Abstract

When placing a solid material in a biological system, a biological reaction develops against it. This reaction varies in terms of intensity and time depending partially on material type. The term surface energy refers to the energy of the outer most atomic constitution of a material surface that can be estimated by calculating the critical surface tension of the surface. Theta surface refers to the outer most atomic constitution least retentive to glycoprotein which is measured through critical surface tension to be within the range of 20-30 mN/m. For applications require strong biological adhesion, the materials need to have higher surface energy than theta surface range. After implant, the material surface provokes a sequence of biological reactions eventually leading to biofilm development. Surprisingly, what is known as Oppenheimer effect shows an unexpected behavior of foreign body reaction to materials with different ranges of surface energy implanted in rats and mice. This unique behavior is still a big challenge to be explained. The yet unsolved phenomenon is the reason behind implanting a plastic sheet or film that induces sarcoma in rats while implanting the same material in the form of textile or powder induces almost no sarcoma. This review will focus on some various explanations based on historic and recent experimental work.