Dental Amalgam Position Statement

The South African Dental Association supports the position  of the World Dental Federation (FDI), American Dental Association (ADA) and National Health Institute  with the gradual phasing down of dental amalgam as opposed to the complete phasing out of amalgam use altogether.

SADA is in agreement with the FDI context that the ‘’phase down and potential phase out of dental amalgam is not a one-size-fits-all solution for all countries and tailored strategies should be implemented at the country level based on specific needs and situations.’’ Furthermore, we share the position of the WHO that efforts should focus on accelerating the phase down of dental amalgam through a comprehensive, stepwise, and inclusive process that considers a timescale for implementation according to national contexts.¹⁵

Mercury exposure from amalgam restorations
Amalgam has been in use in dentistry for about 150 years and is often the restoration material of choice, especially in third world countries, due to its low cost, ease of application, strength, durability and bacteriostatic effect.¹

If placed under ideal conditions, it is longer lasting and the least technique sensitive of all restorative materials. Most standard dental amalgam formulations contain approximately 50% elemental mercury.

Experimental evidence consistently demonstrates that mercury that is released from dental amalgam restorations is absorbed by the human body, particularly during the placement or removal of dental restorations.

The exposure to mercury from restorations depends on the number and size of restoration, composition, chewing habits, food texture, grinding, brushing of teeth, and many other physiological factors. However, it is maintained that the levels of mercury absorbed by the body due to the release of mercury vapor from amalgam restorations, while detectable, do not approach those recognized to cause illness.²

It has therefore been confirmed that amalgam restorations can be used safely in most patients, with some notable caveats, and studies have uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.³

Hypersensitivity reactions by amalgam restorations
The constant exposure to mercury in amalgam restorations may sensitize some individuals, making them more susceptible to oral lichenoid lesions. There is evidence that a certain percentage of these lichenoid lesions are caused by amalgam restorations,⁴ but other restorative materials can also cause lichenoid lesions. It was also noted that the restorations associated with lichenoid lesions are poorly contoured, corroded and old. Hence corrosion of amalgam restoration or perhaps the biofilm present on such restorations may contribute to the development of hypersensitive reaction rather than material itself.⁵

Symptoms of an amalgam allergy include skin rashes in the oral, head and neck area, itching, swollen lips, localized eczema-like lesions in the oral cavity. These clinical signs usually require no treatment and will disappear on their own within a few days of exposure. However, in some instances, an amalgam restoration will have to be removed and replaced with alternate restorative material.

Where this has been conclusively identified by the necessary allergy tests, existing amalgam fillings can be removed by any dentist using a rubber dam, a device that prevents particles from entering the oral cavity, and high-speed suction to ensure that the amalgam is evacuated immediately it is removed.

Mercury management in the dental surgery
According to the ADA, dental best management practices for amalgam waste handling and disposal⁶ include:

Following the best management practices as outlined above, practitioners may effectively manage amalgam as a waste product without it becoming harmful.

Affordability
Dental amalgam is without doubt the restorative material that enables the maximum number of people to afford dental restorative care. Even in the private practice setting, medical aid benefits for amalgam restorations are roughly 20% more cost effective than composite for a three-surface posterior amalgam restoration.¹⁴ While the purchase and installation of the equipment involved in safe amalgam disposal may incur an additional cost, the discussion paper indicates that these costs may not be excessive and may be offset by subsidies.

Amalgam substitutes
In the recent years’ composites, glass ionomer cements and a variety of hybrid structures have been used due to increased demand for aesthetic restorations. In comparison to amalgam, composite resins exhibit high strength and require minimal tooth preparations due to its adhesive properties.

However, disadvantages include technique sensitivity, polymerization shrinkage leading to post-operative sensitivity, micro leakage, less clinical durability when compared to amalgam restoration and expensive availability.^{7, 8, 9}

Studies by Demarco et al have shown that the survival rate of amalgam restorations was 94.4% and that of composite restoration was 85.5%, concluding that amalgam restorations lasted 20% more than similar composite restorations.¹⁰ Similar findings were reported in a 7 year follow up by Bernardo et al stating that the longevity of amalgam restorations was 94.4% and that of composites was at 85.5%, concluding that the mean annual failure rates of composite restorations was almost three times greater than those of amalgam restorations.¹¹

Furthermore, there is a general belief that amalgam restorations show a higher rate of cusp fracture than composite restorations but studies by Michael et al found that there is no significant difference in the cusp fracture ratio. Most studies have shown that composite restorations are not as durable as amalgam restorations.¹²

At a five-year recall period in children, it has been observed that composite restorations have to be replaced or repaired at higher rates than amalgam restorations.¹³ Ceramic and gold restorations may also have their place as amalgam alternatives, particularly when the restoration needed is large, but both of these treatment modalities are considerably more expensive than a similarly sized amalgam.

Thus, it stands to reason that while composites provide an aesthetic alternative, at present there is no material that matches or is superior to amalgam especially in the restoration of large posterior cavities.

The phasing down of dental amalgam before the availability of safe, effective, and affordable alternatives, particularly in resource-limited settings, would negatively impact oral health from both an individual and population perspective. It could lead to quality dental treatments being compromised, an increase in the number of teeth extractions as access to appropriate treatment regimens are no longer available, specifically in low- and middle-income countries.

SADA supports the development of a quality mercury-free restorative material that is affordable, biocompatible, clinically effective, user-friendly, and environmentally sound but in the interim, we are of the opinion that amalgam remains a viable and effective restoration material.

Current South African Private Practice
A review of the statistics provided by one managed care organisation with regard to the billing patterns of practitioners in the private sector placing restorations has revealed that the phase-down of amalgam is already underway:

From the above data, the following is evident:

1. There is a significantly higher number of resin restorations being placed as compared to Amalgam in both 2019 and 2020, irrespective of the size of the restoration. Amalgam only accounts for 8.36% of the total restorations billed in 2020, while the remaining 91.64% were resin.
2. The number of amalgam restorations placed in 2020 is lower than in 2019.

This is indicative of a gradual phase down of amalgam already in place in the private practice setting. Whether the same is true for state run facilities is unknown. Unfortunately, data of amalgam use in the public sector is not available.

Conclusion
While SADA supports the continued phase down of dental amalgam, we believe that dentists must be given access to alternatives that are safe, effective and affordable before there is a complete phase out. We believe that a greater emphasis must be placed on prevention, increased research on amalgam alternatives, and best management practices for amalgam waste.

References

1. Amalgam at the new millennium. Berry TG, Summitt JB, Chung AK, Osborne JW J Am Dent Assoc. 1998 Nov; 129(11):1547-56.
2. Roberson TM, Heymann HO, Swift EJ. Sturdevant's Art and Science of Operative Dentistry. 5th ed. Missouri: Mosby Inc; 2006. pp. 151–64.
3. Brownawell AM, Berent S, Brent RL, Bruckner JV, Doull J, Gershwin EM, Hood RD, Matanoski GM, Rubin R, Weiss B, Karol MH. The potential adverse health effects of dental amalgam. Toxicol Rev. 2005;24(1):1-10. doi: 10.2165/00139709-200524010-00001. PMID: 16042501.
4. Resolution of lichen planus following removal of amalgam restorations in patients with proven allergy to mercury salts: a pilot study. Smart ER, Macleod RI, Lawrence CM Br Dent J. 1995 Feb 11; 178(3):108-12.
5. Local adverse effects of amalgam restorations. McCullough MJ, Tyas MJ Int Dent J. 2008 Feb; 58(1):3-9.
6. American Dental Association. Best management practices for amalgam waste. October 2007. Accessed July 15, 2020.
7. Dunne SM, Gainsford ID, Wilson NH. Current materials and techniques for direct restorations in posterior teeth. Part 1: Silver amalgam. Int Dent J. 1997;47(3):123-36.
8. Roeters JJ, Shortall AC, Opdam NJ. Can a single composite restoration serve all purposes? Br Dent J 2005;199(2):73-79
9. Boharty BS, YeQ, Misra A, Sene F, Spencer P, Posterior composite restoration update, focus on factors influencing form and function. Clinical Cosmel Investing Dent;2013; 5:33-42.
10. Soncini JA, Maserijian NN, Trachtenberg F, Tavares M, Hayes C. The longevity of amalgam versus compomer/composite restorations in posterior primary and permanent teeth. J Am Dent Assoc.2007; 138:763-72.
11. Bernardo M, Luis H, Martin MD, Leroux BG, Rue T, Leitao J, et al. Survival and reasons for failure of amalgam versus composite posterior restorations placed in a randomized clinical trial. J Am Dent Assoc.2007; 138:775-83.
12. Mackert JR Jr, Wahl MJ. Are there acceptable alternatives to amalgam? J Calif Dent Assoc. 2004 ;32(7):601-10.
13. Kyou-Li Kim, Cheol Namgung and Byeong-Hoon Cho. The effect of clinical performance on the survival estimates of direct restorations. Restor Dent Endod. 2013;38(1):11-20.
14. Discovery Health 2021 benefit schedule.
15. World Health Organization. Strategic planning for implementation of the health-related articles of the Minamata Convention on Mercury. Geneva: World Health Organization; 2019