the allergist for tests of other dental substances that are of potential significance in each case (Gawkrodger, 2005; Amendments (MDA) to the FFDCA included regulation of medical devices, including dental devices, for the first time. The biocompatibility of dental restorative materials is evaluated using compositional analysis, surface degradation tests, cell culture tests, clinical testing in humans, and animal model tests. INTRODUCTION 3 Biocompatibility refers to the study of interaction of various materials with human tissues. The hydrodynamic theory of pulp pain is related to the movement of dentinal fluid and its influence on the odontoblastic processes. In a manner similar to local effects, systemic effects from dental materials are also a function of the distribution of substances released from dental materials. Clearly, one of the primary concerns of any dental practitioner is to avoid harming the patient. These reactions are insensitive to the amount of the allergen that is available or released. Usage tests are equivalent to clinical trials. Estimates of intake levels from air (in micrograms per day) are 0.12 for Hg0, 0.04 for Hg2+, and 0.03 for methyl mercury. It is used in load-bearing hip prostheses and dental implants, because of its combination of excellent corrosion resistance, high wear resistance, high strength, and good biocompatibility. Inflammation adjacent to the metal margin of a metal-ceramic crown. Yet there are profound consequences of this definition for orthodontic practitioners. As indicated previously, teeth with cervical restoration margins can release ions or other substances into the gingival sulcus, and adverse reactions can affect the periodontal attachment and the periodontal ligament (, Schematic illustration of the periodontal attachment area. However, in 2005, the ADA decided to phase out the Seal of Acceptance program for professional products. Although amalgams do not release anywhere near toxic levels of mercury, the long half-life of mercury in the body raises concerns among some individuals. This outward fluid pressure from the pulp chamber toward the enamel is not sufficient to eliminate the inward diffusion of bacteria, bacterial products, or material components into the pulp. A potential allergy to one of the metal components should be explored, since such tissue responses to leached metal ions is one of the most prevalent adverse effects reported by national adverse effect registries. The frequency of litigation as a result of biomaterials causing harm to patients is unclear but is probably low. Finally, the best materials of the initial group are subjected to clinically relevant usage tests prior to decisions on whether or not they will be used for clinical trials in humans. Without the light interaction there is no color. Primary tests measure basic biological properties such as toxicity or mutagenicity of the material. Cast metals solidify first at the investment mold surface, and subsequently, the hottest area solidifies last. More recently, in 1976, Medical Device Amendments (MDA) to the FFDCA included regulation of medical devices, including dental devices, for the first time. Toxic—Capable of causing injury or death, typically by a chemical agent. As biomaterials used in the mouth are su ... read full description. The interactions that occur will depend upon the material, the host, and what forces and conditions are imposed on the material (its function). Class I: Low risk—General Controls [generally exempt from 510(k)], 2. However, fluid exchange most likely occurs, and this may degrade the resin or the collagen network that is incompletely embedded with the resin, thereby reducing the longevity of the dentin–resin bond. Further, the periodontal pocket, or gingival sulcus, may accumulate significant concentrations of leached substances that do not accumulate to these levels in other areas. ); or. Of these test parameters, measurement of mercury in the urine after 24 hours may be the best long-term indicator of the total metallic mercury body burden, normalized to grams of creatinine clearance from the kidneys. However, an observational period may be required to determine if the effect is time limited, such as may have been caused by mechanical trauma or chemical irritation. The mechanisms by which these materials cause problems are not known, but there is evidence that some resin components such as HEMA (hydroxyethyl methacrylate), TEGDMA (triethylene glycol dimethacrylate) and camphoroquinone (Chapter 9) are capable of activating immune cells directly. Thus, it is clear that sufficient data exist to establish a threshold level for a peanut allergy. Which factors come into play to explain these differences? Mercury is not regulated under the Clean Air Act (U.S. Code, Title 42, Chapter 85, signed by President Richard Nixon on December 31, 1970). Yet, the results of such testing are not 100% conclusive. This chapter describes the conceptual aspects of biocompatibility with specific emphasis on the solid and liquid materials of greatest relevance to dentistry. The incidence of nickel allergy in the general population is somewhere between 10% and 20%, being far more common in females than males. Histologically, the inflammatory response is characterized by edema of the tissue caused initially by an infiltration of inflammatory cells such as neutrophils and, later in the chronic stage, to the action of monocytes and lymphocytic cells. by lipopolysaccharide. Schematic illustration of pathways that leached ions or substances may follow during in vivo degradation of a dental restoration (R) into the oral cavity (OC), dentin (D), the pulp chamber and the pulp tissue (P), the periodontium (PD), and periapical tissue and bone (PA). Two biocompatibility-patient safety issues have been prominent in orthodontics in recent years. We often ascribe color to a material, but color is a property not only of the material but also of the interaction of the material with light. 3. ble/ ( -kom-pat´ĭ-b'l ) being harmonious with life; not having toxic or injurious effects on biological function. This specification represented great progress toward the establishment of biological tests for dental materials. If a cobalt-chromium alloy is placed in the same dental implant situation – same host, same placement technique, same load – no osseointegration will occur. Methyl mercury is the most common form that is transformed by natural processes; it is a more toxic form than ethyl mercury (C2H5Hg+) or elemental mercury. Estimates are that several hundred amalgam surfaces would be necessary to achieve these levels. The relationship of dental materials to inflammatory reactions is important because of chronic inflammatory responses such as pulp inflammation and periodontal disease. Photo of a patient’s arm after she tested herself with metal discs made of a nickel–chromium (Ni-Cr) alloy. A third key point about the definition of biocompatibility is that it is not a property only of a material, but of a material interacting with its environment. The dental polymers that is to be used in the oral cavity should be harmless to all oral tissues—gingiva, mucosa, pulp, and bone. However, the concentration of bisphenol A is dependent on the quality standards that the manufacturer follows relative to allowable impurity levels. No test can produce results that can guarantee that a substance will not cause adverse effects in all individuals who are treated with the substance. Evaluations of toxicity are designed to identify adverse health events caused by physical agents, chemical agents, or both. Materials and Methods . It has the same technological characteristics (includes chemistry, materials, design specifications, mechanical, or biological properties, etc. Estrogenicity is the ability of a chemical to act as the hormone estrogen does in the body. The nervous system is sensitive to all forms of mercury, although the brain is most sensitive to metallic mercury and methyl mercury. Toxic dose low (TDLo)—The lowest dose of a substance introduced by any route except inhalation over any given period that has been reported to produce any toxic effect in humans or carcinogenic, neoplastigenic, or teratogenic effects in animals or humans (U.S. National Institute of Occupational Safety and Health). Ingested metallic mercury is poorly absorbed from the gut (0.01%), so the primary portal into the body is through inhalation of mercury vapor. Toxicity—The relative ability (dose-related effect) of a material to cause injury to biological tissues, ranging from improper biochemical function, organ damage, and cell destruction, to death. However, an observational period may be required to determine if the effect is time limited, such as may have been caused by mechanical trauma or chemical irritation. Products that pass the primary tests, such as the toxicity test, then progress to secondary and usage tests (Figure 7-12). As shown in Figure 7-15, incomplete bonding or resin penetration into the collagen mesh of acid-etched dentin can lead to fluid ingress along gaps wider than 1 µm, which is referred to as microleakage. However, in 2005, the ADA decided to phase out the Seal of Acceptance program for professional products. Biocompatibility is also a property of a material interacting with its environment. Very few implant materials or implant coatings promote osseointegration. The practitioner must consider the particular clinical application and patient, and not assume that, because a certain alloy is biologically acceptable as an archwire, it will be acceptable as a bracket or a band or a spring. The biological response to a corrosion process depends on the composition of the material, the amount of the offending species released over time, the shape of the prosthesis, and its location on or within tissues. A properly placed CP (commercially pure) titanium implant or a plasma-sprayed hydroxyapatite-coated (HA-coated) Ti-6Al-4V implant will osseointegrate with mandibular bone over time. This resin layer acts as a partial barrier to the transport of elements, ions, or substances that are released from a variety of restorative materials. When a material is placed in, or in contact with, the human body, it is generally referred to as a biomaterial. This concern is especially important in orthodontic practices where many patients are children or young adults. Because of the biological concerns about mercury, regulators have considered monitoring and restricting the amount of mercury in wastewater from dental practices. Children and fetuses are most sensitive to the effects of mercury on the nervous system. Different types of biological responses to substances can occur in humans. These local effects are a function of (1) the ability of substances to be distributed to these sites, (2) their concentrations, and (3) exposure times, which may range from seconds to years. It is an overview of biocompatibility concepts, terminology, outcome data from national registries of adverse effects, and principles of established test methods. The Dental Products Panel of the U.S. Food and Drug Administration (FDA) Medical Devices Advisory Committee reviews and evaluates data concerning the safety, effectiveness, and regulation of products for use in dentistry, and bone physiology relative to the oral–maxillofacial complex and makes appropriate recommendations to the FDA Commissioner. Their migration to other sites can occur by diffusion through tissues or by flow through lymphatic channels or blood vessels. This interface is active and dynamic, the material breakdown products affect the body, and the body’s environment affects the material’s surface structure. The response of the body to a material can change over time (i.e., it is dynamic), because the body may change through disease or aging; the material may change through corrosion or fatigue, or the loads placed on the material may change through changes in the occlusion. Thus, color is a property of a material interacting with its environment. However, these types of issues are also relevant to the orthodontist. The biocompatibility of a device depends on several factors, including: the chemical and physical nature of its component materials Sjogren et al investigated the Cytotoxicity of Dental Alloys, Metals, and Ceramics Assessed by Millipore Filter, Agar Overlay, and MTT Tests as follows: Statement of problem: Biocompatibility of dental materials is dependent on the release of elements from the materials. n. The property of being biologically compatible by not producing a toxic, injurious, or immunologic response in … The frequency with which nickel elicits adverse responses in sensitive patients through oral exposure is controversial, but rarely can be spectacular. Environmentalists fear that these substances will alter reproductive cycles and developmental processes in wildlife, and there is evidence to support these concerns with regard to humans. Currently, the Dental Devices Branch of the Center for Devices and Radiological Health regulates premarket clearance of dental devices. Bilateral lichenoid lesions that are associated with gold alloy crowns. This mission includes aspects pertaining to dentistry such as fluorosis caused by excess levels of fluoride in drinking water. The +LPS line represents the effect of cell stimulation by lipopolysaccharide while the –LPS line indicates that the monocytes were not stimulated by lipopolysaccharide. The Clean Air Act Amendments were enacted by Congress in 1990 and legislation has made several minor changes since 1990. One such report found that 49% of children had sensitivity to some type of material or food. Is the patient diabetic? Although not common, patients can suffer severe or even fatal allergic reactions to these materials. Which tests can provide conclusive evidence to identify the specific cause of an allergic or toxic response to a restorative material? Still other studies have attempted to look at blood cell types and cell numbers in dentists, who are presumably exposed to higher levels of mercury because of their daily occupational exposure. Biocompatibility is a dynamic, ongoing process, not a static one. Excretion may occur through exhaled vapor or through urine, feces, or skin. www.indiandentalacademy.com Shown schematically in Figure 7-1 are the critical tissue and organ sites that can be affected by exposure to dental restorative materials and auxiliary materials used to make impressions and models. The most common forms of mercury that occur naturally in the environment are metallic mercury, inorganic salts, mercuric sulfide (HgS), mercuric chloride (HgCl2), and methyl mercury (Ch3Hg+). Biomaterials. Biocompatibility is related to the behavior of biomaterials in various contexts. Biocompatibility has also been described as the ability of a material to perform with an appropriate host response in a specific application. Does the patient smoke? Specific dental test substances have been established for this purpose, and the treating dentist may have to make additional suggestions to the allergist for tests of other dental substances that are of potential significance in each case (Gawkrodger, 2005; Khamaysi et al., 2006). J Dent Res 77:1772-1778, 1998; Schmalz and Garhammer, Dent Mater 18:396-406, 2002). REACTIONS OF PULP- Microleakage: If a bond doesn’t form between the tooth and the restorative material or debonding occurs, bacteria, food debris or saliva may be drawn into the gap by capillary action. Sampling of metals in hair, nails, feces, bone, and teeth is also advocated in certain cases. Thus, biocompatibility concerns directly influence regulatory policy. Each biomaterial can degrade and release components under certain environmental and physical conditions. However, these types of issues are also relevant to the orthodontist. The biocompatibility of a dental material is mainly determined by its release of substances through _____ & _____. Thus, the damaging effect of a material, if such an effect occurs, is strongly influenced by the remaining thickness of dentin between the material and the pulp chamber. Testing of dental materials also includes tests for pulp irritation responses, pulp capping effects, endodontic applications, and dental implant performance. This overview is designed to provide a brief review of established concepts to assist dentists and other health care professionals in the conservative selection and use of dental restoratives and auxiliary materials. Latex rubber and its associated proteins are capable of causing severe and sometimes life-threatening allergic reactions in patients. Thus, there is evidence that the biomaterials used by dental practitioners can pose some risk to patients. Also in 1930, the Council established the ADA’s Seal of Acceptance program to promote the safety and effectiveness of dental products. Biocompatibility It is the ability of a material to elicit an appropriate biological response in a given application in the body. It is generally accepted that BPA is released from bis-DMA, which is also used in dental products. In a manner similar to local effects, systemic effects from dental materials are also a function of the distribution of substances released from dental materials. The biocompatibility of a material depends on several factors: 3. Thus, biocompatibility issues are important to the orthodontic practitioner from a legal standpoint. Tests for the safety of restorative dental materials must ensure that a candidate material is nontoxic and unlikely to cause adverse immunological effects. Adverse reactions to dental restorative materials and auxiliary materials include one or more of the following effects: allergic reaction, chemical burn, pulp irritation, pulp damage, thermal injury, tissue irritation, and toxic reaction. The surface characteristics of the material, 6. Other actions the FDA decides are necessary to provide reasonable assurance of safety and effectiveness. The general process of biointegration involves the adaptation of bone or other tissue to the implanted material without any intervening space along the tissue-material interface (see Chapter 20). The relationship of dental materials to inflammatory reactions is important because of chronic inflammatory responses such as pulp inflammation and periodontal disease. Despite markedly elevated blood, plasma, and urine levels of mercury, no renal impairment was noted. this effect has been termed microleakage. 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