Comparison the marginal and internal fitness of veneered and anatomical zirconia crowns milled by two different CAD/CAM systems (An in Vitro Study)

Abstract

Background: Accuracy of fit is considered a very important factor in a crown fabricating procedure. Zirconium oxide ceramic is gaining popularity because of its remarkable mechanical capabilities and the potential aesthetic results obtained by using its recommended veneering porcelain, this study aimed to determine the effect of porcelain veneering on the marginal and internal fitness of zirconium-oxide crowns milled with two different CAD/CAM systems ( Wet and dry milling).
 Materials and methods: An ideal prepared tooth #16 to receive an all-ceramic crown restoration with 0.8mm chamfer finishing line was used as a master die. It duplicated and poured to get thirty-two stone working dies. The stone dies divided into two major groups according to the CAD/CAM systems being used, then each group subdivided into two subgroups (n=8) either zirconia crowns milled to full contour or traditional veneered zirconia crowns. Each crown then cemented to it stone die and sectioned longitudinally into four pieces. Stereomicroscope with aid of (image J) was used to examine the sample at a magnification of (140X). Four points of measurement were selected at each of the four-sectioned parts.
 Results: The final internal gap value of each sample was the arithmetical mean of the selected points of the four-sectioned pieces The data was evaluated statistically, using One-way ANOVA and LSD tests which revealed highly significant differences (p<0.001) among groups.
 Conclusion: Full-contoured zirconia crowns have better marginal and internal fit than the traditionally veneered crown, (CEREC AC, Sirona) system showed the best internal fitness. The mean gap of all groups was within the clinically acceptance.