Effect of Fiber and Metal Reinforcement on the Flexural Properties of Printed and Conventional Provisional Restorative Materials

(1) Background: Provisional restorations play a crucial role in maintaining oral function and must exhibit adequate mechanical properties, particularly fracture resistance, to ensure structural integrity throughout the provisional phase. The aim of this study was to compare the flexural strength and modulus of materials used for provisional dental prostheses, with and without fiber or metal reinforcement. (2) Methods: Standardized specimens (2 × 2 × 25 mm) were fabricated from an acrylic resin (Unifast LC), a 3D-printed resin (NextDent C&B), and a bis-acryl resin (Luxatemp Fluorescence). For each material, four experimental subgroups were established: no reinforcement, two types of glass fiber reinforcement (EverStick C&B and EverStick Post NET), and metal reinforcement. Specimens were subjected to a three-point bending test. Flexural strength and flexural modulus were analyzed using a two-way, non-parametric ANOVA with the aligned rank transform. The significance level was set at 0.05. (3) Results: Material type and reinforcement strategy significantly affected flexural strength and flexural modulus. Fiber reinforcement with EverStick C&B yielded the highest values across all materials, particularly in the acrylic resin. Metal reinforcement showed moderate improvements, whereas EverStick NET had limited or no effect and reduced strength in the bis-acryl resin. Reinforced specimens exhibited altered fracture behavior, preventing complete separation after failure. (4) Conclusions: Fiber reinforcement, particularly with EverStick C&B, significantly enhances the flexural strength and modulus of provisional materials. The reinforcement performance is dependent on its type and material interaction, modifying fracture behavior by preventing complete separation.