A local health authority's plans for the fluoridation of a city's tap water was not unlawful, the High Court ruled today.
A judge rejected accusations by Southampton resident Geraldine Milner that the decision-making process was "defective".
Mr Justice Holman, sitting in London, ruled there was no substance in any of the grounds of complaint and the legal challenge must be dismissed.
Ms Milner brought her application for judicial review backed by local anti-fluoride campaign groups.
The South Central Strategic Health Authority (SCSHA) used statutory powers to instruct Southern Water, the local water provider, to go ahead with fluoridation in February 2009.
Other local authorities had put other fluoridation schemes on hold pending the outcome of the case.
Refusing the claim for judicial review, the judge expressed sympathy for people like Ms Milner who disagreed with fluoridation but said he had not been able to conclude that there had been any illegality in the decision-making process.
He said: "I appreciate that that will deeply disappoint Ms Milner and the many objectors in the affected area, to whose position I am sympathetic.
"However it is important to stress that our democratic Parliament decided long ago that water can, in certain circumstances, be fluoridated.
"As I have endeavoured to show, and contrary perhaps to the belief of Ms Milner and others, it is not the law that fluoridation can only occur when a majority of the local population agree.
"Parliament has firmly entrusted area-specific decision making to the relevant strategic health authority (SHA).
"This SHA have not acted unlawfully and no court can interfere with their decision."
Ms Milner was not in court today because one of her children was sick.
The British Dental Association (BDA) welcomed the decision.
Professor Damien Walmsley, scientific adviser, said: "The BDA is pleased with the result because it is likely to encourage consultation on similar schemes in other parts of the country where fluoride could help address the poor dental health of the population.
"A recent European summary of the latest scientific evidence reiterated the view that water fluoridation is a safe and effective method of reducing oral health inequalities."