Flexible hydrogel-HA composite, which has a mineral-to-organic matrix ratio approximating that of human<unk> <unk>  refers to<unk> -like material created in a laboratory that can be used in<unk>  grafts, to replace human<unk>  that was lost due to severe fractures, disease, etc.<unk>  fracture, which is a complete or partial break in the<unk> , is a very common condition that has more than three million US cases per year. Human<unk> s have the ability to regenerate themselves by cycle of<unk>  resorption and<unk>  formation. The cell responsible for<unk>  resorption is osteoclast, while the cell responsible for<unk>  formation is osteoblast. That being said, the human body can regenerate fractured<unk> . However, if damage to<unk>  is caused by a disease or severe injury, it becomes difficult for the body to repair itself. When the human body is unable to regenerate the lost<unk>  tissue, surgeons come in and replace the missing<unk>  using autografts, allografts, and synthetic grafts<unk> . When comparing<unk>  to autograft and allograft, it is less invasive and more biocompatible since it avoids the risk of unknown viral infections. The use of solid freeform fabrication in design of composite scaffolds When designing implanted biomaterials, key criteria are biocompatibility, osteoconductivity, high porosity and biomechanics compatibility.<unk>  was initially made of materials like metals and solid ceramics, which are strong enough to sustain the loading in<unk> . However, the rigidity of those materials created an enormous burden on patients and was not consistent with the criteria for implanting biomaterials.<unk> s made of metal and ceramic tend to do poorly in terms of biocompatibility since it is difficult to blend into<unk>  tissues. Thus, to better help those in need to live a more comfortable life, engineers have been developing new techniques to produce and design better<unk>  structure and material. The two major components of<unk>  are hydroxyapatite Ca10(PO4)6(OH)2, and collagen fibers. Hydroxyapatite, which is one of the most stable forms of calcium phosphate, makes up about 60 to 65 percent of the<unk> . The rest of the<unk>  is composed of materials including chondroitin sulfate, keratan sulfate and lipid. Increased research and knowledge regarding the organization, structure of properties of collagen and hydroxyapatite have led to many developments in collagen-based scaffolds in<unk>  tissue engineering. The structure of hydroxyapatite is very similar to that of the original<unk> , and collagen can act as molecular cables and further improve the biocompatibility of the implant.
Artificial bone
Artificial cartilage
Bone cement
Artificial ligament
Artificial organ
Nano-scaffold
Artificial skin
Bioceramic