EFFECT OF TWO FABRICATION TECHNIQUES (CAD/CAM AND 3D PRINTING) ON THE INTERNAL FIT, MARGINAL ADAPTATION AND FRACTURE RESISTANCE OF MULTIPLE FUSED PROVISIONAL RESTORATIONS. (IN VITRO STUDY)

Aim: To evaluate the internal fit, marginal adaptation, and fracture resistance of multiple fused provisional crowns fabricated using two digital methods; subtractive, and additive techniques.Subjects and methods: Typodont model was used, where mandibular first, second premolars, and first molars were prepared to receive 3 fused provisional crowns, fabricated using two techniques; milling (SM group) and 3D printing (AM group) by digital light processing (DLP) (11 samples per group). Silicone replica technique was used to evaluate the internal gap, while the vertical marginal gap (VMG) was evaluated by direct viewing technique using digital microscope before cementation. Cementation of the crowns over duplicated epoxy resin dies was performed under static load (50 N) then fracture resistance was tested using a universal testing machine. Results: The milled group showed higher internal gap values (102.02 ±11.2 μm) than that of the 3D printed group (100.6 ±13.1 μm) without statistically significant difference. While, the VMG was significantly higher in the SM group (48.58 ± 5.69 µm) than the AM group (43 ± 5.06 µm). Also, the fracture resistance of the SM group (1542.62±214.89 N) was significantly higher than the AM group (774.89 ±170.17 N).Conclusion: The internal and marginal fit of the 3D printed group were better than that of the milled group. However, the milled provisional restorations showed higher fracture resistance