Evaluation of hydroxyapatite film by powder jet deposition after artificial aging

This study aimed to create a thick hydroxyapatite (HAp) film on the surface of a human tooth by using a newly developed powder jet deposition (PJD) device for dental handpieces, and sought to examine the microstructural and mechanical properties of the resulting HAp film. The film was evaluated on three-dimensional view, surface roughness, Vickers hardness, and bonding strength before and after artificial aging through thermal cycling (5-55°C) for 500 cycles (30 sec for each cycle, 20 sec of dwell time). The HAp particles in the deposited film were densely packed, and the HAp film's three-dimensional microstructure and its rough surface were maintained after thermal cycling. There was no significant difference in either the HAp film's Vickers hardness or the bonding strength between the film and the enamel substrate before and after thermal cycling. The HAp films created in this study demonstrated excellent microstructural and mechanical properties even after the application of thermal stress. We demonstrated the possibility of using a new type of powder jet deposition (PJD) method we developed to form a new type of interface between the tooth and biomaterials. Consequently, we propose the use of this method in new dental treatments.