Prof Seymour is the award-winning former dean of the Newcastle University School of Dental Sciences in the United Kingdom.
For the past 25 years he has also run a clinic focusing on the oral health of medically-compromised hospital patients, including transplant patients, at Newcastle.
He has been visiting the University of Otago School of Dentistry for the past two months as a Community Trust of Otago Visiting Professor, and says the Otago school is "highly regarded" by dental researchers in Britain.
About 550 individual medications contributed to dry mouth, he said.
Health authorities say that many groups of drugs, including some antidepressants and drugs to lower blood pressure, as well as some anti-epileptic, asthma and diuretic medications can contribute by reducing saliva supply.
"A dry mouth is not a healthy mouth," Prof Seymour said.
Saliva helps protect against some damaging micro-organisms, and teeth are prone to decay if the mouth is dry.
The population was ageing, people were keeping their teeth much longer and patients were often taking drugs for several medical conditions.
Dry mouth was the most common adverse drug side-effect on oral health, with patients finding it hard to talk or eat, in some severe cases.
Dentists had an important role to play by screening for possible adverse side-effects of medication, including among newly-available drugs, and reporting them.
"It's very much of a balancing act to achieve the best outcome for the patient."
Realism was also important, given that some patients with a mild dry mouth were being kept alive by blood pressure lowering drugs, he said.
Norman Firth, an oral pathologist at the Otago school, said that regular dental check-ups, advising the dentist of medication changes, drinking more water, and using sugar-free chewing gum could all help counter dry mouth.
There was growing awareness in New Zealand about drug interactions with oral health, but many patients might not realise their own specific medication could be contributing to dry mouth, he said.
