Hydroxyapatite (HAp) is a highly biocompatible material that has been extensively studied over the past 25 to 30 years and is widely utilized in orthopedic and dental applications. In particular, ultra-fine particle-sized HAp offers greater versatility compared to conventional particle-sized products, making it suitable for a variety of applications such as cosmetic ingredients, composite fillers, enamel restoration materials, and drug delivery systems.