The County Court has ruled any tooth whitening technician who hands the patient a whitening tray is the practice of dentistry and must be done by the dentist.
Caroline Sumpter brought the case against Megawhite, who claimed their advanced laser tooth whitening technicians did not have to be dentists.
Ms Sumpter, herself a beauty therapist, was sold the ‘Megawhite Teeth Whitening Licence' under the pretence she did not have to be a dentist to carry out the treatment.
After being informed this was not the case, Ms Sumpter was awarded a full refund by the court.
Ms Sumpter said: "I am delighted at the ruling. I feel completely vindicated knowing this was not a legal procedure I could carry out, much to the denial of those behind the product.
"This case should serve as a warning for those currently offering similar types of treatment. It is illegal and cannot be tolerated any more."
The law clearly states tooth whitening products containing or releasing between 0.1 and six per cent hydrogen peroxide can now only be sold to a registered dental professional with the first application to be carried out under a dentist's supervision in the practice.
Chief Executive of the British Dental Health Foundation, Dr Nigel Carter OBE, said: "This is excellent news for those people looking to get their teeth whitened. Tooth whitening is a dental procedure as per the Dental Act 1984. Following the clarification of the law in 2013, these so-called whitening technicians have been seeking to exploit loopholes in the law to carry on offering the procedure illegally. This ruling should put an end to the debate once and for all.
"It is embarrassing that it has taken an individual to do what the GDC is failing to do and protect the public. It should not be left to individuals like Ms Sumpter to highlight the illegality of tooth whitening technicians. The regulatory body should be far more robust in their investigation process and protect the public from illegal tooth whiteners."
Dr Stuart Johnston from the British Dental Association added: "This makes it perfectly clear, that despite what those encouraging non-dentists to purchase their services and products say, tooth whitening is the practice of dentistry. This ensures patient safety with the correct techniques and safe evidence based products."
Both the British Dental Health Foundation and British Dental Association have been instrumental in helping to clarify the tooth whitening laws following the European Council's directive in 2013.
Alongside a number of other representatives, they have formed the Tooth Whitening Information Group, to educate and inform the public on how to achieve safe tooth whitening while also offering clear guidance to the dental, health and beauty profession on the regulations and to offer support to the relevant bodies who will be tackling illegal tooth whitening.
The Tooth Whitening Information Group played a significant role in helping Ms Sumpter's case by providing guidance during the trial.
Ms Sumpter added: "I am so grateful to the many people at the Tooth Whitening Information Group who have helped me along the way and I would like to thank them for the support they have provided for me throughout the case. The verdict comes as such a huge relief."
The other members of the group include the British Society of Dental Hygiene and Therapy, British Academy of Cosmetic Dentistry, British Association of Dental Nurses and the British Dental Bleaching Society.