Surgical Biomaterials and Tissue Regeneration Technologies (Part 2)

What are biomaterials? A very broad definition of surgical biomaterials may include any substance that has the capacity to function in contact with living tissue and not be rejected by the body. This would include products made from metals, alloys and polyester-based materials such as orthopedic implants, and a number of other products traditionally used for the reconstruction or repair of tissue. The modern definition of surgical biomaterials, however, focuses on substances and products that not only evade rejection by the body, but that can interact with living tissue. These biomaterials do the job they are meant to perform, and then are either absorbed naturally by the body over time and eliminated by biological processes or become a permanent part of the surrounding tissue.

The use of nonviable materials to repair or replace defects in the human body dates back thousands of years. Early civilizations such as the Egyptians, Romans and Aztecs used wood, ivory, gem stones and other objects to replace missing teeth and fill in bone defects more than 2,500 years ago. Since then, scientific developments have led to the use of a number of different synthetics and natural materials in the human body. From World War I through World War II a number of natural rubbers, celluloids, vinyl polymers and polyurethanes were used for grafts, artificial hearts and catheters. During World War II, silicon was used in Japan to enhance the breasts of prostitutes and polymethylmethacrylate (PMMA), the main component in many of today’s bone cements, was used in dental and craniofacial applications. Alloys have been used as pins and plates in the human body since the early nineteenth century. The use of steel and other alloys, which have the tendency to discolor, eventually led to the development and introduction of stainless steel and titanium, materials that are still commonly used in the production of orthopedic implants today.

Biomaterials can be made either from synthetic compounds or natural substances. Synthetic materials such as hydroxyapatite and tricalcium phosphate have been used for years in dental, craneo-maxilofacial and orthopedic procedures. The use of natural substances such as human or animal tissue in the manufacture of surgical biomaterials is a more recent development. A number of years of research and development in this area have led to technological advances in the processing of natural tissue to remove its toxicity and improve its clinical properties. Natural substances generally have complex structures that are difficult to replicate with synthetic compounds, and therefore can interact with human tissue in ways that synthetic products cannot. The ongoing development of surgical biomaterials is now resulting in a number of hybrid products that integrate both natural and synthetic substances in an effort to provide products that offer the clinical benefits of both materials.

Some of the benefits of biomaterials can be seen in their use in surgeries that typically use “autografts”. This is when surgeons take tissue (or bone) from one part of the patient’s body and then place it in another part of their body in order to repair a defect or replace diseased tissue. One of the most common procedures in which autografts are used is spinal fusion, a surgery in which one or more vertebrae of the spine are welded together with the aim of eliminating painful motion. During a spinal fusion, the surgeon makes an incision in the patient’s hip and removes a piece of bone from the pelvis, which is then implanted in the space between the vertebrae and held in place by metal fasteners. The pain and problems associated with motion are reduced over time, as the implanted bone and vertebrae grow into a single, solid bone. Some of the major disadvantages of autografts in these procedures are the additional operating time it takes the surgeon to harvest the graft, the extra postoperative recovery time needed and the added pain the patient must endure at the harvest site. Synthetic or animal based biomaterial bone substitutes provide surgeons and their patients with an option that lessens time under anesthesia and cuts down on recovery time.

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