Purpose :The aim of this study was to compare between Monolithic Translucent Zirconia (Y-TZP) and IPS E.max press in marginal fit and fracture strength. Materials and methods, forty ceramic crowns were fabricated, Then divided into 4 groups: Group A: Ten monolithic TZI CAD/CAM zirconia crowns N=10 Group B: Ten monolithic IPS E.max press crowns N=10, Group C: Ten veneered ZI CAD/ CAM zirconia core N=10, Group D: Ten veneered IPS E.max press core N=10,then Each group was subdivided into two subgroups: Subgroup 1: Samples not subjected to thermocycling N=5 as control. Subgroup 2: Samples subjected to thermocycling N=5 The samples were cemented to corresponding epoxy resin dies. The marginal fit was measured and scanned with digital microscope. The fracture strength of the restorations were measured by using universal testing machine with a load 5 KN. The obtained data were collected, tabulated and statistically analyzed. Results: The results of marginal fit showed that the vertical marginal gap values of all groups were within the clinically acceptable range. While the Results of fracture resistance showed that fracture strength of monolithic translucent Y-TZP is (3484.28 N) considerably higher than monolithic IPS E.max press (1515.45 N), followed by veneered ZI zirconia (1483.84 N), and finally veneered IPS E.max press (1091.64 N) after thermocycyling. Conclusions: It was found that veneered crown groups recorded lower gap mean values than monolithic groups. The monolithic crown groups recorded higher fracture load mean values than veneered groups. Monolithic translucent Y-TZP zirconia crowns seem to be a promising treatment alternative, especially for patient with a history of fractured restoration.

Purpose:The purpose of the current study was to evaluate marginal accuracy and color stability of lithium disilicate laminate veneer compared to hybrid ceramic veneer. Materials and Methods: Forty maxillary teeth were collected and prepared (but joint preparation) to receive a laminate veneer. They were equally sub grouped (n= 20) to receive 2 types of laminate veneers (IPS E-max CAD and vita enamic). The veneer was milled from the blocks in a CEREC 3 Machine. All veneers were cemented with resin cement. All samples had been subjected to 20000 thermal cycles which are equivalent twenty years of clinical use. Marginal gap were measured by using universal serial bus (USB) Digital microscope. Colors were measured using a reflective spectrophotometer.Marginal gap and color were measured pre and post thermo cycles. Data were tabulated and statistically analyzed. Results: For the marginal gap, the two tested materials demonstrated an acceptable value. Regarding the color stability there was color change for both groups after thermal cycling with higher mean values for Vita Enamic than E-max and that was statistically insignificant. Conclusion: The E-max veneers recorded less marginal accuracy and more color stability than Vita Enamic and they did not affected by thermo cycling. Codex : 36/1907 azhardentj@azhar.edu.eg