Eco-friendly reinforcement of dental composites with poly(methyl methacrylate) and hydroxyapatite synthesized from eggshell waste.

Objectives: Hydroxyapatite (HAp), owing to its chemical similarity to enamel and bone, can enhance the bioactivity, biocompatibility, and antibacterial performance of poly(methyl methacrylate) (PMMA). This study aimed to develop and characterize a sustainable dental biocomposite by reinforcing PMMA with HAp synthesized from eggshell waste, with the objective of improving its mechanical and thermal performance while maintaining biocompatibility.

Methods: HAp was synthesized from eggshells via wet chemical precipitation followed by calcination. The resulting powder was incorporated into PMMA at 10, 20, and 30 wt% fractions. Composites were evaluated using Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Mechanical properties were assessed under tensile and compressive loading.

Results: The synthesized HAp exhibited high purity and crystallinity. The composite containing 10 wt% HAp demonstrated the most balanced performance, with higher glass transition temperature, enhanced thermal stability, and improved tensile and compressive strength compared to pure PMMA. SEM analysis confirmed more homogeneous dispersion at low filler concentrations, while higher loadings (20-30 wt%) led to agglomeration and reduced performance.

Significance: Clinically, the optimized composite (10 wt% HAp) offers enhanced strength, durability, and thermal stability while maintaining biocompatibility, making it promising for dental prostheses, denture bases, and repair resins. This eco-friendly approach valorizes eggshell waste into a functional bioactive filler, supporting the advancement of sustainable dentistry.