The Dental Association says it is appalled by the appearance of two anti-fluoride billboards in Hamilton that say informed dentists vote "no" to fluoride.
The city is holding a referendum on whether to resume adding fluoride to its water supply in October.
Hamilton City Council recently decided to drop fluoridation but then agreed to hold a non-binding vote.
Dental Association spokesperson Steven Pawley says the billboards are insulting, false and bordering on defamation.
He says the three dentists used on the billboard are not local and, while they are entitled to their opinions, they represent a very small minority of the profession.
Dr Pawley says the trio do not represent the association's position on fluoride.
