Intraoral virtually guided minimally invasive design with an occlusal reduction of 1.5mm, axial reduction will be performed with 6 degrees axial taper and a circumferential chamfer margin of 0.5mm in width and 0.5mm coronal to the gingival margin. A milled guiding occlusal resin template of the teeth will be checked for fitting then fixed using spot etching and will be used to guide the amount of axial reductions and taper degree.

Each scan data of virtually guided preparations will be uploaded to a 3D mesh processing reverse engineering software, then superimposed against the reference virtual preparation using the software's best fit matching algorithm tool. Superimposed 3D data files will be sectioned into 5 different 2D planes: buccolingual, mesiodistal, transverse occlusal, transverse middle, and transverse gingival. Differences will be assessed both qualitatively and quantitively to measure deviations. Quantitative assessment will be expressed with a sign: (+) indicating external deviation or (-) indicating internal deviation. The deviation (+ or -) will be numerically described with mean and standard deviation. Qualitative assessment will be through a color-coded mapping of superimposed images where discrepancies between each test specimen and reference file will be expressed with yellow range of color lines indicating external deviations and cyan range of color lines indicating internal deviations

Four scans will be performed using a calibrated laboratory scanner: each 3D printed master cast with 2 preparations designs, external & intaglio surfaces of monolithic zirconia 3-unit FPDs, monolithic zirconia 3-unit FPDs after it has been seated on each preparation design. The 3D point clouds of all 4 scans will be obtained in STL format. The 3D data of the FPD retainers will be registered to the data obtained from the external surface of the crown using registration module in reverse engineering software. The 3D data of the virtual seating of the intaglio & external surfaces on the preparations will be obtained & margins of the FPD retainers & preparations will be extracted. The software's construct cross-sectional cloud circular command to divide the preparation evenly into curves. Every curve will intersect with the outer edge of the ceramic retainer & margin design of the preparation at 2 points. Distance between these 2 points will be recorded (absolute marginal discrepancy)