Cast metals solidify first at the investment mold surface, and subsequently, the hottest area solidifies last. Tests for the safety of restorative dental materials must ensure that a candidate material is nontoxic and unlikely to cause adverse immunological effects. For example, a strain of bacteria may be used to assess the ability of a material to cause mutations (the so-called Ames test) or a strai/>, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window). Figure 7-14 shows a graph of the amount of tumor necrosis factor alpha (TNF-α) secreted by monocytes after exposure to hydroxyethyl methacrylate (HEMA) in different concentrations. Toxic—Capable of causing injury or death, typically by a chemical agent. Estimates of intake levels from air (in micrograms per day) are 0.12 for Hg, Numerous studies have attempted to determine whether mercury exposure from dental restorations or other sources contributes to any documentable health problem. Your total health and satisfaction with your dental experience is important to us. Other actions the FDA decides are necessary to provide reasonable assurance of safety and effectiveness. Thus, biocompatibility concerns directly influence regulatory policy. Many individuals have sensitivities to certain chemicals and other environmental factors that need to be taken into account before using a specific dental … The gap also promotes material breakdown along the unsupported margin. There are extremely sensitive methods for detecting mercury in parts per trillion; these methods have made it possible to analyze the sources of mercury exposure for humans. Acute toxicity—Adverse response to a substance that causes ill effects relatively soon after a single exposure or after multiple exposures over a relatively short time (usually less than 2 weeks). Reference dose (RfD)—An Environmental Protection Agency (EPA) estimate, with uncertainty or safety factors built in, of the daily lifetime dose of a substance that is unlikely to cause harm in humans (U.S. Agency for Toxic Substances and Disease Registry). Their migration to other sites can occur by diffusion through tissues or by flow through lymphatic channels or blood vessels. When such products are released to the profession, dentists, dental staff, and patients must assume that sufficient safety testing has been performed to minimize potential risks. Water probably contributes about 0.05 µg/day and food about 20.0 µg/day in the form of Hg2+. If the resin penetrates the collagen network of dentin but does not penetrate it completely, then a much smaller gap (less than 0.1 µm in most cases) will exist between the mineralized matrix of dentin and the collagen–resin hybrid layer (see Figure 7-15). Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), This chapter describes the conceptual aspects of, There are many types of tests for biocompatibility. (Schmalz and Arenhold-Bindslev, 2009, Springer-Verlag, Berlin-Heidlburg). Three major factors are linked to the success of dental materials: (1) material properties, (2) the design of the dental device, and (3) the biocompatibility of component materials. The term refers to the ability of a material to perform with an appropriate host response in a specific situation. At chronic exposure levels, the symptoms are more subtle and include weakness, fatigue, anorexia, weight loss, insomnia, irritability, shyness, dizziness, and tremors in the extremities or the eyelids. These regulations are, for the most part, designed to minimize risks to dental personnel from agents in dental restorative materials and devices. Because the cervical margins of many dental restorations are near the periodontal attachment area (see, If the resin material does not penetrate the collagenous network or debonds from it as the resin shrinks during polymerization, a microscopic gap will form between the resin and dentin. Objective . 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. www.indiandentalacademy.com ISSUES IN DENTISTRY A. LATEX B.NICKEL C. MERCURY AND AMALGAM. Instead, a decision was made to publish a product evaluation newsletter for ADA member dentists that focused on a specific category of professional products in each article. Monocytes control chronic inflammatory and immune responses, and they also secrete many substances that alter the actions of other cells. Dentists must rely on the appropriate test methods that are required in standards and in legal regulations and assume that sufficient evidence of safety has been established for dental devices once they have been cleared for market use. For metals, a rough surface promotes corrosion, which increases the release of ions that may lead to adverse effects. Erythematous reaction sites. Any biomaterial that is placed adjacent to a natural tissue in the body can induce local or systemic biological effects. Fig. biocompatibility: [ bi″o-kom-pat″ĭ-bil´ĭ-te ] the quality of not having toxic or injurious effects on biological systems. The significance of this effect is that relatively small amounts of HEMA released from bonding adhesives or resin-based composites can alter the normal functions of monocytes, thereby contributing to the potential immunotoxicity of some resin-based products. If one has a dental implant that is fully osseointegrated into bone today, does that mean that it will remain osseointegrated over time? Primary tests measure basic biological properties such as toxicity or mutagenicity of the material. 10. 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. It is the practitioner’s problem to decide whether this evidence has merit and to assess the risks of these issues in his or her own practice. biocompatibility of dental materials following International Standard ISO 7405, Dentistry - biocompatibility of medical devices used in dentistry. Evaluations of toxicity are designed to identify adverse health events caused by physical agents, chemical agents, or both. The types and locations of patient tissues that will be exposed to the device, 5. Dental devices, which are not specifically exempted, are required to be cleared by FDA prior to distribution into interstate commerce. The nervous system is sensitive to all forms of mercury, although the brain is most sensitive to metallic mercury and methyl mercury. Unfortunately, assessment of the bio-compatibility of a material is a complicated matter that involves several sophisticated types of biological tests, tests of physical properties such as corrosion, and risk-benefit analysis. Biocompatibility is the most commonly used term to describe appropriate biological requirements of a biomaterial or biomaterials used in a medical device. The transformative ability of mercury can be either helpful or harmful. The most common pathway to market for medical devices. However, there are no similar types of data for comparative evaluations of dose effects on the severity of allergic reactions to restorative materials. One study in Sweden reported that 15% of dentists (vs. 9% in the general population) had itching on the hands in response to gloves, particularly latex gloves. However, if bis-DMA is used, the amount released after placement of a restorative filling is too small to be of concern. 1. adverse reactions reported to all classes of dental materials 2. hypersensitivity, contact sensitivity, and estrogenicity The word biocompatibility refers to the interaction of a living system or tissue with a finished medical device or component materials. One in vitro study revealed less leakage for amalgam restorations compared with resin-bonded composites (Őzer et al., 2002). However, these types of issues are also relevant to the orthodontist. The primary risk for the dental team in orthodontics appears to be contact with latex-based and resin-based materials. Mercury leaves the body by excretion through urine and feces. A critical adverse effect is the first event that is observed at the lowest exposure level. The corrosion properties of the archwires may be different (Chapter 4). The principal concept of immunotoxicity is that substances leached from materials can alter immune system cells, resulting in enormous biological consequences because of the amplifying nature of immune cells. These include inflammatory, allergic, toxic, and mutagenic reactions. 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. Class III: High risk—General Controls & Premarket Approval (PMA) Application (PMA required; must demonstrate safety and effectiveness without relying on a predicate device). Although it is unlikely that the practicing orthodontist will need to evaluate results of these tests directly, it is important that he or she understands how materials are approved for use, since ultimately it is the practitioner who must assume the direct legal risks of using materials in the patient. In the simplest sense, a biocompatible material or device does not harm the patient. Estrogenicity—The potential of a chemical to act in the body in a manner similar to that of estrogen, the female sex hormone. this effect has been termed microleakage. Even if all 32 teeth were restored on all surfaces with amalgam, the total number of surfaces (counting incisal edges) would be only 160. Biomaterials, safety and biocompatibility. Currently, the Dental Devices Branch of the Center for Devices and Radiological Health regulates premarket clearance of dental devices. Mercury is also ingested as particles produced by wear, and about 45 µg/day of mercury may reach the gut either as the amalgam form or as dissolved and released Hg2+ ions. Most dental practitioners in the United States are keenly aware of the many regulations imposed by the Occupational Health and Safety Administration (OHSA) of the federal government on dental practice. This is considered as a major drawback of clinical studies in this area. Only materials that passed one level were tested further. The Clean Air Act is the law that defines the responsibilities of the U.S. Environmental Protection Agency for protecting and improving air quality and the ozone layer. Mercury occurs in four forms: as the metal (Hg, Absorption of specific metals through the oral mucosa, gastrointestinal tract, or respiratory tract can vary considerably for different chemical forms of a metal. The lowest known level for any observable toxic effect is 3 µg/kg. 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. No effects of mercury have been noted. Modern medical devices and prosthesesare often made of more than one mat… 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. Biocompatibility of dental polymers is an important clinical issue. Since orthodontists treat many children, these types of reports deserve scrutiny. Materials used in dentistry come into direct contact with the hard tissues of the teeth,theoralmucosa,thepulp&theperiapicaltissues. At chronic exposure levels, the symptoms are more subtle and include weakness, fatigue, anorexia, weight loss, insomnia, irritability, shyness, dizziness, and tremors in the extremities or the eyelids. However, in 2005, the ADA decided to phase out the Seal of Acceptance program for professional products. It is an overview of biocompatibility concepts, terminology, outcome data from national registries of adverse effects, and principles of established test methods. It has different technological characteristics, but it does not raise new types of safety and effectiveness questions and is at least as safe and effective as the predicate device. The microscopic gap for the so-called microleakage process may lead to several undesirable events. INTRODUCTION 3 Biocompatibility refers to the study of interaction of various materials with human tissues. Biocompatibility of Dental Biomaterials details and examines the fundamentals of biocompatibililty, also including strategies to combat it. Methyl mercury is a major safety concern because it bioaccumulates through the food chain; its pharmacokinetic half-life is longer (1.5 to 3 months) than that of ethyl mercury (less than 1 week). The incidence of nickel allergy in the general population is somewhere between 10% and 20%, being far more common in females than males. The postoperative discomfort or pain caused by treatment with dental materials may result from any of several factors, including thermal trauma, chemical injury, microleakage, and allergy. Furthermore, there are no perfect tests for the confirmation or validation of diagnoses. There have been reports of a growing incidence of contact sensitivity to a variety of substances, including dental materials, in children. In addition, bilateral lichenoid mucositis lesions which will be discussed later, are shown in Figure 7-11 on the buccal mucosa adjacent to gold alloy crowns. The most common implant materials include (1) CP Ti; (2) titanium-aluminum-vanadium alloy; (3) tantalum; and (4) some types of ceramics. An allergic reaction induces an inflammatory response that cannot easily be distinguished from reactions caused by a nonallergic inflammatory process or by low-grade toxicity. Today, the choice of the test method is based on risk assessment, which is also divided into separate stages of analysis. No-observed-adverse-effect level (NOAEL)—The highest tested dose of a substance that has been reported to have no harmful (adverse) health effects on people or animals (U.S. Agency for Toxic Substances and Disease Registry). Further, the periodontal pocket, or gingival sulcus, may accumulate significant concentrations of leached substances that do not accumulate to these levels in other areas. The amount and nature of substances eluted from the material. The complexities mentioned in the previous paragraphs may leave the practitioner wondering about the relevance of the definition of bio-compatibility to dental practice. Classical progression of biocompatibility tests for evaluating a group of new dental materials. 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. Large blue-colored areas, typically referred to as an amalgam tattoo, which is a benign area of discolored membrane in the mouth. Allergy—(1) A hypersensitivity reaction initiated by specific immunological mechanisms (Johansson et al., 2004); (2) abnormal antigen–antibody reaction to a substance that is harmless to most individuals; (3) antigen-inducing an allergic reaction. Excretion may occur through exhaled vapor or through urine, feces, or skin. Bone, seashells, animal teeth, human teeth, metals, resin materials, inorganic compounds, and other tooth replacement materials have been used for replacement of missing teeth. 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. This act required evidence of drug safety before pharmaceutical products could be distributed to the public. How do national and international governments protect dentists and their patients against the use of unsafe or bioincompatible dental products? In contrast, adhesive-bonded, resin-based cements may require acid etching of dentin to remove the smear layer and to expose the collagen mesh that allows infiltration of the bonding resin. By definition, biocompatibility is the interaction between a patient and a medical treatment, and evaluates the safety of those treatments for specific patients. However, even with the enormous number of peer-reviewed publications that have resulted from investigations of alleged toxic and immunological reactions to mercury in dental amalgam, the evidence, thus far, has been regarded by some groups as inconclusive. Estrogenicity is the ability of chemicals from the environment, called xenoestrogens, to mimic the hormone estrogen in the body of the exposed person. Molecular biology and imaging techniques have recently been introduced. An allergic reaction occurs when the body recognizes a substance, molecule, or ion as foreign, and the human immune system can react quickly, as during an anaphylactic reaction or slowly in delayed contact dermatitis. The interactions that occur will depend upon the material, the host, and what forces and conditions are imposed on the material (its function). These are classified as Type I, II, or III reactions, according to the Gell and Coombs classification of immune responses (Gell and Coombs, 1963; Rajan, 2003). A dental implant that is osseointegrated today may or may not be osseointegrated in the future. 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. The color of the material depends upon the light source, how the light interacts with the material, and the visual response of the observer. Citation: Roua Mohammed Almadani., et al. 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. By the end of 2011, three sessions of the Intergovernmental Negotiating Committee (INC) organized by UNEP had been held to prepare a Global Legally Binding Instrument on Mercury: INC1 (June 7-11, 2010, Stockholm, Sweden), INC2 (January 24-28, 2011, Chiba. Given the importance of biocompatibility issues to dental practitioners, it is surprising how few understand what biocompatibility really is and what its consequences are. Xenoestrogen—A chemical that is not indigenous to the body but which acts in a manner similar to that of estrogen. The specific causes of these effects are difficult to diagnose because of the multifactorial nature of dental treatment and the subjective nature of patients’ complaints or descriptions of their symptoms. If it is not time limited, one can assume that the erythema may have been caused by an allergic reaction. An analysis of a database for 450 subjects with peanut allergy indicated that the ED10 was 12.3 mg of whole peanut (average mass of 1000 mg per whole peanut) compared with a 5% increase (ED05), corresponding to an ingested mass of 5.2 mg (Taylor et al., 2012). Although it is unclear whether leakage toward or into the dental pulp chamber is a major factor in the biological response to dental materials, one must be aware of potential immune responses in the pulp and periapical tissues that may occur independently of leakage phenomena. Elemental mercury is transported to, The most common forms of mercury that occur naturally in the environment are metallic mercury, inorganic salts, mercuric sulfide (HgS), mercuric chloride (HgCl, 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). Several studies have estimated the number of amalgam surfaces needed to expose an individual to mercury concentrations with a minimum observable effect (slightly impaired psychomotor performance, detectable tremor, and impaired nerve conduction velocity). Methyl mercury is not produced from amalgams but is generally a product of bacteria or other biological systems acting on metallic mercury. Biocompatibility testing in the future may lead to more reliable predictions of adverse effects, and this knowledge of biological properties may allow us to formulate materials that provide specific, desired biological responses. Some materials, such as latex, can cause allergy directly by activating antibodies to the material. For air in the workplace, the Occupational Safety and Health Administration has set a permissible exposure limit (PEL) for mercury vapor in air of 0.1 mg/m, Several studies have shown that amalgams release sufficient vapor to cause absorption of between 1 and 3 µg/day of mercury, depending on the number and size of amalgam restorations present (, Concerns about mercury stem from its toxicity and its relatively long half-life in the body. Biocompatibility—(1) General definition: The ability of a biomaterial to perform its desired function with respect to a medical (or dental) therapy, without eliciting any undesirable local or systemic effects in the recipient or beneficiary of that therapy, but generating the most appropriate beneficial cellular or tissue response in that specific situation, and optimizing the clinically relevant performance of that therapy (Williams, 2008); (2) Long-term implantable device: Ability of the device to perform its intended function, with the desired degree of incorporation in the host, without eliciting an undesirable local or systemic effect in that host (Willliams, 2008); (3) Scaffold material for tissue engineering product: Ability to perform as a substrate that will support the appropriate cellular activity, including the facilitation of molecular and mechanical signaling systems, in order to optimize tissue regeneration, without eliciting any undesirable local or systemic responses in the eventual host (Williams, 2008). According to currently accepted guidelines, this means that the interface with bone will be located within approximately 10 nm of the implant, without intervening fibrous tissue. This much smaller gap has been claimed to allow nanoleakage, which probably does not allow bacteria or bacterial products to penetrate the marginal gaps of the restoration and the pulp. Biocompatibility It is the ability of a material to elicit an appropriate biological response in a given application in the body. The MDA of 1976 required that FDA classify all medical devices into one of three classes, according to risk, Class I, Class II, and Class III. In 1930, the American Dental Association (ADA) formed a Council on Dental Therapeutics to oversee the evaluation of dental products. Define biocompatibility. Otherwise known as “natural dentistry” or “holistic dentistry”, is a form of dentistry that relies on a pretty obvious (although often overlooked) premise: the body is an interconnected system. ANSI/ADA Standard No. Most scientists agree today that no material is truly inert in the body. Plaque accumulation also increases on roughened surfaces, and this may contribute to periodontal disease or caries. Testing of dental materials also includes tests for pulp irritation responses, pulp capping effects, endodontic applications, and dental implant performance. A Type II response is a cytotoxic hypersensitivity reaction, Type III is an immune complex hypersensitivity reaction, Type IV is a delayed or cell-mediated hypersensitivity, and Type V is a stimulating-antibody reaction, which is rare and sometimes classified as a subcategory of Type II (, Precursors to Adverse Effects of Dental Materials, Products that pass the primary tests, such as the toxicity test, then progress to secondary and usage tests (. This type is often associated with contact dermatitis. the body burden of mercury have been developed, including those based on the analysis of blood, urine, and hair. 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