Academy of Clinical Toxicology still claim that mercury from amalgams does not cause illness because "the amount of mercury that they release is not enough to cause a health problem". In response to some people wanting their existing amalgam removed for fear of mercury poisoning, these societies advise that the removal of fillings is likely to cause a greater exposure to mercury than leaving the fillings in place. These societies also claim that removal of amalgam fillings, in addition to being unnecessary health care and likely to cause more mercury exposure than leaving them in place, is also expensive. Dentists who advocate removal of amalgam fillings often recommend wearing breathing apparatus, using high-volume aspiration, and performing the procedure as quickly as possible. Sources of mercury from the diet, and the potential harm of the composite resins to replace the purportedly harmful amalgam fillings, may also need to be considered. Alternative materials Alternative materials which may be suitable in some situations include composite resins, glass ionomer cements, porcelain and gold alloys. Most of these materials, with the notable exception of gold, have not been used as long as amalgam, and some are known to contain other potentially hazardous compounds. Teaching of amalgam techniques to dental students is declining in some schools in favor of composite resin, and at least one school, University of Nijmegen in the Netherlands, eliminated dental amalgam from the curriculum entirely in 2001. This is largely a response to consumer pressure for white fillings for cosmetic reasons, and also because of the increasing longevity of modern resin composites. These alternative dental restorative materials are not free of potential health risks, such as allergenicity, inhalation of resin dust, cytotoxicity, and retinal damage from blue curing light. Chelation therapy Anti-amalgam sources typically promote removal of amalgam fillings and substitution with other materials. Detoxification may also be advised, including fasting, restricted dieting to avoid mercury containing foods, and quasi-chelation therapies, allegedly to remove accumulated mercury from the body. The American College of Medical Toxicology and the American Academy of Clinical Toxicology recommend against chelation therapy and say that chelation therapy can artificially and temporarily elevate the levels of heavy metals in the urine (a practice referred to as "provoked" urine testing). They also mention that the chelating drugs may have significant side effects, including dehydration, hypocalcemia, kidney injury, liver enzyme elevations, hypotension, allergic reactions, and mineral deficiencies. Epidemiology Better dental health