Medical grade silicone is silicone with properties that allow it to be safely used in contact with living tissue, a characteristic called biocompatibility. Silicones are a group of synthetic polymers used in many medical devices due to their flexibility, heat resistance, and low toxicity and chemical reactivity. Medical grade silicone is used in medical devices such as bandages, feeding tubes, and medical implants. It can also be used in other products that come into close contact with the user, such as menstrual cups and barrier contraceptives.
All silicones are polymers with a backbone made from a chain of alternating silicon and oxygen atoms, with each silicon atom bonded to the oxygen atoms immediately before and after it in the chain and vice versa for each oxygen atom. Each silicon atom is also bonded to two organic side groups containing carbon, hydrogen, and in some cases other elements as well. Some silicone polymers have side groups and are able to bond with more than one silicon atom, creating even larger molecules composed of multiple linked chains. Silicones vary in their physical and chemical properties and in their suitability for medical use, according to their composition and structure.
Biocompatibility is a material's ability to be used as part of a medical device without harmful effects on the patient. Many materials are unsuitable for medical use due to toxicity or chemical reactivity or because they trigger an immune response in the patient's body. A material's biocompatibility can vary according to application, as materials can affect different parts of the body in different ways. Medical grade silicone is manufactured in carefully controlled environments to prevent contamination with other materials that could compromise the biocompatibility of the final product.
In the United States of America, standards for medical products are established by an organization called the United States Pharmacopeia (USP), which publishes a yearly set of quality and purity standards of the same name. Many other countries also use USP standards, in whole or in part. Medical grade silicone generally refers to silicone classified as USP Class 5 or Class 6, meaning that it has undergone and passed a battery of tests intended to determine whether a substance with biological materials is safe enough to fulfill USP standards for medical use. These classifications by themselves are not proof that a silicone is appropriate for a particular medical application, as a medical device's biocompatibility is always relative to the type of tissues it interacts with.
Medical grade silicone is used for a variety of purposes in medicine. Silicone rubber, which is very flexible and easily shaped, is used for medical tubing in devices such as catheters and in seals. Many implanted medical devices contain silicone components, including pacemakers and artificial joints. Silicone is also used in cosmetic and reconstructive surgery.