Alzheimer’s disease is the most common form of dementia. It is an irreversible, progressive condition that affects memory, cognitive abilities, and behavior. Patients with Alzheimer’s disease gradually lose their ability to function in day-to-day life without care and assistance. Numbers show that 5.7 million Americans are living with Alzheimer’s and the number of patients is projected to rise to 14 million by 2050[i]. The exact cause of the disease is not known, but many factors play a role. Amalgam has been associated with increased risk of Alzheimer’s, but is that really true?
[i] 2018 Alzheimer’s disease facts and figures, Alzheimer’s Association https://www.alz.org/facts/overview.asp
What is amalgam?
Amalgam is defined as a dental filling material that dentists use to fill cavities that are caused by tooth decay. Dental amalgam has been used to fill cavities in hundreds of millions of patients across the globe for more than 150 years. In a nutshell, amalgam is a combination of metals consisting of mercury and a powdered alloy made out of copper, tin, and silver.
Due to their silver-like appearance, dental amalgam is also referred to as a silver filling. Despite strength and durability of these fillings, amalgam also carries many risks. For instance, it releases a low concentration of mercury through the vapor. Your lungs inhale and absorb that vapor together with mercury. It’s also important to mention that elevated level of mercury can damage kidneys and brain[i].
[i] About dental amalgam fillings, FDA https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/DentalAmalgam/ucm171094.htm
Can amalgam increase Alzheimer’s risk?
Speculations about the potential influence of amalgam on the risk of Alzheimer’s disease have been circulating around for many years. Numerous studies have been carried out on this subject, but they yielded conflicting results.
One study evaluated the relationship between dental amalgam fillings and Alzheimer’s disease in the Taiwanese population. For the purpose of the research, scientists analyzed data from the Longitudinal Health Insurance Database (LHID) which enrolled 1,943,702 people. After exclusion of death cases and persons younger than 65, the total of participants in this study was 207,587. Results, published in the November 2015 issue of the Alzheimer’s Research and Therapy, found that individuals who were exposed to amalgam fillings were at a higher risk of developing this neurodegenerative disease[i].
In addition, some studies have also shown that dental amalgam has adverse effects on neurodevelopment, immune system, oral cavity, gastrointestinal tract, and cardiovascular system. There are indications that mercury from amalgam can cross the blood-brain barrier. The risk of systemic diseases reportedly heightens in individuals with a large number of dental amalgam fillings and those who have had these fillings for long-term[ii].
Not all is bad; many studies confirm the risk of Alzheimer’s is nonexistent in persons with amalgam fillers. Back in 1999, the Lancet published a study which revealed that there is no link between the number, size, location, or time in the mouth of dental amalgams and Alzheimer’s disease. While these fillings do release mercury through vapor, it doesn’t reach the brain. Instead, most of it is excreted or blown out of the mouth[iii]. In addition, some evidence reveals that brain mercury levels aren’t associated with dental amalgam, and it doesn’t appear to be a neurotoxic factor in the pathogenesis of Alzheimer’s disease[iv].
[i] Sun Y-H, Nfor ON, Huang J-Y, Liaw Y-P. Association between dental amalgam fillings and Alzheimer’s disease: a population-based cross-sectional study in Taiwan. Alzheimer’s Research & Therapy. 2015;7:65. doi:10.1186/s13195-015-0150-1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642684/
[ii] Manchanda AS, Narang RS, Kaur N, et al. A systemic review and meta-analysis on the association between amalgam fillings and systemic diseases. Indian Journal of Comprehensive Dental Care 2017 Jan-Jun;7(1):944-51 http://web.b.ebscohost.com/abstract?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=22316973&AN=125527822&h=9prHwjciK82SkKq1nHmq%2fUqtgflBKEb2aUG0llo6EUjOPt%2fcshk3BZ1BanCuO%2fOGa8oDY5KrUuAASaShZ7e7Xw%3d%3d&crl=c&resultNs=AdminWebAuth&resultLocal=ErrCrlNotAuth&crlhashurl=login.aspx%3fdirect%3dtrue%26profile%3dehost%26scope%3dsite%26authtype%3dcrawler%26jrnl%3d22316973%26AN%3d125527822
[iii] Larkin M. Link between dental amalgam and Alzheimer’s disease refuted. The Lancet 1999 Feb;353(9153):649. Doi: 10.1016/S0140-6736(05)75442-8 http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)75442-8/abstract
[iv] Saxe SR, Wekstein MW, Kryscio RJ, et al. Alzheimer’s disease, dental amalgam and mercury. Journal of the American Dental Association 1999 Feb;130(2):191-99. Doi: 10.14219/jada.archive.1999.0168 https://www.sciencedirect.com/science/article/pii/S0002817714657135
What others say
The Alzheimer’s Association discussed the relationship between amalgam and Alzheimer’s on their post about myths associated with this disease. They explained that there is no relationship between silver fillings and Alzheimer’s[i].
According to the International Journal of Dentistry current evidence doesn’t justify discontinuing the use of amalgam and mercury released from these feelings doesn’t contribute to systemic disease[ii].
Mayo Clinic explains that amalgam fillings are safe and the growing body of evidence finds them to be effective, safe, and long-lasting treatment for tooth decay[iii].
[i] Alzheimer’s myths, Alzheimer’s Association https://www.alz.org/alzheimers_disease_myths_about_alzheimers.asp
[ii] Uçar Y, Brantley WA. Biocompatibility of Dental Amalgams. International Journal of Dentistry. 2011;2011:981595. doi:10.1155/2011/981595. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227436/
[iii] Amalgam is a reliable and durable choice for fillings, Mayo Clinic https://newsnetwork.mayoclinic.org/discussion/amalgam-is-a-safe-and-durable-choice-for-fillings/
Conclusion
The association between amalgam fillings and Alzheimer’s is a subject of many debates and studies that, at this point, have no consensus. Studies yield different results, and it is safe to say we’re going to witness many more of them in the future. It would be impossible to answer whether amalgam contributes to Alzheimer’s risk or not due to conflicting evidence. If you have any concerns about this subject or your filling, then it would be useful to consult your dentist.
References
[1] 2018 Alzheimer’s disease facts and figures, Alzheimer’s Association https://www.alz.org/facts/overview.asp
[1] About dental amalgam fillings, FDA https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/DentalAmalgam/ucm171094.htm
[1] Sun Y-H, Nfor ON, Huang J-Y, Liaw Y-P. Association between dental amalgam fillings and Alzheimer’s disease: a population-based cross-sectional study in Taiwan. Alzheimer’s Research & Therapy. 2015;7:65. doi:10.1186/s13195-015-0150-1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642684/
[1] Manchanda AS, Narang RS, Kaur N, et al. A systemic review and meta-analysis on the association between amalgam fillings and systemic diseases. Indian Journal of Comprehensive Dental Care 2017 Jan-Jun;7(1):944-51 http://web.b.ebscohost.com/abstract?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=22316973&AN=125527822&h=9prHwjciK82SkKq1nHmq%2fUqtgflBKEb2aUG0llo6EUjOPt%2fcshk3BZ1BanCuO%2fOGa8oDY5KrUuAASaShZ7e7Xw%3d%3d&crl=c&resultNs=AdminWebAuth&resultLocal=ErrCrlNotAuth&crlhashurl=login.aspx%3fdirect%3dtrue%26profile%3dehost%26scope%3dsite%26authtype%3dcrawler%26jrnl%3d22316973%26AN%3d125527822
[1] Larkin M. Link between dental amalgam and Alzheimer’s disease refuted. The Lancet 1999 Feb;353(9153):649. Doi: 10.1016/S0140-6736(05)75442-8 http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)75442-8/abstract
[1] Saxe SR, Wekstein MW, Kryscio RJ, et al. Alzheimer’s disease, dental amalgam and mercury. Journal of the American Dental Association 1999 Feb;130(2):191-99. Doi: 10.14219/jada.archive.1999.0168 https://www.sciencedirect.com/science/article/pii/S0002817714657135
[1] Alzheimer’s myths, Alzheimer’s Association https://www.alz.org/alzheimers_disease_myths_about_alzheimers.asp
[1] Uçar Y, Brantley WA. Biocompatibility of Dental Amalgams. International Journal of Dentistry. 2011;2011:981595. doi:10.1155/2011/981595. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227436/
[1] Amalgam is a reliable and durable choice for fillings, Mayo Clinic https://newsnetwork.mayoclinic.org/discussion/amalgam-is-a-safe-and-durable-choice-for-fillings/