discussed relative to its role in the hypersensitivity reactions experienced by dental patients. Chronic exposure to metal corrosion in the oral environment has been associated with oral manifestations such as bone resorption, oral lesions, oral edema and oral cancer and extra-oral issues such as fatigue, hair loss and eczematous rashes in individuals who are hypersensitive to metals (Vrbova, et al., 2021; Sukumatan, et al., 2020). For these reasons, it is imperative that dental professionals understand the different types of metals used in biomaterials, factors that increase corrosion susceptibility of dental restorations, and corrosion’s potential to increase patient hypersensitivity to metals. Doing so will help dental professionals make better- informed decisions about which biomaterials are the safest and most effective.
Crowns, bridges, removable partial dentures, and implants are fabricated from metals such as noble and seminoble alloys, base metal alloys, and titanium-based alloys. Adverse reactions in hypersensitive patients are possible with all metals. Some effects that have been reported include intraoral redness, swelling and pain of the oral mucosa and lips, oral/gingival lichenoid reactions, stomatitis, cheilitis, extraoral urticarial or eczematous lesions, and combinations of two or more of these conditions. Increasing numbers of patients complain of intraoral and extraoral lesions, metallic taste, and skin reactions, which may be related to the dental materials used for restorations. This basic- level course reviews the importance of metals for human health, identifies common harmful metals and their role in disease, and discusses hypersensitivity reactions, with particular regard to metal allergies in medical and dental patients. Corrosion is also
THE ROLE OF METALS IN HEALTH
bone growth, and zinc is important in wound healing and cellular metabolism (NIH, 2016; Harvard Health Publishing , 2021). Sometimes metallic elements work in tandem. For example, copper works with iron to help the body form red blood cells (National Library of Medicine, 2015b). The dietary sources of metals and the roles they play in health are summarized in Table 1.
Metals, such as iron, zinc, copper, manganese, chromium, selenium, and boron, occur widely in nature and are essential for human health (Harvard Health Publishing, 2021; National Institutes of Health [NIH], 2016; Marieb and Hoehn, 2018). Only trace amounts of these metallic elements are needed to support a variety of enzymatic, metabolic, and biochemical functions (Harvard Health Publishing, 2021; Marieb and Hoehn, 2018). For example, small amounts of iron support hemoglobin and
Table 1: Dietary Sources of Metals and Their Role in Human Health Metal Summary of Dietary Source (listed alphabetically)
Role in Health
Iron
Beans, chickpeas, dark chocolate, eggs, green leafy vegetables, iron-enriched bread and cereal, lean meat, liver, nuts, poultry, seafood, tofu. Crab, dairy products, fish, legumes, oysters, pork, poultry, red meats, whole grain products.
Is an essential component of hemoglobin; supports metabolism and bone growth; is necessary for growth, development, normal cellular function. Is important to numerous aspects of cellular metabolism, immune function, wound healing, and growth and development during pregnancy, childhood, and adolescence. Works with iron to aid in bone, hemoglobin, and red blood cell production; is important in healing and energy production; aids in iron absorption. Is needed for protein and fat metabolism, healthy immune system, nerve cells, and regulation of blood sugar; is required for normal bone growth, reproduction, and energy production. Is involved in glucose metabolism and cholesterol and protein synthesis. Is needed for nitrogen metabolism and the conversion of purines to uric acid. Plays critical roles in reproduction, thyroid hormone metabolism, DNA synthesis; is a vital antioxidant that protects the immune system by preventing the formation of free radicals; is necessary for pancreatic function and tissue elasticity. Is needed for calcium uptake to build strong bones; aids in building muscles and increasing testosterone levels; improves thinking skills and muscle coordination.
Zinc
Copper
Beans, cocoa, dried fruits, green leafy vegetables, nuts, organ meats, oysters and other shellfish, potatoes, whole grains.
Manganese Green leafy vegetables, legumes, nuts, seeds, tea, whole grains.
Chromium Basil, beef, brewer’s yeast, broccoli, grape juice, green beans, orange juice, potatoes, red wine, whole grain products. Molybdenum Beans, cereal grains, dark green leafy vegetables, legumes, peas. Selenium Beans, Brazil nuts, brown rice, chicken, dairy products, eggs, garlic, liver, muscle meats, organ meats, salmon, sardines, tuna, vegetables, whole grains.
Boron
Fruits, grains, leafy vegetables, nuts.
Note. Adapted from National Institutes of Health. (2016). Dietary supplement fact sheets. Retrieved from https://ods.od.nih.gov/factsheets/list-all/; National Library of Medicine. (2015a). Boron. Retrieved from https://www.nlm.nih.gov/medlineplus/druginfo/natural/894.html; National Library of Medicine. (2015b). Copper in diet. Retrieved from https://www.nlm.nih.gov/medlineplus/ency/article/002419.htm; and National Library of Medicine. (2015c). Manganese. Retrieved from https://www.nlm.nih.gov/medlineplus/druginfo/natural/182.html.
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