Development and characterization of a dental PMMA-based biocomposite reinforced with <i>Salvadora persica</i> powder

The present study investigated the effect of Salvadora persica (siwak) powder incorporation on the mechanical and thermal behavior of polymethyl methacrylate (PMMA) denture base resin. PMMA-based biocomposites containing 3 wt%, 5 wt%, and 7 wt% siwak powder were fabricated and evaluated through tensile testing, Young’s modulus determination, Vickers microhardness measurement, and thermogravimetric analysis (TGA). Structural and interfacial characteristics were assessed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The incorporation of siwak powder significantly modified PMMA performance. The 3 wt% composite exhibited the highest tensile strength (∼60 MPa) and elastic modulus (∼3329 MPa), corresponding to increases of approximately 33% and 13%, respectively, relative to unfilled PMMA. Microhardness increased progressively with filler content, reaching 23.50 HV at 7 wt% (∼17% increase). TGA results demonstrated enhanced thermal stability, with an increase in degradation temperature of approximately 35.8°C. FTIR spectra indicated the absence of new chemical bonding, suggesting predominantly physical interactions between filler and matrix, while SEM observations revealed fracture morphology consistent with particle reinforcement. These findings indicate that siwak powder acts as an effective natural reinforcing filler for PMMA, with optimal mechanical enhancement achieved at low filler loading.