An anti-fluoride group is claiming that fluoride "reduces children's IQ" on posters that are dotted around Dunedin.
The Fluoride Free NZ posters are advertising an event due to be held at the Otago University campus on Tuesday, featuring three international anti-fluoride campaigners.
Former University of Ulster academic Dr Vyvyan Howard, Irish scientist Declan Waugh, and US anti-fluoride campaigner Prof Paul Connett are all speaking at the event.
The university says the group is free to share its views.
"The group is entitled to share its views. There is substantial scientific research on the efficacy of fluoride and it is up to individuals to reach their own conclusions about claims made," an Otago University spokeswoman said.
A 2014 report commissioned by the Prime Minister's Chief Science Advisor Sir Peter Gluckman and the Royal Society of New Zealand found fluoridation of water at the established levels in New Zealand had broad benefits for dental health.
It concluded there were no adverse effects on health as a result of fluoridating public water supplies.
Earlier this year Government MPs were condemned by the opposition for agreeing to host Fluoride Free NZ campaigners at a briefing at Parliament.
Former opposition spokesperson for Health Jonathan Coleman said at the time that the campaigners "misrepresent the science" and the event would "unfairly colour the debate".
Prime Minister Jacinda Ardern said many groups asked to brief MPs on issues and hosting them did not mean the Government agreed with their stance.
"It's just about letting people have their say regardless of whether we agree with them or not," she said at the time.