The water in Hastings remains fluoride-free, and it is causing major concern among oral hygiene staff at Hawke's Bay District Health Board.
Fluoride was supposed to be added back to the water last year but Hastings District Council group manager asset management Craig Thew said "the dosing system at the treatment plants was being used for chlorine rather than fluoride".
He said fluoride will be added when all the treatment plant upgrades are in place and operational mid-2021.
He added that no measures were being taken in the interim to re-introduce fluoride.
Hastings was the first place in New Zealand to have fluoride added to its urban water as a means of preventing tooth decay, in 1954, but the water supply has been fluoride-free since the Havelock North gastro-outbreak in 2016.