Introduction: Interim prosthesis play an important role in maintaining integrity of abutment tooth till final prosthesis is fabricated. Thus, using different fabrication techniques which can affect the mechanical properties of material can be useful to determine longevity of prosthesis. Aim: To evaluate the marginal gap and Flexural Strength (FS) of Computer-aided Designing/Computer-aided Milling (CAD/CAM) milled, 3D printed and conventional chairside interim 3-unit Fixed Dental Prosthesis (FDP). Materials and Methods: The present in-vitro study conducted in the Department of Prosthodontics, Bharati Vidyapeeth Dental College and Hospital, Sangli, Maharashtra, India, for duration of one year and six months between May 2022 to November 2023, 45 dies were fabricated by 3D printing technique. A total of 45 3-unit fixed dental prosthesis were fabricated over these dies by various techniques i.e., CAD/CAM Milled, 3D Printed and Conventional i.e., 15 sample per group I and J. All samples were cemented on dies under 20 N force and were evaluated for marginal gap with stereomicroscope under 40X magnification and assessed in millimetre (mm). Mean of marginal gap at premolar and molar for each sample was evaluated. Thermocycling was carried out for 5,000 cycles in distilled water (5oC and 55oC) in a digitally controlled water-bath chamber. Universal testing machine was used to evaluate FS using "three-point bend test". One-way ANOVA and Post-hoc Tukey's Honest Significant Difference (HSD) test were used for statistical analysis. Results: On evaluation of marginal gap, a significant difference was noted between the three groups with p-value=0.0006 with 3D printed group showing the most marginal gap. On evaluation of FS, a significant difference was noted between the three groups with p-value=0.0001. On pair-wise comparison, highly statistically significant difference was seen between all groups where CAD/CAM Milled showed greater FS followed by conventional and 3D printed. Conclusion: The CAD/CAM Milled showed better marginal adaptation and greater FS followed by conventional and 3D printed group.
