الفهرس 
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Abstract
The aim of this in vitro study is to compare the marginal fit, color stability, and fracture resistance of temporary bridges constructed by CAD/CAM, 3D printer, and conventional method. Twenty one fixed-fixed temporary bridges were manufactured by three different techniques CAD/CAM (group A), 3D printing (group B), and Conventional method (group C), seven in each group. The vertical marginal gap of each retainer was measured on its corresponding die before cementation. The temporary bridges were analyzed with a stereomicroscope at 6 surfaces (3 in the molar abutment and 3 in the premolar abutment) excluding the surfaces toward the pontic side using a fixed magnification of 40X. Then, all temporary bridges were photographed with a professional digital camera, and the vertical marginal gap measurements were recorded in micrometers (µm). The temporary bridges were cemented using Temp Bond NE cement, then the vertical marginal gap was measured. The results of the vertical marginal gap before cementation showed a statistically significant difference between the three groups. group C (conventional) showed a higher mean vertical marginal gap of 120.42±6.95 μm than group A (CAD/CAM) 68.98±9.93 μm and group B (3D Printing) 52.28±6.32μm. While after cementation, the highest mean value was reported with group C 216.6±14.15 μm, and no statistically significant difference between group A 117.75±5.57 μm and group B 120.25±7.34 μm. The color stability of the three groups was evaluated and baseline color was measured using Vita easy shade intraoral spectrophotometer, then all bridges were thermocycled for 3000 cycles by altering the temperature between 5°c and 55°c with a dwell time of 20 seconds and 10 seconds of transfer time. The color difference values (ΔE) after thermocycling were measured. The results showed a statistically significant difference in mean ΔE between the three groups. group A had the lowest mean ΔE of 2.60±0.28 followed by group B with a mean ΔE of 4.40±0.19 while group C had the highest mean ΔE of 6.02±0.46. The temporary bridges of the three groups were tested for fracture resistance using a universal testing machine. The fracture point and fragment separation also were recorded visually for all samples. The results showed a statistically significant difference between the three groups. group A had the highest mean fracture resistance of 1086.0±39.75 N, followed by group B of 823.0±37.92 N, and group C showed the lowest mean fracture resistance of 493.80±22.48 N. group A and group C were not fractured but they were cracked at the mesial connector area and through the pontic without complete separation of the bridges, while group B was catastrophically fractured into several pieces.