Traditional Dentistry vs Holistic Dentistry: The Great Amalgam Debate

Let’s start with defining traditional dentistry and holistic dentistry. Traditional dentistry is the profession concerned with the prevention and treatment of oral disease, including diseases of the teeth and supporting structures and diseases of the soft tissues of the mouth. Holistic dentistry is the equivalent of complementary and alternative medicine for dentistry. I want to be completely transparent, so I feel it is necessary to disclose the fact that I have never worked in a holistic dental practice. All the information I will be sharing I found through research and not first-hand experience.

Upon researching holistic dentistry to better understand the difference, I found one subject to be the basis of holistic dentistry. That subject was amalgam restorations. I’ll start there and continue through the other differences I have found in future posts.

Amalgam Restorations

Though I’m sure many traditional dentists still use amalgam for certain circumstances, many now exclusively use composite resin material. This is the same material used by holistic dentists. Traditional dentists generally do not recommend the removal of an amalgam restoration, unless there is an issue with the restoration, such as secondary decay (cavity beside or under the current filling), or a fracture in the restoration. Amalgam restorations are very durable and often last for a very long time. Holistic dentists do recommend replacing all amalgam restorations, this is due to the risk of mercury exposure. Holistic dentists do not use amalgam restorative material at all.

Is mercury toxicity a real concern? Are you considering having your amalgam restorations removed for fear of mercury toxicity? Mercury is found in the Earth’s crust, it is found in your everyday environment. People are exposed via air, water and food. This means that even if you do not have amalgam fillings you still have small but measurable levels of mercury in your blood and urine. [1] In a study published in Human and Experimental Toxicology, researchers measured levels of mercury in the brain of 32 cadavers. Of these cadavers 10 had amalgam restorations and 22 were amalgam free. Mercury levels were found in the brain of both groups. Cadavers with amalgam restorations had a minimum of 0.3 ug/g and a maximum of 2.34 ug/g mercury in their brain. Cadavers that were amalgam free had a minimum of 0.17 ug/g and a maximum of 1.76 ug/g mercury in their brain. The study concluded that there is no correlation between the presence of amalgam fillings and mercury levels in the brain. [2] Most mercury exposure related to dental amalgam restorations occur during placement or removal of the restoration. Mercury does not collect irreversibly in human tissues, however not all individuals respond the same to mercury exposure conditions, and significant individual differences have been indicated in mercury accumulation, distribution and elimination. [1,3] The average half-life of mercury is 55 days, meaning mercury you were exposed to years ago may no longer be present in your body. [1]

Many holistic dentists use what is referred to as the safe mercury amalgam removal technique (SMART). This technique has added safety measures for removing amalgam restorations. Traditional dentists use masks, water irrigation and high-volume suction to reduce inhalation of mercury gas. Holistic dentists that use the SMART technique use the same basic procedure with additional precautions such as advanced air filtration, opening of windows, protective gowns for the dentists, assistant and patient, as well as having patients swish and swallow a charcoal slurry before the procedure. The masks used are respiratory grade masks and patients wear a nasal mask for oxygen delivery to reduce inhalation of mercury vapor. [4] This leads to alternatives to the use of amalgam restorations. The most common replacement options are composite resin material or milled ceramic. Many holistic dentists claim to be metal free since they avoid using amalgam restorations, but is that a misnomer? Let’s look at the composition and safety of these two alternatives.

Composite Resin

Traditional dentists offer composite resin restorations as well as holistic dentists. There are many different brands and manufacturers of composite resin filling material. Therefore, composition does vary slightly. The main ingredients found consistently in resin composites are Bis-GMA, Bis-EMA, UDMA, and TEGDMA. [5] What exactly do all those acronyms mean?

Bis-GMA stands for bisphenol A glycidyl methacrylate, it is a monomer used in composite resins, this allows the resin to polymerize for bonding. Bis-GMA is genotoxic for human lymphocytes. It can cause a broad spectrum of DNA damage including severe DNA double strand breaks in human lymphocytes. However, it is important to mention that only at maximum concentrations was a decrease in viable lymphocytes noted. [6] Bisphenol A (BPA) is released from composite resins containing Bis-GMA. This happens through salivary enzymatic hydrolysis, when enzymes facilitate the cleavage of bonds in molecules. This process plays an important role in the digestion of food. BPA is detectable in saliva for up to 3 hours after placement of a composite resin. [7] I could not find any research that was clear on the quantity or duration of systemic BPA absorption after restoration placement.

Bis-EMA stands for ethoxylated bisphenol-A dimethacrylate, and TEGDMA stands for triethylene glycol dimethacrylate these are also both monomers. These monomers have been found to be cytotoxic via apoptosis, induced genotoxic effects, delay the cell cycle, and they influence the cell response of the innate immune system. They have also been found to inhibit odontoblast cell functions (odontoblasts are cells in the pulp of the tooth that produces dentin) or delay the odontogenic differentiation and mineralization processes (this is important for dentin formation and pulp repair) in pulp-derived cells including stem cells. This indicates these monomers can act as environmental stressors which inevitably disturb regulatory cellular networks through interference with signal transduction pathways. [8]

UDMA stands for urethane dimethacrylate, also a monomer. UDMA has been shown to inhibit growth of certain cells, contribute to cell apoptosis and necrosis, and deplete the production of glutathione at certain doses. [9]

In addition to the monomers listed above composite resin material has fillers. These fillers are either made of glass or ceramics. Glass fillers include crystalline silica, silicone dioxide, lithium/barium-aluminum glass, and borosilicate glass containing zinc/strontium/lithium. Ceramic fillers are made of zirconia-silica, or zirconium oxide. There is evidence that composite resins release ions such as fluoride, strontium, and aluminum from these fillers due to degradation and erosion over time. [10,16] This part of the resin composite is what makes me question the “metal free” claim. Here is why, if you don’t remember chemistry class in high school let me remind you that lithium, barium, and aluminum are all metals. Zirconium and zinc are transitional metals. Transitional metals are ductile, malleable and conduct heat and electricity. They can exhibit several oxidation states. Sometimes zinc and mercury are included in the list of transitional metals. [11] Borosilicate glass is composed of silicon, boron (which is on the border between metals and nonmetals), sodium (a silvery-white highly reactive metal), potassium (also a silvery-white metal), and aluminum (obviously a metal). [12] I’ll let you decide for yourself if composite resin material should be considered “metal free”.

Milled Ceramic Restorations

The other option is milled ceramic restorations. This procedure is offered in holistic dental practices as well as traditional dental practices. These restorations are milled from a block of ceramic restoration material often in-office by a computer design or by a dental lab. The composition of the materials falls into 4 categories: glass based, glass based with fillers, crystalline based with glass fillers, and polycrystalline solids. [14]

Glass based ceramic material is made from material that contain mainly silicon dioxide, which contains various amounts of alumina also referred to as aluminum oxide. Aluminum oxide is a chemical compound of aluminum and oxygen. It is produced from bauxite, a sedimentary rock with a relatively high aluminum content. [13,14]

Glass based with fillers, this category has so many different combinations it can be broken down into subcategories. The glass portion is the same as the previous mentioned glass-based material. The difference in the categories is the different type of crystals that have been added or grown in the glassy matrix. The primary crystal types are leucite, lithium disilicate, or fluoroapetite. Leucite is a rock forming mineral composed of potassium and aluminum tectosilicate. Lithium disilicate is composed of lithium dioxide, alumina, potassium oxide, phosphor oxide, quartz and other components. Fluoroapetite is a phosphate mineral with a chemical composition that includes calcium, phosphate and fluorine. Fluorine is one of the ingredients in many fluoride varnishes and gels. Most holistic dental practices do not recommend the use of fluoride. If you are going to a holistic dentist with hopes of avoiding fluoride, you might want to inquire about the restorative products they use, many contain fluoride or fluorine. [14]

Crystalline based with glass fillers is made primarily from alumina, alumina/zirconium, or alumina/magnesia mixture. As mentioned before alumina is a chemical compound of aluminum and oxygen. Zirconium is a transitional metal, and magnesia or magnesium oxide is an alkali earth metal. [13,14,15]

Polycrystalline solids are composed of either aluminum oxide or zirconium oxide. The same materials mentioned above. This ceramic is formed by directly sintering crystals together without a matrix. [14,15]

The cytotoxicity of dental ceramics has been studied. Most dental ceramics caused only mild suppression of cell function in vitro. The only exception in this study was lithium disilicate which showed cytotoxicity that would not be deemed acceptable in comparison to the standards set for amalgam and composite restorations. [17] The good news for patients of holistic dentists is that most holistic dentists use zirconium and not lithium disilicate.

Zirconium is a fantastic material to use for dental restorations, many traditional dentists widely use it as well. If you are seeking treatment with a holistic dentist, it is because you prefer a more natural approach to dental care. The bad news about zirconium for holistic dentists is that unpurified zirconia contains non negligible levels of uranium and thorium, both highly radioactive. So, the question remains, how much natural radioactivity is found in dental grade zirconium? Though there was radioactivity detected from zirconium ceramics, the levels were negligible. It was considered lower than many hazardous radioactive appliances in our environment. [18]

Conclusion

I did not write this to scare people or to deter them from seeking dental treatment. Quite the opposite, I wrote this to educate people on the safety of dental materials. Though all these materials contain potentially harmful substances, they all fall within safety standards. Every single one of them have been found to be equally safe. If you have an amalgam filling, don’t fret about it. If you want to have your amalgam fillings replaced, go for it. It really does not matter, just make sure you take care of your teeth. Oral health is very important for overall health. If you neglect your oral health, you will pay for it with other systemic health issues. There are so many systemic diseases directly related to oral health. Educate yourself and understand the risks versus benefits of dental treatment. Most importantly, if you have concerns discuss them with your dentist or hygienist. They may be able to help you understand treatment options and materials used for restorations.

*American Dental Association’s statement on amalgam restorations: “Dental amalgam is considered a safe, affordable and durable material that has been used to restore the teeth of more than 100 million Americans. It contains a mixture of metals such as silver, copper and tin, in addition to mercury, which binds these components into a hard, stable and safe substance. Dental amalgam has been studied and reviewed extensively and has established a record of safety and effectiveness.”

*American Dental Association’s statement on composite resin restorations: “The ADA is a professional association of dentists committed to the public’s oral health. As such, the ADA supports ongoing research on the safety of existing dental materials and in the development of new materials. Based on current research, the Association agrees with the authoritative government agencies that the low-level of BPA exposure that may result from dental sealants and composites poses no known health threat.”

Resources

1. Monika Rathore, Archana Singh, and Vandana A Pant. The Dental Amalgam Toxicity Fear: A Myth or Actuality. Toxicol Int. 2012 May-Aug; 19(2): 81-88. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388771/

2. Ertas E, Aksoy A, Turla A, Karaarslan ES, Karaarslan B, Aydin A, Eken A. Human Brain Mercury Levels Related to Exposure to Amalgam Fillings. Hum Exp Toxicol. 2014 Aug; 33(8): 873-7. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24178888

3. Virginia Andreoli and Francesca Sprovieri. Genetic Aspects of Susceptibility to Mercury Toxicity: An Overview. Int J Environ Res Public Health. 2017 Jan; 14(1): 93. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5295343/

4. International Academy of Oral Medicine and Toxicology. The Safe Mercury Amalgam Removal Technique (SMART). Retrieved from https://iaomt.org/resources/safe-removal-amalgam-fillings/

5. Laiza Tatiana Poskus, Mauricio Chagas, Antonio Marcelo Accetta Latempa, Eduardo Moreira da Silva. Influence of Post-cure Treatments on Hardness and Marginal Adaptation of Composite Resin Inlay Restorations: An In Vitro Study. J Appl Oral Sci. 2009 Nov; 17(6): 617-22. Retrieved from https://www.researchgate.net/publication/40757939_Influence_of_post-cure_treatments_on_hardness_and_marginal_adaptation_of_composite_resin_inlay_restorations_An_in_Vitro_study

6. Kinga Drozdz, Daniel Wysokinski, Renata Krupa, and Katarzyne Wozniak. Bisphenol A-glycidyl methacrylate induces a broad spectrum of DNA damage in human lymphocytes. Arch Toxicol. 2011 Nov; 85(11): 1453-1461. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3204149/

7. Abby F. Fleisch, MD, Perry E. Sheffield, MD, Courtney Chinn, DDS, MPH, Burton L. Edelstein, DDS, MPH, and Phillip J. Landrigan, MD, MSc. Bispenol A and Related Compounds in Dental Materials. Journal of the American Academy of Pediatrics. Retrieved from https://pediatrics.aappublications.org/content/pediatrics/126/4/760.full.pdf?ck=nck

8. Krifka S, Spagnuolo G, Schmalz G, SChweikl H. A Review of Adaptive Mechanisms in Cell Response Towards Oxidative Stress Caused by Dental Resin Monomers, Biomaterials. 2013 Jun; 34(19): 4555-63. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/23541107

9. Chang HH, Chang MC, Lin LD, Lee JJ, Wang TM, Huang CH, Yang TT, Lin HJ, Jeng JH. Then Mechanism of Cytotoxicity of Urethane Dimethacrylate to Chinese Hamster Ovary Cells. Biomaterials. 2010 Sep; 31(27): 6917-25. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/20579731

10. J., Bonsor, Stephen (2013). A clinical guide to applied dental materials. Pearson, Gavin J. Amsterdam: Elsevier/Churchill Livingstone. pp. 73–75

11. Periodic Table: Transitional Metals. Retrieved from http://www.chemicalelements.com/groups/transition.html

12. M. Hasanuzzaman, A. Rafferty, M. Sajjia, A.G. Olabi. Properties of Glass Materials. Reference Module in Materials Science and Materials Engineering, 2016 edition. Retrieved from https://www.sciencedirect.com/topics/chemistry/borosilicate-glass

13. Alumina Refining. Retrieved from https://www.aluminum.org/industries/production/alumina-refining

14. Arvind Shenoy, and Nina Shenoy. Dental Ceramics: An Update. J Conserv Dent. 2010 Oct-Dec; 13(4): 195-203. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3010023/

15. Edward A. McLaren, DDS, MDC; Phong Tran Cao, DDS. Ceramics in Dentistry – Part I: Classes of Materials. Inside Dentistry Oct 2009; 5(9). Retrieved from https://www.aegisdentalnetwork.com/id/2009/10/many-different-types-of-ceramic-systems-have-been-introduced-in-recent-years-for-all-types-of-indirect-restorations

16. Saurabh K. Gupta, Payal Saxena, Vandana A. Pant, and Aditya B. Pant. Release and Toxicity of Dental Resin Composite. Toxicol Int. 2012 Sep-Dec; 19(3): 225-234. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3532765/

17. Messer RL, Lockwood PE, Wataha JC, Lewis JB, Norris S, Bouillaguet S. In Vitro Cytotoxicity of Traditional Versus Contemporary Dental Ceramics. J Prosthet Dent. 2003 Nov; 39(5): 452-8. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/14586309

18. Bavbek AB, Ozcan M, Eskitascioglu G. Radioactive Potential of Zirconium-dioxide used for Dental Applications. J Appl Biomater Funct Mater. 2014 Jun 12; 12(1): 35-40. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22865573

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