The Minamata Convention on Mercury and its implications for management of dental caries in low‐ and middle‐income countries

Abstract

BACKGROUND Dental caries has become a ubiquitous public health problem despite overwhelming evidence that it is preventable1,2. Petersen reported that virtually all populations are affected globally, with 60%–90% of schoolgoing children and most adults affected by this condition 1. Dental caries is a disease of the dental hard tissues characterised primarily by demineralisation following production of acid through the fermentation of carbohydrates by oral bacteria, as described in Keyes’ triad. Left untreated, caries progresses to pulpitis, a painful condition warranting emergency intervention. Conventionally, the treatment modality for caries has been through elimination of affected tooth structure and placement of direct and indirect restorations3. An ideal restorative material should be biocompatible, resistant to fracture, demonstrate longevity, be affordable and easy to manipulate, even in a resourcestrained environment4. In low- and middle-income (LMI) countries, lack of prioritisation of oral health as a result of its often morbid, but not fatal, nature, and in the face of limited resources, typically means minimal investment in the infrastructure necessary for advanced restorative treatment. In such countries, conventional caries treatment is not readily available and the ensuing alternative is extraction to provide immediate relief of symptoms; the partially dentate or completely edentulous state following tooth mortality is associated with reduced quality of life1,2. Dental amalgam is one of the oldest direct dental restorative materials, its use spanning more than a century. Amalgam is an alloy of a powder comprising silver, tin and copper triturated with triple distilled mercury into a soft pliable mass which is condensed into a cavity and carved, prior to setting, to a rigid solid. Dental amalgam has several advantages. It has adequate compressive strength of more than 400 MPa, is inexpensive and is easy to manipulate. It is also radiopaque and exhibits self-sealing ability as a result of corrosion products. However, its disadvantages include its metallic appearance as well as its tendency to corrode in the oral cavity, which renders it unaesthetic. Additionally, dental amalgam is brittle in tension and is not adhesive and therefore requires extensive tooth preparation to ensure mechanical retention and adequate bulk to prevent fracture. Moreover, silver–mercury amalgam is a mercurybased product and is now scheduled to be phased down following the Minamata Convention on Mercury in 2013. The Convention is a global treaty whose agenda seeks to reduce environmental impact from mercury waste through phase-out of mercury-based products and cessation of manufacture of mercury. Although there is no proof of any adverse reactions in humans from dental amalgam, mercury is a well-known toxic substance and precaution is mandatory when handling it in the dental surgery. The looming phase-down of dental amalgam by 2020 presents a challenge to the dental profession5. Apart from its remarkable compressive strength, silver–mercury amalgam is one of the simplest to use and affordable restorative materials, making it readily accessible. The phase-down of dental amalgam is likely to hinder access to affordable restorative dental treatment in LMI countries3. Therefore, there is an urgent need to find an alternative with minimal adverse environmental impact that offers the excellent properties that characterise amalgam4. This commentary addresses the global burden of dental caries and inequalities that exist in LMI countries, such as Kenya. It highlights the challenges of disease management, which are expected to worsen during the imminent phase-down of dental amalgam, and proposes practical and cost-effective solutions. The intent is to increase awareness by urging a paradigm shift that requires curriculum review in dental schools to promote disease prevention and further research on restorative alternatives. The articles included were accessed through a systematic search on PubMed and Google Scholar using the specified keywords. A manual search of gray literature was also performed for additional articles. © 2019 FDI World Dental Federation 1