"The NHS is meant to be there for patients, any shape or size. I feel completely let down."
He had first visited the A&E unit at the University Hospital of Wales suffering from terrible tooth pain when a bone became caught in his teeth.
He was prescribed antibiotics for an abscess by an emergency dentist and was instructed to seek further treatment for gum disease.
He then visited St David's Hospital, which offers free check-ups.
Since being turned away Mr Keitley has been treating himself with painkillers.
In 2013 a dental company developed a chair that could cope with 71-stone patients in response to Britain's growing obesity epidemic.
The $45,000 Barico bariatric recliners are four times the price of standard seats.
David Vandyke, of UK supplier Bariatric Ltd, said at the time that the tide of obesity meant the seats were likely to become commonplace.
He added: "The Barico has a safe working load of 71 stone. Dental chairs at the moment have a safe working load of around 22 stone to 25 stone but they don't really work at those weights once a patient is sat back.
"It's something the NHS is very aware of and obesity is now classed under the Equality Act, which means everyone has the right to access services."
The patient claims he was not given any advice about where to seek other treatment.
Cardiff and Vale University Health Board, the group responsible for St David's Hospital, has been contacted for comment.
