Enhancing Mechanical and Tribological Enhancing Mechanical and Tribological Properties of 3D-Printed Dental Photopolymer Resin Using Hydroxyapatite Nanoparticles

A novel stereolithography-based three-dimensional (3D) printing technique incorporating hydroxyapatite (HA) nanoparticles into dental photopolymer resin was introduced in this study. The design aimed to address the inadequate mechanical strength of conventional dental photopolymer resins by leveraging the reinforcing properties of HA. The HA concentrations of 0, 1, 3, and 5 wt.% were mixed with the resin to produce four distinct resin-HA (RHA) composites. The composites were evaluated for tensile strength, impact strength, and hardness, wear rate (K), and coefficient of friction (µ). Morphological analysis using scanning electron microscopy (SEM) provided insights into HA distribution and the resulting microstructural changes. The design approach incorporated HA nanoparticles to enhance molecular stiffness and promote a mechanical interlocking effect within the resin matrix. These mechanisms led to significant improvements in the composite's mechanical and tribological properties. The 5 wt.% RHA composite demonstrated the highest tensile strength (66.11 MPa), impact strength (35.2 kJ/m²), and Shore D hardness (79.32). Tribological tests revealed that this composite also exhibited the lowest wear rate and coefficient of friction, correlating with its superior mechanical performance. SEM analysis revealed finer debris and smoother wear tracks in HA-reinforced samples compared to HA-free samples, highlighting the role of HA in improving wear resistance. This study underscores the potential of integrating HA nanoparticles to enhance the performance of 3D-printed dental resins, providing a pathway for developing advanced materials tailored for dental and biomedical applications.