There is a need to reconstruct damaged hard tissue for several reasons that include traumatic or non-traumatic events, congenital abnormalities, or disease. Damaged tissues stemming from these events can become a major issue in orthopedic, dental, and maxillofacial surgery. A study on numerous biomaterials revealed that calcium phosphates had been used in hard tissues reconstruction for more than 6 decades. Hydroxyapatite (HA) was the primary material used in orthopedics and dentistry. Hydroxyapatite (HA) is an inorganic mineral that has a typical apatite lattice structure as (A10(BO4)6C2) where A, B, and C are defined by Ca, PO4, and OH. Pure HA contains 39.68% by weight calcium and 18% by weight phosphorus resulting in a Ca/P mole ratio of 1.67. In fact, there are commercial HA products with Ca/P ratio bigger or smaller than 1.67. The variety in Ca/P ratio indicates the phase shift between tricalcium phosphate (TCP) and calcium oxide (CaO). HA with Ca/P ratio bigger than 1.67 comprises more CaO than TCP and vice versa[1][2]. HA crystals present in the human body both inside bone and teeth. In term of human bone, the HA crystals as a bioactive ceramic cover 65 to 70% by weight of the bone. Furthermore, the architecture of the bone comprises of type-I collagen as an organic component and the HA as an inorganic component. These 2 components form a composite structure at the nanoscale, in which nano-HA is interspersed in the collagen network. This composite forms mineralized collagen and is the precursor of biological mineralized tissue from tendons and skin to hard mineralized tissues such as bone and teeth. Moreover, in the bone, the HA crystals present in the shape of plates or needles, are about 40 to 60 nm long, 20 nm wide, and 1.5 to 5 nm thick[3]. The arrangement of different HA crystalline sizes and shapes provides support for this tissue structural stability, hardness, and function[4][5]. With regard to the dental role of HA crystal, it covers 70 to 80% by weight of dentin and enamel. Within the human body, the enamel is the hardest substance consisting of relatively large HA crystals (25 nm thick, 40 to 120 nm wide, 160 to 1000 nm long)[6]. Different from bone, enamel does not contain collagen. Amelogenins and enamelins replace the function of collagen by providing a framework for mineralization. Besides, HA is the main material of enamel that screens the diffuse reflectivity of light by covering the pores on the enamel surface, thus makes the appearances of enamel is semitranslucent[4][7]. Overall, the pressure-point in hard tissue reparation is on HA due to its chemical proportion that occupies the majority of hard tissue composition, and also its mechanical properties that support the tissue integrity[8]. Currently, HA is widely used as implant material due to its excellent osteoconductive property that supports osseointegration and osteogenesis processes. The biological response to HA implants is influenced by its raw-materials and synthesis process that make product properties vary.