Dental Tribune Asia Pacific

Study finds the use of amalgam in NZ is rapidly decreasing

By Dental Tribune International
February 24, 2020

DUNEDIN, New Zealand: A new study by researchers at the University of Otago Faculty of Dentistry in Dunedin has shown that the use of mercury in dental practices around New Zealand has dramatically declined. The study was conducted to help inform teaching and curriculum changes at the university’s faculty of dentistry and provides a better understanding of the phasing down of the heavy metal’s wider use.

In the study, researchers used the faculty’s data on the characteristics of restorations, including information on the material used and the number of surfaces involved for each restoration. Additionally, data from respondents to a national survey of New Zealand dental practitioners on their use of amalgam was used. According to the study results, the use of amalgam decreased from 52.3% of fillings in 1998 to 7.1% in 2017. The study also showed that, of those included in the national survey, 64% considered composite resin to be their preferred filling material, while only 13% favoured amalgam.

Speaking to Dental Tribune International, lead author Dr Jonathan Broadbent said that the study has helped to provide facts for use in implementing changes to the dental curriculum. He explained: “It was more about removing things from the curriculum, like de-emphasising teaching about placing very small amalgam fillings. Now when the junior dental students place amalgam fillings in simulation, instead of teaching them how to polish them to an ultra-high lustre, we teach them how to drill them out and replace them with composite.”

The phasing down of amalgam in private practices is mirrored in the classroom; however, Broadbent noted that they would “keep teaching about amalgam in lectures for a long time to come, even after it stops being taught clinically. Amalgam lasts a long time”. As for the 13% of dentists in New Zealand still preferring to use amalgam, Broadbent said that he himself had experienced the transition to a non-amalgam practice in a private setting and said one has to adapt to a new way of dentistry. “The world of dentistry will not collapse once amalgam is gone,” he added.

In 2019, at the third meeting of the Conference of the Parties to the Minamata Convention on Mercury, the parties renewed their commitment to the phasing out of the use of products which contain mercury. In a press release, it was stated that, by 2020, the manufacture, import and export of batteries, switches, fluorescent lamps, cosmetics, pesticides, barometers and thermometers that do not meet agreed criteria would no longer be legal. These global measures are already being put in place, and Broadbent believes that, if the current rate of decline continues, the university’s faculty of dentistry could become amalgam-free within two years.

New Zealand has signed but not yet ratified the Minamata Convention. Once this happens, a slow phasing out will begin to take place across the country. “Even when the Minamata Convention is ratified by New Zealand, they [dentists] won’t have to stop—rather just use it less and less over time,” said Broadbent.

The study, titled “The dental amalgam phasedown in New Zealand: A 20-year trend”, was published on 29 January 2020 in Operative Dentistry, ahead of inclusion in an issue.

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