الفهرس 
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Abstract
The principal aim of this investigation was to evaluate the effect of different labial margin designs (Knife Edge, Collarless and Butt Joint) together with different luting agents (Zinc Phosphate, Ketac Cem and Rely X Unicem) on the vertical marginal gap before and after cementation and coronal microleakage of ceramometalic restoration.
45 intact caries free recently extracted human molars were selected with approximate similarity in size and shape. They were machined cut stimulating the prepared molar of 6mm length, 6.5 mm cervical diameter and 6º Cervico-occlusal angle.
The wax pattern was fabricated by the aid of specially designed copper counter die
Wax pattern were built up on the working die according to labial margin design into three different coping designs;
1- 15 Copings with wide cervical knife edge
2- 15 Collarless Copings
3- 15 Butted margin Copings.
After spruing, investing, casting and finishing, porcelain was applied, condensed and fired according to manufacturer’s instructions. Porcelain application technique is the same for knife edge and butt margin while with collarless crowns direct lift up technique was used.
The vertical marginal gap of samples was measured using (High resolution digital microscope with a fixed magnification of 65X
Restoration were cemented to their corresponding prepared teeth using three different luting agents as follow
45 Samples were equally divided into three groups (15 Sample Each) according to type of labial design margin and every group has been devided to three subgroups (5 Samples each) according to the type of cement used.
A device was designed to perform a constant static load of 5 Kg on the samples to ensure accurate and precise seating of the samples
The vertical marginal gap was measured again after the cementation procedure.
The samples were immersed in a 2% Methylene Blue solution and sectioned in midplane and the coronal microleakage was measured using high resolution digital microscope with a fixed magnification of 65X
The data of the vertical marginal gap and coronal microleakage were collected, tabulated and statistically analyzed to detect any significant values among the different groups