Effect of Kenaf Fiber Reinforcement on the Flexural Strength of Pmma-Based Temporary Crown and Bridge Material: An in-vitro Study

Abstract

Purpose: To evaluate the effect of kenaf (Hibiscus cannabinus L.) fiber reinforcement on the flexural strength and yield behavior of polymethyl methacrylate (PMMA)-based temporary crown and bridge material. Materials and Methods: Pretreated kenaf fibers (6 mm length) were incorporated at 2 wt% into a self-cure PMMA provisional material (DPI Self-Cure Tooth Moulding Material, DPI, Mumbai, India). Rectangular specimens (65 × 10 × 3 mm; n = 10 per group) conforming to ADA Specification No. 12 were fabricated for two groups: Group A (unmodified PMMA control) and Group B (kenaf-reinforced PMMA). Three-point flexural testing (span 32.5mm, crosshead speed 2 mm/min) was performed on a universal testing machine. Flexural strength and 0.2% offset yield stress were calculated and compared using an independent t-test (α = 0.05). Results: The kenaf-reinforced group exhibited marginally lower mean flexural strength (70.04 ± 6.60 MPa) compared to the control (71.99 ± 11.06 MPa), with no statistically significant difference (p =0.638). The 0.2% offset yield stress for Group B (59.35 ± 10.83 MPa) was marginally higher than Group A (58.02 ± 5.75 MPa), but this difference was also not statistically significant (p = 0.760). Conclusion: Incorporation of 2 wt% kenaf fibers did not significantly enhance flexural strength or yield resistance of PMMA provisional material. Further investigation with optimized fiber surface treatment, concentration, and orientation is warranted to achieve clinically meaningful mechanical improvements.