceram 2000 YZ: 20 with an luting space settings of 0 = 100 microm and 20 with -50 = 50 microm. Copings were cemented using two cements (zinc phosphate cement, P21: Panavia21), then embedded and sectioned bucco-lingually and mesio-distally. Widths of marginal and internal gaps were measured using a light microscope at magnification of 40X. Data were submitted to one-way ANOVA, and statistical significance was set at p < 0.05. Copings with flat occlusal reduction and luting space settings of 100 pm had a better internal and marginal fit compared with copings with anatomic occlusal reduction and luting space settings of 50 microm, regardless of the cement used. P21 showed a significantly better fit compared with zinc phosphate cement. The presented Cerec3 CAD/CAM system can provide a marginal and internal adaptation which is comparable to that of conventional cast and conventional all-ceramic crowns.