ABSTRACT
Biocompatibility is often referred to as appropriate host response to biomaterials. The absence of acute adverse effects of oral biomaterials is a result of a wide safety margin of these materials in their hosts. Beyond the safety level of the dose, adverse effects in host(s) or appropriate animal model(s) follows a dose-dependent pattern, that is, the higher the dose of biomaterials, the stronger the adverse effects. Below the safety level of acute adverse reactions, some biomaterials may cause low-dose adverse reactions, for example, hypersensitivity, in a small group of patients. Recent research in endocrine-disrupting chemicals at an extremely low dose, for example, bisphenol A, has given rise to controversies in the safety of some oral biomaterials. Whilst biomaterials do not seem to compromise the life span of human beings, low-dose effects of some oral biomaterials warrant further investigation.
5.1 Introduction and Consensus DefinitionsBiomaterials serve to restore/promote health, function, and/or esthetic appearance of patients. To fulfill such purposes, they are designed to work within their hosts. Such a relationship between biomaterials and host responses has long been loosely described as biocompatibility. The definition of the term “biocompatibility” may resort to highly philosophical and lengthy debates before any agreeable definitions can be arrived at [1]. In other words, this aspect of biomaterials is very confusing. Definitions of the term “biocompatibility” had varied between authorities [2, 3], dictionaries [4-6], encyclopedias [7, 8], personal preferences [1], etc., until 1986, when a consensual definition emerged in a conference held in Chester, UK [9]. The same issue was reassessed in 1991 in a conference, again in Chester, UK, where experts in this issue agreed that their 1986 definition of biocompatibility had stood challenges over the years and should be upheld as the consensual definition of biocompatibility, as follows [10]: Biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific situation [9]. This consensual definition of biocompatibility includes the terms “material” (“biomaterial” to be more precise) and “host response.” The consensual definitions of these two terms had also been drawn in the 1986 Chester conference. A biomaterial is defined as a nonviable material used in a medical device, intended to interact with a biological system [9]. A host response is defined as the reaction of a living system to the presence of a material [9]. These definitions have not ceased to evolve with time. As technology advances and our understanding in biomaterials and host responses expands, the transition from a material-based to an application-based component was suggested for the definition of biocompatibility [11, 12]. After extensive and vigorous discussion in the Chester conference in 1991, the term “biomaterials” was one of the five definitions updated. A biomaterial was redefined as a material intended to interface with biological systems to evaluate, treat, augment, or replace any tissue, organ, or function of the body [10].
